Pediatric Cardiac CT in Congenital Heart Disease 3030748219, 9783030748210

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Pediatric Cardiac CT in Congenital Heart Disease Dilachew A. Adebo Editor

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Pediatric Cardiac CT in Congenital Heart Disease

Dilachew A. Adebo Editor

Pediatric Cardiac CT in Congenital Heart Disease

Editor Dilachew A. Adebo Division of Pediatric Cardiology The University of Texas Health Science Center Houston, TX USA

ISBN 978-3-030-74821-0    ISBN 978-3-030-74822-7 (eBook) https://doi.org/10.1007/978-3-030-74822-7 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Dedication to my wife, Senait, for her unconditional love and support. She is the best life partner and love of my life. Without her, this book would not be possible, nor my success as advanced imaging pediatric cardiologist. To my children: Nita, Deborah, and Samuel. Their constant encouragement has a special place in my heart. My deepest appreciation to my mother, Sulame, for her unique love and kindness To my late father, Achiko, who taught me respect, perseverance, self -discipline, and the value of life-long learning. He is smiling from above.

Foreword

Cardiologists, surgeons, and other health professionals caring for patients with congenital heart disease (CHD) nowadays can choose among a plethora of diagnostic imaging modalities to evaluate this growing population. Today’s reality is a culmination of a remarkable evolution since the humble beginning of the field of pediatric cardiac imaging approximately a century ago. Chest fluoroscopy was first performed in the early 1920s. The era of cardiac angiography followed the first right heart catheterization by Werner Forssmann, who catheterized himself in 1929. Frossmann’s daring proof-of-concept experiment, for which he was awarded the Nobel Prize in Medicine in 1956, ushered a series of advances in invasive cardiac imaging that allowed previously unimaginable visualization of the cardiac chambers and great vessels. However, there was little impetus to utilize risky diagnostic imaging procedures given that therapies had yet to be invented. The first congenital cardiac surgery by Dr. Robert E. Gross, who ligated the ductus arteriosus of 7-year-­ old Lorraine Sweeney at Boston Children’s Hospital in 1933, ushered in the era of treatment for CHD. Dr. Gross’s groundbreaking operation was soon followed by other advances, including the Brock procedure to alleviate pulmonary stenosis, the Blalock-Thomas-Taussig shunt to palliate cyanosis in patients with tetralogy of Fallot, and the first successful intracardiac correction of a congenital cardiac defect using hypothermia by Dr. F.  John Lewis(assisted by Dr. C. Walton Lillehei) in 1952. These breakthroughs in treatment have led to intense interest in diagnosis of CHD.  Cardiac catheterization was the mainstay of diagnostic imaging until the arrival of cardiac ultrasound in the 1970s. Following the pioneering work of Inge Edler and Hellmuth Hertz, who performed the first echocardiogram in 1953, the field of echocardiography has rapidly evolved. Cardiac MRI gained traction in the early 1990s. Though computed tomography (CT) technology was developed by Sir Godfrey Hounsfield in the early 1970s while he was an electrical engineer at EMI (he and Alan M. Cormack were jointly awarded the Nobel Prize in Medicine in 1979 for their work), cardiac CT was initially slow to be adopted for imaging of infants and children with CHD due to low spatial and temporal resolutions and dangerously high levels of radiation exposure. However, rapid technological advances in recent years have overcome these limitations, allowing modern CT scanners to image the heart in a fraction of a second with submillimeter spatial resolution and high temporal resolution, all with far lower levels of radiation exposure. By the

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second half of the 2010s, cardiac CT had become an essential part of the armamentarium of pediatric and congenital cardiac imagers. This book, edited by Dr. Dilachew A. Adebo, is a welcomed and timely new source of information for pediatric and congenital cardiologists, cardiac surgeons, radiologists, and healthcare professionals caring for this rapidly growing group of patients. With ever expanding options for diagnostic imaging of CHD, clinicians face a growing challenge in choosing the right test for the right patient at the right time. By describing a comprehensive approach to the evaluation of CHD by cardiac CT, the book provides an overview of how this rapidly evolving imaging technology can be effectively integrated into clinical practice. Boston Children’s Hospital Boston, MA, USA

Tal Geva, MD

Preface

Cardiac imaging plays a key role in the accurate diagnosis of pediatric congenital heart disease (CHD). Cardiac CT is increasingly being used for the evaluation of cardiovascular structures in infants and children with CHD. The prevalence of patients with congenital heart disease is rapidly increasing as a result of improved outcomes of medical, surgical, and catheter-based treatment strategies. Despite advances in new computed tomography techniques with radiation dose reduction, there is no comprehensive textbook on pediatric cardiac CT in congenital heart disease. Physicians involved in performing and reading cardiac CT in congenital heart disease should have expertise in pediatric cardiac CT, including knowledge of ECG gating techniques, contrast injection, and image acquisition protocols specific to pediatric congenital heart disease. Selection of the acquisition parameters, calculating contrast dose and identifying contrast delivery technique, and use of dose reduction strategies are important part of patient preparation and cardiac CT technique. This textbook provides a comprehensive and integrated approach to the pediatric cardiac CT evaluation in congenital heart disease. To this end, we have opted to combine the technical aspects of pediatric cardiac CT with in-­ depth disease-specific evaluation of the different forms of congenital heart disease with particular focus on preoperative and postoperative evaluation. Pediatric cardiac CT does not only accurately demonstrate the intracardiac anatomy in complex CHD, and vascular anomalies, but also allows evaluation of lungs, airways, soft tissues, and osseous structures. Prevalence of clinically significant extracardiac finding is common; hence, physician reading CT angiography studies of pediatric congenital heart disease patients should be aware of possible significant findings that occur outside the heart and, therefore, should follow a systematic approach in the reading of such studies. This will help to ensure that important findings are not missed, necessary clinical management is implemented, and unnecessary follow-up examinations are avoided. Hence, this textbook covers non-cardiac findings of pediatric cardiac CT as well. This textbook also describes role of cardiac CT to provide superior image quality for three-dimensional modelling, image fusion with fluoroscopy or merged to electroanatomic mapping to precisely visualize complex anatomy and guide intervention for better outcome. I hope that Pediatric Cardiac CT in Congenital Heart Disease will be a great resource for those who utilize this imaging approach in the care of ix

Preface

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p­ ediatric patients with congenital heart disease. It is also my hope that this textbook will stimulate the reader about this fascinating and ever-expanding field and prove future advances. Houston, TX, USA

Dilachew A. Adebo

Acknowledgments

The editor would like to thank the individual authors for the hard work and dedication; without your contributions, this unique textbook would not have been possible. Of course, thanks to all my colleagues at Children’s Heart Institute, Children’s Memorial Hermann Hospital/McGovern Medical School, for their unique support for this work. The authors also thank the staff at Springer, particularly Margaret Moore, Rekha Udaiyar, and Jeffrey Taub for their helpfulness at each stage of the publication of this book.

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Contents

1 Advantages of Cardiac CT Scan over Other Diagnostic Techniques ��������������������������������������������������������������������   1 Dilachew A. Adebo 2 Techniques of Cardiac CT Scan: Patient Preparation, Contrast Medium, Scanning, and Post-Processing ����������������������  15 Dilachew A. Adebo 3 Evaluation of Cardiac Malposition, Cardiac Segmental Approach, and Heterotaxy Syndrome��������������������������������������������  23 Mehul D. Patel 4 Systemic Venous Anomalies������������������������������������������������������������  37 Santosh C. Uppu 5 Anomalous Pulmonary Venous Connections and Cor Triatriatum������������������������������������������������������������������������  43 Li Xiong 6 Septal Defects: Atrial Septal Defects, Ventricular Septal Defects, Atrioventricular Septal Defects, and Unroofed Coronary Sinus��������������������������������������������������������  55 Mehul D. Patel 7 Atrioventricular Valves: Tricuspid Valve��������������������������������������  63 Santosh C. Uppu 8 Atrioventricular Valves: Congenital Mitral Valve Abnormalities ������������������������������������������������������������������������  69 Santosh C. Uppu 9 Atrioventricular Connections: Double-Inlet Ventricle, Atrioventricular Discordance, and Congenitally Corrected Transposition of Great Arteries������������������������������������  75 Rami Kharouf and Dilachew A. Adebo 10 Right Ventricular Outflow Tract: Pulmonary Valve Stenosis ��������������������������������������������������������������  81 Dilachew A. Adebo

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11 Right Ventricular Outflow Tract: Pulmonary Atresia with Intact Ventricular Septum������������������������������������������������������  85 Dilachew A. Adebo 12 Right Ventricular Outflow Tract: Pulmonary Valve Atresia, Ventricular Septal Defect, and Major Aortopulmonary Collateral Arteries����������������������������������������������������������������������������  89 Dilachew A. Adebo 13 Right Ventricular Outflow Tract: Tetralogy of Fallot������������������  95 Dilachew A. Adebo 14 Right Ventricular Outflow Tract: Absent Pulmonary Valve Syndrome�������������������������������������������������������������������������������� 103 Dilachew A. Adebo 15 Left Ventricular Outflow Tract: Congenital Aortic Valve and Left Ventricular Outflow Anomalies���������������������������� 107 Santosh C. Uppu 16 Left Ventricular Outflow Tract: Hypoplastic Left Heart Syndrome ���������������������������������������������������������������������� 115 Santosh C. Uppu and Mehul D. Patel 17 Double-Outlet Right Ventricle�������������������������������������������������������� 121 Laura Schoeneberg and Dilachew A. Adebo 18 Dextro-Transposition of the Great Arteries���������������������������������� 129 Laura Schoeneberg and Dilachew A. Adebo 19 Truncus Arteriosus�������������������������������������������������������������������������� 137 Laura Schoeneberg and Dilachew A. Adebo 20 Anomalous Aortic Origin of Pulmonary Arteries ������������������������ 143 Laura Schoeneberg and Dilachew A. Adebo 21 Anomalous Coronary Arteries�������������������������������������������������������� 147 Li Xiong 22 Aneurysm of the Sinus of Valsalva, Aortic-Left Ventricular Tunnel �������������������������������������������������������������������������� 159 Dilachew A. Adebo 23 Aortopulmonary Window �������������������������������������������������������������� 163 Dilachew A. Adebo 24 Aortic Arch Anomalies: Coarctation of the Aorta and Aortic Arch Hypoplasia������������������������������������������������������������ 167 Elisa Rhee and Dilachew A. Adebo 25 Aortic Arch Anomalies: Aortic Arch Interruption������������������������ 175 Elisa Rhee and Dilachew A. Adebo 26 Vascular Rings and Slings �������������������������������������������������������������� 181 Arpit K. Agarwal

Contents

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27 Cardiac Tumors�������������������������������������������������������������������������������� 197 Santosh C. Uppu 28 Cardiac Computed Tomography After Single Ventricle Palliation�������������������������������������������������������������������������� 205 Sheba John and Dilachew A. Adebo 29 Cardiac Computed Tomography in Evaluation of Ventricular Function ������������������������������������������������������������������ 213 Rami Kharouf and Dilachew A. Adebo 30 Role of Cardiac CT in Preopertaive and Postoperative Evaluation of Congenital Heart Defects in Children�������������������� 219 Antonio F. Corno and Jorge D. Salazar 31 Non-cardiac Findings of Cardiac CT�������������������������������������������� 269 Dilachew A. Adebo Index���������������������������������������������������������������������������������������������������������� 275

Contributors

Dilachew  A.  Adebo, MD, FAAP, FACC, FSCMR Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA Arpit K. Agarwal, MD  Baylor College of Medicine, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, San Antonio Children’s Hospital, San Antonio, TX, USA Antonio F. Corno, MD, FRCS, FACC, FETCS  Children’s Heart Institute, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA Sheba  John, MD Division of Pediatric Cardiology, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA Rami  Kharouf, MD Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA Mehul  D.  Patel, MD Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA Elisa Rhee, MD  Children’s Heart Institute, Division of Pediatric Cardiology, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA Jorge D. Salazar, MD  Division of Pediatric and Congenital Heart Surgery, Children’s Heart Institute, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA Children’s Heart Institute, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA

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Laura Schoeneberg, MD  Children’s Heart Institute, Division of Pediatric Cardiology, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA Santosh  C.  Uppu, MD Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA Li Xiong, MD  Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA

Contributors

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Advantages of Cardiac CT Scan over Other Diagnostic Techniques Dilachew A. Adebo

Introduction

of the heart, it is time-consuming and often requires lengthy sedation; therefore, the use of Congenital heart disease is generally evaluated MRI in seriously ill newborns or young infants is with the use of echocardiography, catheter angi- usually restricted. Cardiac MRI is also highly ography, and magnetic resonance imaging (MRI). susceptible to metallic artifacts. There is a greater However, low-dose multidetector computed need for cardiac CT with the increased use of tomographic angiography is being increasingly electrophysiology devices that may be MRI used [1–3]. Transthoracic echocardiography unsafe and higher prevalence of metallic implants image quality may be suboptimal due to poor that adversely affect MRI image quality. Cardiac acoustic window. Echocardiography also has CT delineates the cardiovascular anatomy well in limited depiction of extracardiac vascular struc- patients with metallic implants in the body tures. Catheter angiography produces overlap- (Figs. 1.1, 1.2, 1.3, and 1.4). ping views of adjacent vascular structures, Non-cardiovascular anatomy, including aircausing difficulty in the simultaneous depiction way, lung parenchyma, and skeletal anatomy, is of the systemic and pulmonary vascular systems, clearly seen (Fig.  1.5). Cardiovascular CT also leads to undesirable catheter-related sequelae provides excellent visualization of stents, con(vascular injury), and delivers relatively high duits, and metallic objects and can be performed doses of ionizing radiation [2, 3]. Given the in patients with implanted pacemakers and defishortcomings in transthoracic echocardiography brillators [4]. in delineating the extent of extracardiac vascular Cardiovascular CT is increasingly used as an structures and the morbidities associated with adjunct to echocardiography when cardiac MRI catheter angiography, there is interest in non-­ is considered high risk, contraindicated, or invasive imaging modalities to address this diag- unlikely to provide images with suitable quality nostic challenge. Even though MRI is eminently to answer the clinical question [5, 6]. capable in the anatomic and functional evaluation Coronary anomalies are common in patients with CHD, and precise anatomic definition prior to surgical intervention is often indicated since it D. A. Adebo (*) may affect the surgical outcome [7]. Coronary Children’s Heart Institute, Division of Pediatric CT angiography in patients of all ages with coroCardiology, Non-Invasive Cardiac Imaging, nary anomalies is well described and has superior Children’s Memorial Hermann Hospital, McGovern accuracy in visualizing the coronary arteries [8– Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA 17]. CMR has been shown to be useful for e-mail: [email protected]

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_1

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D. A. Adebo

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a

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RV-PA

LPA RV-PA

RV

Fig. 1.1  A 5-year-old male patient after repaired tetralogy of Fallot and stented right ventricular to pulmonary artery conduit. Cardiac CT shows patent right ventricular to pulmonary artery conduit with mildly hypoplastic left pulmonary artery. His echocardiographic images were affected due to poor acoustic window. Cardiac CT was

performed due to metallic artifact concern on cardiac MRI. Parasagittal reconstructed image (a) and 3D volume rendered reconstruction (b). RV-PA, stented right ventricular to pulmonary artery conduit; LPA left pulmonary artery, RV right ventricle

c­ ongenital coronary anomalies in older children and adolescents but is less useful in the youngest patients because image quality is inversely related to both patient age and heart rate [18, 19]. Distal coronary artery evaluation by cardiac MRI is often unreliable in young patients. Cardiac CT is the preferred imaging modality to delineate coronary arteries in young patients (Fig. 1.6). Cardiac CT is the best imaging modality for suspected vascular rings and slings for evaluation of the vascular anatomy and associated tracheobronchial narrowing (Fig. 1.5). The ability of cardiac CT to simultaneously image vascular structures and airways makes it superior imaging modality for symptomatic patients requiring surgical intervention [20–30]. Cardiac CT reliably visualizes aortopulmonary collateral arteries in patients with pulmonary atresia and ventricular septal defect (Fig. 1.7). In comparison to conventional angiography, cardiovascular CT has excellent accuracy in defining aortopulmonary collaterals in these patients prior to surgical unifocalization [31–33]. Cardiac CT is also superior imaging modality in patients with absent pulmonary valve syndrome where dilated branch pulmonary arteries may compress the airways [27].

Cardiac CT is the best imaging modality for patients with anomalous pulmonary venous return to guide management in both pre-­ intervention and post-intervention patients (Fig. 1.8). In summary, the advantages of cardiac CT include high spatial resolution, less or no need for sedation, more optimal evaluation in patients with metallic stents and conduits, superior evaluation of calcification, and better evaluation of airways and lung parenchyma.

 ardiac CT Image Fusion C with Fluoroscopy to Guide Cardiac Catheterization Image fusion of cardiac CT with fluoroscopic images has been used during interventional cardiac catheterization [34–36]. The use of fluoroscopy alone limits the ability of the interventionalist to reliably identify the area of cardiac defect. However, fusion of cardiac CT images with fluoroscopy (Fig.  1.9) improves the preprocedural planning and intraprocedural guidance. This significantly decreases radiation exposure with more accurate and safe intervention.

1  Advantages of Cardiac CT Scan over Other Diagnostic Techniques

 pplication of Cardiac CT A in Electrophysiology Intervention Cardiac CT has evolved into a practical and valuable imaging modality and is being increasingly used in electrophysiology intervention. It can be used to depict the anatomy and assist in guiding the procedure which makes such procedures quicker, safer, and more effective [37]. Cardiac CT images are commonly used in pulmonary vein isolation procedure for pulmonary vein origin atrial tachycardia (Fig.  1.10) or as roadmap for ablation of ventricular tachycardia

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originating from the right ventricular outflow tract (Fig. 1.11).

 ardiac CT Images for Three-­ C Dimensional Modeling of Complex Congenital Heart Disease Cardiac CT gives superior and high spatial resolution images for three-dimensional modeling. The cardiac CT images can be used for virtual three-dimensional modeling (Fig. 1.12) or three-­ dimensional printing (Fig.  1.13) to precisely

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AAO

AAO RPA

DAO

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Fig. 1.2  A 4-year-old male patient with Williams syndrome, coarctation of the aorta, and branch pulmonary artery stenosis with multiple stents in his aortic arch and branch pulmonary arteries. Parasagittal (a), axial (b), coronal (c), and 3D volume rendered reconstructed images

(d) show mildly hypoplastic stented aortic arch and branch pulmonary arteries (arrows). AAO ascending aorta, DAO descending thoracic aorta, RPA stented right pulmonary artery, LPA stented left pulmonary artery, LV left ventricle, RV right ventricle

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AAO

DAO DAO

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AAO

AAO

DAO DAO

Fig. 1.3  A 6-year-old male patient with hypoplastic thoracic aorta of unknown etiology. Pre-intervention cardiac CT in coronal (a) and 3D volume rendered reconstruction (b) showing severe long-segment hypoplasia of mid-­ thoracic descending aorta (single arrow). Follow-up car-

diac CT (c, d) performed after stent placement shows mildly hypoplastic stented site (double arrows) with residual narrowing at distal end of the stent. AAO ascending aorta, DAO descending thoracic aorta

1  Advantages of Cardiac CT Scan over Other Diagnostic Techniques

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b LPA LPA

FC

FC RA

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LPA FC RA

IVC

Fig. 1.4  A 5-year-old patient with tricuspid valve atresia after Fontan procedure and left pulmonary artery stenosis requiring stent placement to left pulmonary artery. Cardiac CT with coronal reconstructed image (a) and 3D volume rendered reconstruction (b) showing mildly hypoplastic

stented left pulmonary artery (LPA). Delayed venous phase acquisition (c) shows no evidence of filling defect or thrombus. LPA left pulmonary artery, FC Fontan conduit, IVC inferior vena cava, RA right atrium

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RAA RM

LM

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DAO

Fig. 1.5  Infant with double aortic arch. Cardiac CT with coronal (a), axial (b), and three-dimensional volume rendered reconstruction (c) showing double aortic arch with mild narrowing of distal trachea (arrow). T trachea, RM

Fig. 1.6  Neonate with dextro-transposition of great arteries and anomalous coronary arteries. Cardiac CT 3D volume rendered reconstructed image shows single coronary artery system (arrow) which arises from anterior sinus and divides into the left main and right coronary artery. Cardiac CT is the best imaging modality for anomalous coronary arteries in newborns. AO aortic root

right main stem bronchus, LM left mainstem bronchus, RAA right aortic arch component, LAA left aortic arch component, DAO descending thoracic aorta. Cardiac CT is the best imaging modality to evaluate airways

1  Advantages of Cardiac CT Scan over Other Diagnostic Techniques

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DAO

DAO

Fig. 1.7  Neonate with pulmonary atresia, ventricular septal defect, and major aortopulmonary collaterals. Cardiac CT with coronal reconstructed image (a) and 3D volume rendered reconstruction (b) showing large-sized

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aortopulmonary collateral (arrows) arising from left lateral aspect of descending thoracic aorta. DAO descending thoracic aorta

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LPA

LPV

RPV

LPV VV

VV

Fig. 1.8  Neonate with mixed total anomalous pulmonary venous return. Cardiac CT with coronal reconstructed image (a) and 3D volume rendered reconstruction (b) showing the individual pulmonary veins and hypoplastic segment in the middle (arrow) which was difficult to

delineate on echocardiography. VV descending vertical vein, RPV right pulmonary vein, LPV left pulmonary vein, RPA right pulmonary artery, LPA left pulmonary artery

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c PVC

LA

LA

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Fig. 1.9  Infant after repaired total anomalous pulmonary venous return with residual narrowing at site of anastomosis of pulmonary venous confluence to the left atrium (arrow). Cardiac CT axial (a) and coronal (b) reconstructed images. Pre-fusion fluoroscopy image (c) and

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segmentation of the CT images (d). The fusion of cardiac CT and fluoroscopy images (e, f, g) used as a guide for catheter manipulation and balloon angioplasty of the narrowest site of the pulmonary vein confluence at its left atrial junction (yellow circle on fused images)

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a

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Fig. 1.10  Segmented cardiac CT model of the left atrium and pulmonary veins along with coronary sinus and superior vena cava (a). This image is merged to electroanatomic mapping reconstructed image of the left atrium and pulmonary veins (b) to accurately and safely isolate

(ablate) pulmonary vein focus atrial tachycardia (arrows). LSPV left upper pulmonary vein, LIPV left lower pulmonary vein, CS coronary sinus, SVC superior vena cava, LAA left atrial appendage

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RVOT

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RV

Fig. 1.11  Segmented cardiac CT model of the right heart structures for preprocedural planning before ablation of ventricular tachycardia originating from right ventricular outflow tract. RVOT right ventricular outflow tract, MPA main pulmonary artery, RV right ventricle, RA right atrium, SVC superior vena cava

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MPA

AO

AO MPA

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RV

Fig. 1.12 Infant with double-outlet right ventricle, dextro-­ malposed great arteries and remote ventricular septal defect with both great arteries arising from right ventricle. Computer-assisted virtual three-dimensional model shows route of virtual conduit from remote ven-

tricular septal defect to aortic outflow (a). Modified sagittal reconstructed image of right ventricular outflow tract (b). RV right ventricle, AO aortic root, MPA main pulmonary artery

1  Advantages of Cardiac CT Scan over Other Diagnostic Techniques

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b MPA

MPA AO

RV

LV

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Fig. 1.13 Infant with double-outlet right ventricle, dextro-­ malposed great arteries and remote ventricular septal defect with subaortic stenosis due to deviated conal septum (arrowhead). Computer-assisted virtual patch closure of the ventricular septal defect (arrows) for surgical

planning. Coronal reconstructed image of right ventricular outflow tract (a). Computer-assisted virtual three-­ dimensional model (b). Three-dimensional printed model (c). RV right ventricle, LV left ventricle, AO aortic root, MPA main pulmonary artery

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visualize complex anatomy, plan surgical procedures, and teach trainees and patients [38–42].

References 1. Dodge-Khatami J, Adebo DA. Evaluation of complex congenital heart disease in infants using low dose cardiac computed tomography. Int J Cardiovasc Imaging. 2021. https://doi.org/10.1007/s10554-­020-­02118-­7. 2. Vyas HV, Greenberg SB, Krishnamurthy R. MR imaging and CT evaluation of congenital pulmonary vein abnormalities in neonates and infants. Radiographics. 2012;32(1):87–98. 3. Han BK, Overman DM, Grant K, et al. Non-sedated, free breathing cardiac CT for evaluation of complex congenital heart disease in neonates. J Cardiovasc Comput Tomogr. 2013;7(6):354–60. 4. Khairy P, Van Hare GF, Balaji S, et al. PACES/HRS Expert Consensus Statement on the recognition and management of arrhythmias in adult congenital heart disease. Heart Rhythm. 2014;11:102–65. 5. Prakash A, Powell AJ, Geva T.  Multimodality noninvasive imaging for assessment of congenital heart disease. Circ Cardiovasc Imaging. 2010;3:112–25. 6. Han BK, Lesser AM, Vezmar M, et al. Cardiovascular imaging trends in congenital heart disease: a single center experience. J Cardiovasc Comput Tomogr. 2013;7:361–6. 7. Yu FF, Lu B, Gao Y, et  al. Congenital anomalies of coronary arteries in complex congenital heart disease: diagnosis and analysis with dual-source CT.  J Cardiovasc Comput Tomogr. 2013;7:383–90. 8. Attili A, Hensley AK, Jones FD, Grabham J, DiSessa TG.  Echocardiography and coronary CT angiography imaging of variations in coronary anatomy and coronary abnormalities in athletic children: detection of coronary abnormalities that create a risk for sudden death. Echocardiography. 2013;30:225–33. 9. Kaushal S, Backer CL, Popescu AR, et al. Intramural coronary length correlates with symptoms in patients with anomalous aortic origin of the coronary artery. Ann Thorac Surg. 2011;92:986–91. 10. Lee HJ, Hong YJ, Kim HY, et al. Anomalous origin of the right coronary artery from the left coronary sinus with an interarterial course: subtypes and clinical importance. Radiology. 2012;262:101–8. 11. Cheng Z, Wang X, Duan Y, et al. Detection of coronary artery anomalies by dual-source CT coronary angiography. Clin Radiol. 2010;65:815–22. 12. Schmitt R, Froehner S, Brunn J, et  al. Congenital anomalies of the coronary arteries: imaging with contrast-­enhanced, multidetector computed tomography. Eur Radiol. 2005;15:1110–21. 13. Shi H, Aschoff AJ, Brambs HJ, Hoffmann MH.  Multislice CT imaging of anomalous coronary arteries. Eur Radiol. 2004;14:2172–81. 14. Zhang LJ, Wu SY, Huang W, Zhou CS, Lu GM.  Anomalous origin of the right coronary artery

D. A. Adebo originating from the left coronary sinus of valsalva with an interarterial course: diagnosis and dynamic evaluation using dual-source computed tomography. J Comput Assist Tomogr. 2009;33:348–53. 15. Lee BY, Song KS, Jung SE, et  al. Anomalous right coronary artery originated from left coronary sinus with interarterial course: evaluation of the proximal segment on multidetector row computed tomography with clinical correlation. J Comput Assist Tomogr. 2009;33:755–62. 16. Opolski MP, Pregowski J, Kruk M, et al. Prevalence and characteristics of coronary anomalies originating from the opposite sinus of Valsalva in 8,522 patients referred for coronary computed tomography angiography. Am J Cardiol. 2013;111:1361–7. 17. Miller JA, Anavekar NS, El Yaman MM, Burkhart HM, Miller AJ, Julsrud PR.  Computed tomographic angiography identification of intramural segments in anomalous coronary arteries with interarterial course. Int J Cardiovasc Imaging. 2012;28:1525–32. 18. Beerbaum P, Sarikouch S, Laser KT, Greil G, Burchert W, Korperich H.  Coronary anomalies assessed by whole-heart isotropic 3D magnetic resonance imaging for cardiac morphology in congenital heart disease. J Magn Reson Imaging. 2009;29:320–7. 19. Prakken NH, Cramer MJ, Olimulder MA, Agostoni P, Mali WP, Velthuis BK.  Screening for proximal coronary artery anomalies with 3-dimensional MR coronary angiography. Int J Cardiovasc Imaging. 2010;26:701–10. 20. Ramos-Duran L, Nance JW Jr, Schoepf UJ, Henzler T, Apfaltrer P, Hlavacek AM. Developmental aortic arch anomalies in infants and children assessed with CT angiography. Am J Roentgenol. 2012;198:W466–74. 21. Di Sessa TG, Di Sessa P, Gregory B, Vranicar M. The use of 3D contrast enhanced CT reconstructions to project images of vascular rings and coarctation of the aorta. Echocardiography. 2009;26:76–81. 22. Yang DH, Goo HW, Seo DM, et  al. Multislice CT angiography of interrupted aortic arch. Pediatr Radiol. 2008;38:89–100. 23. Lee EY, Siegel MJ. MDCT of tracheobronchial narrowing in pediatric patients. J Thorac Imaging. 2007;22:300–9. 24. Lee EY, Zurakowski D, Waltz DA, et al. MDCT evaluation of the prevalence of tracheomalacia in children with mediastinal aortic vascular anomalies. J Thorac Imaging. 2008;23:258–65. 25. Jhang WK, Park JJ, Seo DM, Goo HW, Gwak M.  Perioperative evaluation of airways in patients with arch obstruction and intracardiac defects. Ann Thorac Surg. 2008;85:1753–8. 26. An HS, Choi EY, Kwon BS, et al. Airway compression in children with congenital heart disease evaluated using computed tomography. Ann Thorac Surg. 2013;96:2192–7. 27. Zhong YM, Jaffe RB, Liu JF, et al. Multi-slice computed tomography assessment of bronchial compression with absent pulmonary valve. Pediatr Radiol. 2014;44:803–9.

1  Advantages of Cardiac CT Scan over Other Diagnostic Techniques 28. Lee KS, Boiselle PM. Update on multidetector computed tomography imaging of the airways. J Thorac Imaging. 2010;25:112–24. 29. Watanabe N, Hayabuchi Y, Inoue M, et  al. Tracheal compression due to an elongated aortic arch in patients with congenital heart disease: evaluation using multidetector-­ row CT.  Pediatr Radiol. 2009;39:1048–53. 30. Jiao H, Xu Z, Wu L, et al. Detection of airway anomalies in pediatric patients with cardiovascular anomalies with low dose prospective ECG-gated dual source CT. PLoS One. 2013;8:82826. 31. Hayabuchi Y, Inoue M, Watanabe N, et al. Assessment of systemic-pulmonary collateral arteries in children with cyanotic congenital heart disease using multidetector-row computed tomography: comparison with conventional angiography. Int J Cardiol. 2010;138:266–71. 32. Meinel FG, Huda W, Schoepf UJ, et  al. Diagnostic accuracy of CT angiography in infants with tetralogy of Fallot with pulmonary atresia and major aortopulmonary collateral arteries. J Cardiovasc Comput Tomogr. 2013;7:367–75. 33. Greil GF, Schoebinger M, Kuettner A, et  al. Imaging of aortopulmonary collateral arteries with high-­ resolution multidetector CT.  Pediatr Radiol. 2006;36:502–9. 34. Auricchio A, Sorgente A, Soubelet E, et al. Accuracy and usefulness of fusion imaging between three-­ dimensional coronary sinus and coronary veins computed tomographic images with projection images obtained using fluoroscopy. Europace. 2009;11:1483–90. 35. Krishnaswamy A, Tuzcu EM, Kapadia SR.  Three-­ dimensional computed tomography in the cardiac

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catheterization laboratory. Catheter Cardiovasc Interv. 2011;77:860–5. 36. Chad Kliger MD, Vladimir Jelnin MD, Sonnit Sharma MD, et  al. CT angiography-fluoroscopy fusion imaging for percutaneous transseptal access. JACC Cardiovasc Imaging. 2014;7:169–77. 37. Duckett SG, Ginks MR, Knowles BR, et al. Advanced image fusion to overlay coronary sinus anatomy with real-time fluoroscopy to facilitate left ventricular lead implantation in CRT.  Pacing Clin Electrophysiol. 2011;34:226–34. 38. Shiraishi I, Yamagishi M, Hamaoka K, Fukuzawa M, Yagihara T.  Simulative operation on congenital heart disease using rubber like urethane stereolithographic biomodels based on 3D datasets of multislice computed tomography. Eur J Cardiothorac Surg. 2010;37:302–6. 39. Valverde I, Gomez-Ciriza G, Hussain T, et al. Three-­ dimensional printed models for surgical planning of complex congenital heart defects: an i­nternational multicentre study. Eur J Cardiothorac Surg. 2017;52:1139–48. 40. Yim D, Dragulescu A, Ide H, et al. Essential modifiers of double outlet right ventricle: revisit with endocardial surface images and 3-dimensional print models. Circ Cardiovasc Imaging. 2018;11:006891. 41. Yoo SJ, van Arsdell GS. 3D printing in surgical management of double outlet right ventricle. Front Pediatr. 2018;5:289. 42. Hoashi T, Ichikawa H, Nakata T, et  al. Utility of a super-flexible three-dimensional printed heart model in congenital heart surgery. Interact Cardiovasc Thorac Surg. 2018;27:749–55.

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Techniques of Cardiac CT Scan: Patient Preparation, Contrast Medium, Scanning, and Post-Processing Dilachew A. Adebo

Introduction

in using the exam for management decision-­ making. Contrast medium delivery becomes an Cardiac imaging plays a key role in the accurate essential means to accommodate increased noise diagnosis of pediatric congenital heart disease and maintain a diagnostic contrast-to-noise ratio. (CHD). Cardiac CT is increasingly being used Selection of the acquisition parameters, calculatfor the evaluation of cardiovascular structures in ing contrast dose and identifying contrast delivinfants and children with CHD [1–19]. Fast scan ery technique, and use of dose reduction strategies speeds and increased anatomic coverage, com- are important part of patient preparation and carbined with a flexible ECG-synchronized scan and diac CT technique. low radiation dose, are of critical importance in The clinical use of cardiac CT in congenital improving the image quality of cardiac CT scans heart disease is evolving rapidly. The prevalence and minimizing patient risks [1–4]. The rapid of patients with congenital heart disease is rapimage acquisition eliminates or reduces the need idly increasing as a result of improved outcomes for sedation and anesthesia in those unable to of medical, surgical, and catheter-based treatcooperate with short breath hold [4]. In the ment strategies [5–19]. There is a greater need for author’s practice, cardiac CT has become part of cardiac CT with increased use of electrophysiolroutine evaluation of seriously ill newborns and ogy devices that may be MRI unsafe and higher infants with complex CHD when a clinical ques- prevalence of metallic implants that adversely tion cannot be answered by echocardiography. affect magnetic resonance imaging (MRI) image The newer-generation multidetector and dual-­ quality. For older patients, echocardiography is source CT scanners provide fast scan with usually insufficient to answer the clinical increased anatomic coverage, low radiation dose, question. and acceptable noise. It is important to reach a balance, as excessive noise may diminish the accuracy of exam interpretation and confidence Patient Preparation and Contrast

Medium

D. A. Adebo (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

For all requested exams, initial screening needs to first verify that cardiac CT is the preferred option for the imaging question to be answered. Reviewing both prenatal and postnatal echocardiographic information, inpatient or outpatient

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_2

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clinic notes, and any prior surgical or interventional procedure notes is crucial to plan the scan and contrast administration. Confirming a normal renal function for suspected or known renal disease and absence of allergies to iodinated contrast or related products is very important. If a patient has abnormal renal function and is on hemodialysis or peritoneal dialysis, the exam may be performed prior to scheduled dialysis. Pregnancy testing is indicated in post-menarchal females prior to cardiac CT imaging. Institutional guidelines should be followed. The location of venous access depends on the suspected lesion and age and size of the patient. In neonates, infants, and toddlers, a lower-­ extremity peripheral intravenous line is preferred to evaluate aortic arch, pulmonary arteries, or infracardiac anomalous pulmonary venous return. Contrast injection from lower extremity avoids streak artifact in the aortic root, arch vessels, or branch pulmonary arteries due to residual high-density contrast in the superior vena cava or innominate veins. The right antecubital location is the preferred access site for older children. The optimal location of a peripheral IV may vary by cardiac lesion. To assess a known or suspected persistent left superior vena cava, contrast is preferably injected from the left upper extremity. If an interrupted inferior vena cava is suspected, contrast injection in the lower extremity will guarantee that the structure is well opacified and azygous continuation draining to the superior vena cava will be well visualized. Adequate size peripheral venous catheter gauge allows to administer the contrast with good flow rates to achieve optimal contrast-to-noise ratio [22]. Generally, 22- or 24-gauge peripheral venous catheter is used in neonates and infants, and 18- or 20-gauge catheters are used for older children and young adults. The optimal power injector pressure is 50–100 PSI (pounds per square inch) for 24-gauge peripheral intravenous catheter and 100–300 PSI for 18-gauge catheter [4, 23]. Rarely central venous catheters can be used to administer the contrast. Hand injection is preferably used with central venous catheters. Power injection through central lines not specifi-

D. A. Adebo

cally designed for power injection is not recommended by the FDA or central line manufacturers. Power injection through central lines can be safely performed if pressure-limited injection is employed [24]. It is very important to verify the maximum allowed PSI in the package insert or hub of the catheter before injecting contrast via central venous catheter. Umbilical venous catheters can be safely used but may result in suboptimal contrast enhancement due to reflux of contrast into the liver. Patients with complex congenital heart disease may have intracardiac shunts; hence, it is very important to avoid any air bubbles in the injection which may result in systemic arterial embolus. Contrast swirling with unopacified blood during image acquisition can be difficult to differentiate from thrombus or venous occlusion in patients after single-ventricle palliation (e.g., bidirectional Glenn or after Fontan procedure) where delayed venous phase acquisition delineates the anatomy better. If an antecubital intravenous catheter is in place, efforts should be made to prevent elbow flexion with contrast injection. This can be achieved with an arm board or with tight swaddling. If an infant or small child is scanned without sedation, a strap across the patient on the CT table will prevent movement between localizer images and the main acquisition. A sucrose-flavored pacifier may be used to calm young infants during the study [26]; hence, there will be no or minimal need for sedation and anesthesia. Topical anesthetic or child life support can be used to comfort older children. With newer-generation scanners, cardiac CT can be performed with no or minimal sedation for evaluation of congenital heart disease in neonates, infants, and children [1, 13, 15–20]. However, for older-generation scanners with images acquired over several seconds or multiple heart beats, breath holding may be required to reduce motion artifact, particularly when trying to image small cardiac structures like coronary arteries. Most patients 7  years of age or older who are developmentally appropriate for age can cooperate with a breath hold. For those able to

2  Techniques of Cardiac CT Scan: Patient Preparation, Contrast Medium, Scanning, and Post-Processing

cooperate, practicing the breath hold with the patient prior to imaging is often helpful both to assure cooperation (alleviates anxiety) and to assess the respiratory variability of the heart rate. For detailed evaluation of coronary arteries (ostial anatomy) or ventricular function, patients younger than 6  years of age may need general anesthesia for breath holding. For hemodynamically stable patients who require evaluation of small cardiac structures like coronary arteries [25] and major aortopulmonary collateral arteries, dexmedetomidine or betablocker can be used to slow down the heart rate and improve image quality [1, 27–33]. Sublingual nitroglycerin has been shown to increase coronary volumes and lumen diameters on coronary CT angiography in adult patients. Nitroglycerin should be avoided if the patient has been on a phosphodiesterase type 5 inhibitor [34]. To obtain good image quality with low radiation exposure and low image noise, patients should be positioned at the scanner isocenter with the patient in the middle of the CT gantry [20]. Positioning the arms above the head also improves image quality. Keeping the arms down can create artifact when using low kV scanning and can cause the automated exposure control (if used) to increase the tube current to account for the arms [21]. Iso-osmolar, non-ionic, and water-soluble contrast agent is preferred in young infants. Of note, prior to injecting contrast, a saline test injection is administered at the designated cardiac CT flow rate using power injector to assess the peripheral intravenous catheter adequacy and confirm that the exam can proceed safely. It is important to check injection site and the PSI during test injection. In author’s practice, direct connection between the power injector and the hub of the peripheral intravenous access is used. For patient with pacemaker device, the pacemaker device must be interrogated to identify the underlying rate and rhythm [35]. This helps decide if any pacemaker rate adjustment is needed before the scan. The preferred approach is to image the patient during either the normal or paced rhythm, but not with a combination of both. It is important to turn off the activity mode

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in order to avoid an inadvertent increase in heart rate related to pacemaker generator motion or increased breathing. A pre-scan timing bolus is rarely used in pediatric cardiac CT since it uses some of the total contrast available for the angiogram and results in additional radiation exposure. There are different contrast injection protocols in practical use: triphasic injection protocol (biventricular injection protocol) and biphasic injection protocol. A biphasic injection protocol is used for pulmonary or systemic arterial angiography, with image acquisition timed to opacification of the vessel of interest. The contrast medium is usually administered by using dual-­ head power injector at injection rate of 0.8–1 ml/ sec in neonates and young infants, 2  ml/sec in toddlers, and 4–5  ml/sec in teenagers or young adults [1, 4, 23]. An equal-sized bolus of saline flush infusion (sodium chloride solution) is injected at the same flow rate to reduce high-­ density contrast artifact (perivenous streak artifact). Automated bolus tracking technique with reference cardiovascular structure being monitored at near real time until predetermined threshold opacification of 100–150 Hounsfield units is achieved at a reference level for automated triggering or visual monitoring with manual triggering can be used. Scan delay of 4  seconds is commonly used to evaluate right-sided heart structures, and a scan delay of 5–8  seconds is used to evaluate left-sided heart structures. For patients with high heart rates, the operator may choose a slightly shorter triggering delay so that the acquisition is completed 2–3  seconds ahead of the contrast infusion, ensuring contrast delivery throughout the acquisition. For patients with intracardiac mixing, a longer and slower contrast injection with image acquisition at the end of injection often allows venous and arterial opacification on the same scan. It is very important to remember that for all acquisitions, injection protocols are tailored to the specific patient and exam conditions, by adjusting the injection rate, injection volume, and/or injection duration based upon the patient’s body weight, cardiac function, the scan distance, table speed, the acceptable noise, and the size of

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the peripheral venous catheter. The usual weight-­ based total contrast dose is 1.1 ml to 2 ml/kg of body weight. A biventricular injection protocol (a triphasic injection protocol) with two-phase contrast injection (pure contrast and diluted contrast with saline) followed by a saline flush is usually used for simultaneous pulmonary and aortic angiography. This method is very useful in patients after arterial switch operation, right ventricular-to-­ pulmonary artery conduit placement, or any lesion where simultaneous evaluation of leftsided and right-sided structures is needed. One method of achieving biventricular opacification is to give half the contrast at the usual arterial rate followed by diluted contrast (e.g., 50:50% mix) for the second phase of the contrast bolus and then followed by saline flush as third-phase injection. Delayed venous phase acquisition may be used after bidirectional Glenn or Fontan procedure or if there is any suspected systemic venous anomaly which needs further evaluation. Delayed venous phase scan can be obtained after 30–60  seconds of delay depending on the age, size, and heart rate of the patient.

D. A. Adebo

artery evaluation is needed. Prospective ECG-­ triggered technique with wider acquisition window (padding) can also be used for ventricular function assessment. For anatomic evaluation, prospective ECG-triggered technique is the preferred approach. Acquisition parameters are selected to maximize spatial and contrast resolution while minimizing noise and artifacts. The artifacts may include cardiac motion, respiratory motion, patient motion, high-density streaks, and beam hardening. Image noise will increase when reducing the detector width. Contrast resolution is directly dependent upon the degree of iodine attenuation and the tube voltage. For neonates and young infants, tube voltage of 70–80 KV is used with newer-generation multidetector scanners. For teenagers, 100–120 KV may be used depending on body size and presence or absence of internal objects causing metallic artifact. Reducing the voltage will increase iodine attenuation as the photons will be closer to the k-edge of iodine. Reducing the voltage will also yield less radiation dose [38]. Whether the voltage is dialed down to improve contrast resolution, reduce radiation exposure, or both, image noise will increase. In addition to decreasing the voltage, the other means to Cardiac CT Techniques increase iodine attenuation is to directly increase the iodine content in the targeted terriand Post-Processing tory. However, the amount of iodine that can be The newer-generation multidetector and dual-­ safely delivered is limited by a patient’s body source CT scanners provide fast scan with weight and renal function. increased anatomic coverage, low radiation dose, The operator can manipulate the tube current and acceptable noise. To optimize photon deliv- (mA) and exposure time (seconds) to control the ery and minimize the impact of noise, the patient flow of photons and radiation exposure (tube curis positioned with targeted region isocenter in the rent exposure time, mAs) to optimize image gantry. Removing surface metallic artifact objects quality. Low radiation exposure is also achieved yields uniform distribution of photons and by increasing the gantry rotation speed and the reduces streak artifact. Increasing the tube volt- pitch, as the scan time will decrease. However, age will decrease streak artifact from internal with newer multidetector CT technology, tube metallic objects. current is maintained at a constant level indepenFor pediatric cardiac CT, the upper extremities dent of the pitch and gantry speed. Maximizing are raised out of the field of view. This strategy table speed reduces the scan duration and exporeduces noise from increased soft tissue sure time and overall radiation exposure. When attenuation. adjusting either voltage or the tube current, the Retrospective ECG-gated acquisition is used operator should keep in mind that radio-­ when ventricular volume/function and coronary sensitivities are greatest for the neonate, followed

2  Techniques of Cardiac CT Scan: Patient Preparation, Contrast Medium, Scanning, and Post-Processing

subsequently by the infant, toddler, young child, and lastly the adolescent or adult. Automated tube current modulation software should be used in all pediatric cardiac CT angiograms to account for variable attenuation in the Z-axis. The exception may be the large body-­ habitus patient with suboptimal heart rate control. Pediatric cardiac CT scan starts by obtaining topogram (Fig. 2.1) which is used to prescribe the axial images. The topogram voltage should be set to equal the anticipated voltage for the actual cardiac CT acquisition to utilize automated tube current modulation. Non-contrast acquisition is rarely used in pediatric cardiac CT unless there is strong suspicion for coronary calcification from the clinical history or acute hemorrhage in post-trauma or postoperative patient. Contrast-enhanced angiographic images are obtained covering the region of interest in the chest to cover cardiac structures. Delayed post-contrast images are needed if there is any concern for systemic venous abnormality. Timing acquisition is not used in pediatric cardiac CT to avoid excess contrast dose. Pediatric cardiac CT scan triggering can be done using automatic bolus tracking technique or manual bolus tracking technique. Automatic bolus tracking technique is used when there is normal systemic and pulmonary venous drainage with minimal or no intracardiac shunting.

Fig. 2.1  A 16-year-old patient with suspected coronary artery anomaly. Topogram obtained to start pediatric cardiac CT scan

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Automatic triggering of the scan happens when the contrast reaches a pre-defined Hounsfield unit (HU) in a region of interest (ROI) placed in the structure of interest. This method does not require additional contrast use. The tube power and current can be decreased to reduce radiation exposure during the monitoring sequence. For right-sided structures, scan delay of 4 seconds is commonly used, and scan delay of 5–8 seconds is used for ­evaluation of left-sided structures [1, 4, 36, 37]. Manual bolus tracking can be used in patients with complex congenital heart disease where contrast timing is difficult to predict due to intracardiac shunting. Bolus tracking is used to manually trigger the scan after visualization of contrast in the area of interest on the monitoring sequence. The region of interest for monitoring is placed outside of the body, with the scan initiated manually from structures identified visually on the monitoring sequence. This approach may be the most reliable in patients with known venous occlusions and venous collateral vessels that will not fill in the normal time frame [39, 40]. Fixed time from injection triggering approach is imprecise due to the variability of contrast transit from different injection sites, contrast injection rate, collaterals, cardiac shunting, etc. Hence, the use of this method may lead to a non-­ diagnostic scan in the setting of systemic venous abnormality. Cardiac CT may be used to assess cannula position, presence of thrombus, or line infection in patients with extracorporeal membrane oxygenation (ECMO) or ventricular assist devices [41]. Conventional imaging at times may be challenging with this group of patients [42]. To prevent dilution of contrast medium in the ECMO system, contrast agent can be administered into the arterial ECMO tubing after the membrane oxygenator or into the venous line distal to the membrane oxygenator [43]. If possible, it is suggested to reduce pump flow after contrast medium is administrated. Peripheral contrast injection with the use of the cannulated limb is not recommended in patients on veno-arterial-ECMO due to insufficient circulation and venous return in the distal limbs.

D. A. Adebo

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a

c

b

d

Fig. 2.2  Neonate with tetralogy of Fallot, severe pulmonary stenosis, and unusual origin of patent ductus arteriosus as first arch vessel and supplying branch pulmonary

arteries. Axial image (a) and reformatted images in coronal (b) and sagittal views (c). Three-dimensional volume rendered reconstruction (d)

Once the scan is performed, images are reconstructed with slice thickness of 0.6  mm and an increment of 0.6  mm for cardiac evaluation. Iterative reconstruction is used to keep tube current low and minimize radiation exposure. Images are reformatted in coronal and sagittal views to review the anatomy and volume rendered reconstruction (Fig. 2.2). Two-dimensional multiplanar (MPR) and curved planar (CPR) reformations are most beneficial for analysis of structural detail, namely, cardiac morphology and vessel lumens and walls. Image analysis display and interpretation of pediatric cardiac CT angiograms are most efficient with the primary use of advanced workstation visualization techniques and secondary review of the source images. In all instances, it is essential to use flexible angiographic window and level settings, including a wide window setting to account for noise, vascular calcification, and high contrast attenuation. Regarding the

workflow, source data is acquired as two-­ dimensional (2D) transverse images and transferred to a picture archiving and communication system (PACS) for viewing and storage. Workstations are integrated into PACS or exist as separate systems (thin client servers or stand-­ alone units). Only thin section datasets (angiographic and non-contrast acquisitions) need transfer to the workstation. The size of datasets impacts transmission, display, and interpretation and depends upon the coverage, reconstruction interval, and the use and percentage of multiphase reconstructions. Three-dimensional volume rendered reconstruction and 2D maximum intensity projection (MIP) techniques provide angiographic overviews. Image editing may be needed to remove bones and other anatomic structures which may obscure vascular visualization. Source images are essential to assess image quality and exclude artifacts.

2  Techniques of Cardiac CT Scan: Patient Preparation, Contrast Medium, Scanning, and Post-Processing

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Image review may proceed with the original 8. Dillman JR, Hernandez RJ. Role of CT in the evaluation of congenital cardiovascular disease in children. transverse sections, the coronal and sagittal reforAJR Am J Roentgenol. 2009;192:1219–31. mations, or both. PACS review of non-­ 9. Siegel MJ.  Cardiac CTA: congenital heart disease. cardiovascular structures is facilitated by Pediatr Radiol. 2008;38(suppl 2):S200–4. generating 2-mm-thick axial reconstruction in 10. Achenbach S, Barkhausen J, Beer M, et al. Consensus recommendations of the German Radiology Society lung or bone window. Alternatively, coronal and (DRG), the German Cardiac Society (DGK) and the sagittal reformations may be used. Quantitative German Society for Pediatric Cardiology (DGPK) analysis of chamber volumes and ventricular on the use of cardiac imaging with computed tomography and magnetic resonance imaging. Rofo. ejection fractions can be analyzed using satellite 2012;184:345–68. workstation and multiplanar reformatting and 11. Nicol ED, Gatzoulis M, Padley SP, Rubens contouring technique (please see Chapter on M. Assessment of adult congenital heart disease with Cardiac Computed Tomography in evaluation of multi-detector computed tomography: beyond coronary lumenography. Clin Radiol. 2007;62:518–27. ventricular function).

References 1. Dodge-Khatami J, Adebo DA. Evaluation of complex congenital heart disease in infants using low dose cardiac computed tomography. Int J Cardiovasc Imaging. 2021. https://doi.org/10.1007/s10554-­020-­02118-­7. 2. Goo HW.  Cardiac MDCT in children: CT technology overview and interpretation. Radiol Clin N Am. 2011;49:997–1010. 3. Leschka S, Oechslin E, Husmann L, et  al. Preand postoperative evaluation of congenital heart disease in children and adults with 64-section CT. Radiographics. 2007;27:829–46. 4. Hellinger JC, Poon M, Epelman M.  Pediatric 64channel CT angiography: technical and clinical applications in 1550 consecutive examinations. JACC. 2010;55(16):A201. 5. Warnes CA, Williams RG, Bashore TM, et al. ACC/ AHA 2008 guidelines for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Develop Guidelines on the Management of Adults with Congenital Heart Disease). Developed in Collaboration with the American Society of Echocardiography, Heart Rhythm Society, International Society for Adult Congenital Heart Disease, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. J Am Coll Cardiol. 2008;52:143–263. 6. Khairy P, Van Hare GF, Balaji S, et  al. PACES/ HRS expert consensus statement on the recognition and management of arrhythmias in adult congenital heart disease: executive summary. Heart Rhythm. 2014;11:81–101. 7. Bhatt AB, Foster E, Kuehl K, et al. Congenital heart disease in the older adult: a scientific statement from the American Heart Association. Circulation. 2015;131:1884–931.

12. Huang MP, Liang CH, Zhao ZJ, et  al. Evaluation of image quality and radiation dose at prospective ECG-triggered axial 256-slice multi-detector CT in infants with congenital heart disease. Pediatr Radiol. 2011;41:858–66. 13. Ben Saad M, Rohnean A, Sigal-Cinqualbre A, Adler G, Paul JF. Evaluation of image quality and radiation dose of thoracic and coronary dual-source CT in 110 infants with congenital heart disease. Pediatr Radiol. 2009;39:668–76. 14. Al-Mousily F, Shifrin RY, Fricker FJ, Feranec N, Quinn NS, Chandran A.  Use of 320-detector computed tomographic angiography for infants and young children with congenital heart disease. Pediatr Cardiol. 2011;32:426–32. 15. Han BK, Overman DM, Grant K, et al. Non-sedated, free breathing cardiac CT for evaluation of complex congenital heart disease in neonates. J Cardiovasc Comput Tomogr. 2013;7:354–60. 16. Lell MM, May M, Deak P, et  al. High-pitch spiral computed tomography: effect on image quality and radiation dose in pediatric chest computed tomography. Investig Radiol. 2011;46:116–23. 17. Crean A.  Cardiovascular MR and CT in congenital heart disease. Heart. 2007;93:1637–47. 18. Jadhav SP, Golriz F, Atweh LA, Zhang W, Krishnamurthy R.  CT angiography of neonates and infants: comparison of radiation dose and image quality of target mode prospectively ECG-gated 320-­ MDCT and ungated helical 64-MDCT.  AJR Am J Roentgenol. 2015;204:W184–91. 19. National Kidney Foundation. K/DOQI clinical practice guidelines for vascular access, 2000. Am J Kidney Dis. 2001;37(Suppl 1):S137–81. 20. Li J, Udayasankar UK, Toth TL, Seamans J, Small WC, Kalra MK.  Automatic patient centering for MDCT: effect on radiation dose. AJR Am J Roentgenol. 2007;188:547e552. 21. Kuo F, Plaza M, Saigal G.  Inappropriate arm positioning during scout image acquisition resulting in increased radiation dose while performing a chest CT. Pediatr Radiol. 2012;42:508–9. 22. Vastel-Amzallag C, Le Bret E, Paul JF, et  al. Diagnostic accuracy of dual-source multislice com-

22 puted tomographic analysis for the preoperative detection of coronary artery anomalies in 100 patients with tetralogy of Fallot. J Thorac Cardiovasc Surg. 2011;142:120–6. 23. Amaral JG, Traubici J, BenDavid G, Reintamm G, Daneman A. Safety of power injector use in children as measured by incidence of extravasation. AJR Am J Roentgenol. 2006;187:580–3. 24. Plumb AA, Murphy G.  The use of central venous catheters for intravenous contrast injection for CT examinations. Br J Radiol. 2011;84:197–203. 25. Rigsby CK, Gasber E, Seshadri R, Sullivan C, Wyers M, Ben-Ami T. Safety and efficacy of pressure-limited power injection of iodinated contrast medium through central lines in children. AJR Am J Roentgenol. 2007;188:726–32. 26. Blass EM, Hoffmeyer LB. Sucrose as an analgesic for newborn infants. Pediatrics. 1991;87:215–8. 27. Mahabadi AA, Achenbach S, Burgstahler C, et  al. Safety, efficacy, and indications of beta-adrenergic receptor blockade to reduce heart rate prior to coronary CT angiography. Radiology. 2010;257:614–23. 28. Dewey M, Vavere AL, Arbab-Zadeh A, et al. Patient characteristics as predictors of image quality and diagnostic accuracy of MDCT compared with conventional coronary angiography for detecting coronary artery stenoses: CORE-64 Multicenter International Trial. AJR Am J Roentgenol. 2010;194:93–102. 29. Roberts WT, Wright AR, Timmis JB, Timmis AD. Safety and efficacy of a rate control protocol for cardiac CT. Br J Radiol. 2009;82:267–71. 30. Hausleiter J, Meyer T, Hermann F, et  al. Estimated radiation dose associated with cardiac CT angiography. JAMA. 2009;301:500–7. 31. Goldstein JA, Chinnaiyan KM, Abidov A, et al. The CT-STAT (coronary computed tomographic angiography for systematic triage of acute chest pain patients to treatment) trial. J Am Coll Cardiol. 2011;58:1414–22. 32. Rigsby CK, de Freitas RA, Nicholas AC, et al. Safety and efficacy of a drug regimen to control heart rate during 64-slice ECG-gated coronary CTA in children. Pediatr Radiol. 2010;40:1880–9. 33. Taylor AJ, Cerqueira M, Hodgson JM, et  al. ACCF/ SCCT/ACR/AHA/ASE/ASNC/ NASCI/SCAI/ SCMR 2010 Appropriate Use Criteria for Cardiac Computed Tomography. A Report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the Society of Cardiovascular Computed Tomography, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the American Society of Nuclear Cardiology, the North American

D. A. Adebo Society for Cardiovascular Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society for Cardiovascular Magnetic Resonance. J Cardiovasc Comput Tomogr. 2010;4:1–33. 34. Decramer I, Vanhoenacker PK, Sarno G, et al. Effects of sublingual nitroglycerin on coronary lumen diameter and number of visualized septal branches on 64- MDCT angiography. AJR Am J Roentgenol. 2008;190:219–25. 35. Hussein AA, Abutaleb A, Jeudy J, et  al. Safety of computed tomography in patients with cardiac rhythm management devices: assessment of the U.S.  Food and Drug Administration advisory in clinical practice. J Am Coll Cardiol. 2014;63:1769–75. 36. Fleischmann D, Rubin GD. Quantification of intravenously administered contrast medium transit through the peripheral arteries: implications for CT angiography. Radiology. 2005;236(3):1076–82. 37. Lee CH, Goo JM, Bae KT, et  al. CTA contrast enhancement of the aorta and pulmonary artery: the effect of saline chase injected at two different rates in a canine experimental model. Investig Radiol. 2007;42(7):487–90. 38. Huda W, Ogden KM, Khorasani MR. Converting dose-­ length product to effective dose at CT.  Radiology. 2008;248(3):995–1003. 39. Han BK, Rigsby CK, Leispic J, et  al. Computed tomography imaging in patients with congenital heart disease, part 2: technical recommendations. An expert consensus document of the Society of Cardiovascular Computed Tomography (SCCT). J Cardiovasc Comput Tomogr. 2015;9:493–513. 40. Han BK, Rigsby CK, Hiavacek A, et  al. Computed tomography imaging in patients with congenital heart disease part I: rationale and utility. An expert consensus document of the Society of Cardiovascular Computed Tomography (SCCT). J Cardiovasc Comput Tomogr. 2015;9:475–92. 41. Friedman BA, Schoepf UJ, Bastarrika GA, Hlavacek AM.  Computed tomographic angiography of infants with congenital heart disease receiving extracorporeal membrane oxygenation. Pediatr Cardiol. 2009;30:1154–6. 42. Acharya D, Singh S, Tallaj JA, et  al. Use of gated cardiac computed tomography angiography in the assessment of left ventricular assist device dysfunction. ASAIO J. 2011;57:32–7. 43. Lidegran MK, Ringertz HG, Frenckner BP, Lindén VB.  Chest and abdominal CT during extracorporeal membrane oxygenation: clinical benefits in diagnosis and treatment. Acad Radiol. 2005;12:276–85.

3

Evaluation of Cardiac Malposition, Cardiac Segmental Approach, and Heterotaxy Syndrome Mehul D. Patel

Introduction Evaluation of congenital heart defects can be challenging due to the wide variety of possible defects, their anatomic location, and physiologic effects or severity. This is most evident in evaluation of patients with multiple cardiac defects or those with abnormal organ laterality (such as heterotaxy syndrome). A comprehensive, systematic categorization scheme is helpful for the diagnosing physician in several ways: to categorize patients and their constellation of defects into broad categories (and gain insight into the shared embryologic developmental anomalies leading to these defects), to evaluate the components and potential abnormalities of cardiac anatomy, and then to communicate these abnormalities in a succinct yet complete manner to the multidisciplinary teams and specialists involved in these patients’ care. Cardiac CT offers many advantages in the evaluation of pediatric patients with complex congenital defects and abnormal cardiac relationships including rapid imaging times with high resolution and level of detail, allowing evaluation of abnormal systemic or pulmonary M. D. Patel (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

venous connections, abnormal airway anatomy [1], and visualizing proximal and distal branches of the pulmonary arteries and aorta. Throughout the modern era of the study of congenital heart disease, multiple naming systems have been proposed [2–5] with a select group gaining popularity; this has also led to multiple redundant terminologies which can be confusing for the trainee or experienced clinician alike. In this chapter we aim to describe the overall approach used by most of these systems (termed “the segmental approach” [3, 5] or “sequential segmental analysis” [4]) and will describe the broad classification schemes by referring to terms and descriptions from the system outlined by the International Society for Nomenclature of Paediatric and Congenital Heart Disease [6] and refer to other naming systems when relevant. Regardless of the system or terminology favored by the diagnostic physician, she or he should aim to describe each major aspect of segmental anatomy in a clear and complete manner. The basic components of cardiac position and segmental anatomy that should be evaluated, when possible, in each exam include cardiac position, pulmonary and abdominal (visceral) situs, systemic and pulmonary venous connections, atrial situs, ventricular situs and atrioventricular relationships, outflow tracts and ventriculoarterial connections, and the great arteries. We will describe classification and

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_3

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n­ aming schema for each of the segmental anatomy components and focus on specific examples and imaging scenarios for complex cases such as those with heterotaxy syndrome.

Cardiac Position The heart’s position is defined by which hemithorax mainly resides in: levocardia is normal with the heart positioned in the left hemithorax with the cardiac apex pointing leftward, dextrocardia when the heart is positioned in the right hemothorax and apex pointing rightward (Fig. 3.1a), and mesocardia when the heart resides between either the hemithorax and the apex pointing anteriorly or midline [5]. Abnormal cardiac position is often found in isolation of other defects of laterality but may be associated with heterotaxy syndrome [7] or situs inversus totalis. Dextroposition is when the heart resides within the right hemithorax but with the cardiac apex pointing leftward (normal). This is often associated with other anatomic defects which can displace the heart and mediastinal structures rightward, such as a left congenital diaphragmatic hernia [8] or right lung hypoplasia [7].

Pulmonary and Abdominal (Visceral) Situs Congenital abnormalities in pulmonary and abdominal organs can be associated with congenital heart defects, most often in the setting of heterotaxy syndrome. The Greek root words heteros (meaning other) and taxis (meaning arrangement) describe the defining features of this syndrome well: abnormal lateralization of the thoracic and abdominal organs (such as the heart, lungs, airways, stomach, liver, spleen) that lack their normal asymmetric locations and relationships [7]. As mentioned above, others may coexist with congenital heart defects such as congenital diaphragmatic hernia, airway abnormalities, etc. Therefore, evaluation of the position and relationships of the above organs is

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critical, especially if associated syndromes or defects are suspected. The right and left lungs are inherently asymmetric, with the right lung typically formed of three major lobes with the right mainstem bronchus positioned eparterial (or just superior) to the corresponding right pulmonary artery [8]. The left lung is typically formed of two major lobes with a hyparterial left mainstem bronchus (positioned just inferior of the left pulmonary artery). Laterality or presence of these bronchopulmonary patterns may be abnormal in heterotaxy syndrome, and patients may have findings of bilateral morphologic right or left bronchopulmonary patterns (Fig.  3.2b). Patients may also have morphologic right and left bronchopulmonary patterns in mirror image, such as in situs inversus totalis. Bronchopulmonary morphology may be evaluated by examination of the lobes and fissures (such as in sagittal views), but morphologic evaluation of the mainstem bronchi can quickly aid definition. This is best done in multiplanar reformats of the trachea and major airways in an oblique coronal plane, as shown in the associated figures. Depending on the field of view chosen, abdominal organs may be included in diagnostic imaging data. If infradiaphragmatic abnormalities of the pulmonary veins or systemic veins are suspected (which is not uncommon in heterotaxy syndrome), the field of view should be set larger as mentioned below to evaluate the abnormal venous connections. The visceral situs or abdominal organ relationship should be evaluated by first defining the position of the liver, stomach, and spleen. Prior to the cardiac CT examination, review of the patient’s radiograph can give initial clues to abnormal position of the liver or stomach. Visceral Situs Solitus  The liver is normally positioned rightward with the left lobe just crossing midline, stomach positioned leftward and anterior, and the spleen leftward and posterior which is termed abdominal (or visceral) situs solitus. If the organs are positioned abnormally in a mirror-imaged arrangement, this is termed

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Fig. 3.1 (a) A 4-year-old girl with atrial situs inversus, atrioventricular discordance with D-looped ventricles, and ventriculoarterial discordance with D-transposition of the great arteries. In Van Praagh segmental approach, this anatomy would be classified as {I, D, D} segmental anatomy. This patient underwent main pulmonary artery band placement. (a) Axial image at the level of the mid-atria, showing dextrocardia with rightward cardiac apex. The RV is heavily trabeculated with a more apically displaced tricuspid valve septal leaflet and is posterior and slightly more rightward than the LV. Using the hand rule, we can imagine the patient’s right hand in the RV (as described above), confirming the diagnosis of D-looped ventricles. RV, right ventricle; LV, left ventricle. (b) Axial image at the level of the upper abdomen, showing abdominal situs inversus with the liver, stomach (S), and spleen (SP) in mirror-imaged arrangement. (c) Oblique axial reformat of the right (RA) and left atria (LA), demonstrating exten-

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sion of pectinate muscle throughout the left-sided RA, in contrast to the right-sided LA which has pectinate muscles confined to the narrow LA appendage (LAA). This confirms the diagnosis of atrial situs inversus. (d) Oblique sagittal reformat in short axis plane of the ventricles, showing a dilated and hypertrophied RV which is the systemic ventricle in this defect, in contrast to the subpulmonary LV which is thinner and not dilated. Combined with the other images, we can determine there is atrioventricular and ventriculoarterial discordance and describe the segmental anatomy. RV, right ventricle; LV, left ventricle. (e) Oblique axial reformatted image at the level of the aortic (Ao) and pulmonary artery (PA) roots. The aorta arises from the systemic RV and is located side by side and rightward of the pulmonary valve, confirming the diagnosis of D-transposition of the great arteries. The pulmonary artery arises from the LV, and the narrowing from the MPA band (B) is also seen

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when abnormal should be described as visualized. Bronchopulmonary morphology should be described as normal, bronchopulmonary mirror image (or inversus), right isomerism, left isomerism, or undetermined. Abdominal situs should be described as abdominal situs solitus (normal), abdominal situs inversus, abdominal situs ambiguus (with position of the liver and stomach described, as well as presence, absence, or number of spleen organs), or undetermined.

Systemic Venous Connections Fig. 3.1 (continued)

abdominal situs inversus (Fig.  3.1b). If the organs are positioned abnormally, but not in a complete mirror-imaged arrangement (such as a midline liver, stomach, and liver either present on same side, absent, or multiple spleen structures), this is termed abdominal situs ambiguous [5] (Fig.  3.2a). Abdominal situs ambiguus is often associated with functional abnormalities of the spleen, malrotation of the gut, or more rarely biliary atresia [7]. Abnormal position of the liver is often associated with abnormalities of systemic venous anatomy as discussed below. Some investigators and nomenclature systems initially classified heterotaxy syndrome patients in broad categories based on splenic anatomy: asplenia syndrome [9] with bilateral right atrial appendages, right bronchopulmonary pattern, complete atrioventricular septal defect, and pulmonary stenosis or atresia and and polysplenia syndrome [10] with bilateral left atrial appendages, left bronchopulmonary pattern, interrupted inferior vena cava, and dextrocardia. However, we discourage using this dated nomenclature system, as these associations are sometimes found together but more typically have exceptions and variations [11] and not helpful in predicting the associated defects. Therefore, in summary, the bronchopulmonary patterns and abdominal organs (liver, stomach, spleen) should be evaluated in terms of relative position and their normal asymmetry and

Variants of systemic venous connections are often found in patients with congenital heart disease, both with and without heterotaxy syndrome. These are described in further detail in Chap. 4 of this textbook (Anomalous Systemic Venous Connections). In brief, the most common systemic venous abnormality is a persistent left superior vena cava (SVC). An innominate vein that “bridges” the right- and left-sided SVCs may or may not be present and should be evaluated if adequately visualized. Other variants found include a left SVC with atretic right SVC or biatrial drainage of the right SVC [12]. Systemic venous abnormalities are frequent in heterotaxy syndrome, and their laterality or position can vary. One major abnormality is interrupted inferior vena cava (IVC), which is sometimes (but not always, as mentioned above) associated with the presence of bilateral left atrial appendages. Inferior body venous drainage in this defect continues through the common azygos trunk (typically visualized anterior to the vertebral column but may be positioned rightward or leftward) through the abdomen, into the thorax, and then arches anteriorly into the (either right or left-sided) SVC. There may be bilateral superior vena cavae in association. The hepatic veins continue to connect to the atria, but as described below, their position and number of connections can vary. Hepatic venous drainage is also frequently variable in heterotaxy syndrome; the hepatic veins drain to the floor of the atria, but they can connect to the right-sided or left-sided atrium or

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Fig. 3.2  A 1-month-old neonate with heterotaxy syndrome, abdominal situs ambiguus (with asplenia), aorta arising from RV, pulmonary atresia, and mixed total anomalous pulmonary venous connection (TAPVC). (a) Axial image just inferior of diaphragm showing midline liver mass, right-sided gastroesophageal junction (S, note enteric feeding tube coursing toward right-sided stomach) demonstrating abdominal situs ambiguus. The large, dilated vessel at midline is the descending vertical vein (V) draining the mixed TAPVC. (b) Oblique coronal

reformat showing symmetric bronchi with bilateral morphologic right bronchopulmonary pattern (arrows). (c) Posterior view of three-dimensional volume rendered reconstruction showing the mixed TAPVC; the left upper (LU), right lower (RL), and right upper (RU) pulmonary veins drain into a common confluence which drains to the right-sided SVC (*). A decompressing vein also connects to the left lower (LL) pulmonary vein which drains inferiorly to the descending vertical vein (V), note the dilated collecting vein inferiorly in the liver

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Fig. 3.3 A 2-week-old neonate with heterotaxy syndrome, abdominal situs ambiguus, atrial situs ambiguus (with isomerism of right atrial appendages), D-looped ventricles, double-outlet RV with normally related great arteries, hypoplastic LV, and supracardiac total anomalous pulmonary venous connection (TAPVC). (a) Oblique coronal maximum intensity projection reformat showing multiple systemic venous anomalies including a right-­ sided IVC and hepatic veins (RV) draining to the right-­ sided atrium, left-sided hepatic veins (LV) draining

separately to the left-sided atrium, and bilateral SVCs with a left-sided (LS) and right-sided (RS) SVC draining to their respective atria. A central venous catheter is seen within the right SVC. (b) Oblique coronal maximum intensity projection reformat at the base of the heart showing isomerism of the right atrial appendages. Both right-­ sided and left-sided appendages have a broad base, large pyramidal shape, and coarse pectinate muscles which extend out of the appendage. RAA right-sided atrial appendage, LAA left-sided atrial appendage

both (Fig. 3.3a), depending on the position of the liver relative to the atria. All hepatic veins may variably drain to the suprahepatic IVC (when present) or drain separately to a common central area or drain at separate left and right-sided points. The inferior vena cava can also variably be present on the right or left side and usually connects to the morphologic right atrium. Given this wide heterogeneity, abnormal venous connections are most accurately described when reported individually. Cardiac CT examination preparation should focus on structures that were not fully or completely evaluated by other modalities such as echocardiography, but a single acquisition (or additional second acquisition) in a delayed venous phase can often outline abnormal systemic venous connections as well as the great arteries and intracardiac structures. An alternative approach is to plan contrast injection through the venous channel in question to demonstrate patency; for example, contrast injection through a leg peripheral IV in a case of interrupted IVC will show, with an early arterial phase acquisition, enhancement along the dilated azygos vein, and its drainage to a superior vena cava. To avoid beam-hardening artifact from dense contrast, we

recommend dilution of contrast (e.g., 70–80% contrast with 20–30% saline) or a triphasic injection technique (66–75% contrast given initially, followed by 25–33% contrast mixed in 50:50 ratio with saline, followed by saline flush). These abnormalities may be relevant for pre-surgical planning if the planned cardiac operation includes systemic venous diversion or baffling, such with a cavopulmonary (Fontan) procedure, atrial baffle (Senning or Mustard operation), or atrial septation (atrial septal defect closure).

Pulmonary Venous Connections Similar to the wide variability in systemic venous abnormalities, there are a wide variety of abnormal pulmonary venous connections. These are described in further detail in Chap. 5 of this textbook (Anomalous Pulmonary Venous Connections). Anomalous pulmonary venous connections can be found in isolation or in association with a variety of congenital heart defects but occur frequently with heterotaxy syndrome (particularly in those with the presence of bilateral right atrial appendages). Total anomalous

3  Evaluation of Cardiac Malposition, Cardiac Segmental Approach, and Heterotaxy Syndrome

pulmonary venous connections (TAPVC) occur in approximately two-thirds of patients with heterotaxy syndrome and bilateral right atrial appendages, and any form of partial or total anomalous pulmonary venous connection should be strongly suspected in all cases of heterotaxy syndrome. If infracardiac (infradiaphragmatic) TAPVC is suspected, the scan field of view should be extended down to image most of the liver, as the inferiorly draining vertical vein can extend far down through the liver itself (Fig. 3.2c). Alternatively, if supracardiac TAPVC is suspected, the field of view should extend upward through the innominate vein (or superior SVC) to completely evaluate ascending vertical vein drainage; for mixed TAPVC, the field of view may need to be extended both superiorly and inferiorly (Fig.  3.2c). Timing acquisition with adequate enhancement of the left heart and descending aorta usually allows good contrast perfusion and enhancement of the pulmonary veins; however in obstructed TAPVC, a longer delay before acquisition (similar to a typical venous phase) may be needed to allow adequate contrast to flow to the obstructed pulmonary veins.

Atrial Arrangement or Situs The atria are the first major, unique “building block” of intracardiac segmental anatomy. The right and left atria are the receiving chambers for systemic and pulmonary venous drainage, but in cases of complex congenital heart disease such as those with heterotaxy syndrome, the venous connections to the atria cannot be relied on to identify the morphologic identity of the atria. Although the IVC and coronary sinus usually connect to the morphologic right atrium [8], cases where the IVC connects to atria with isomerism of the left atrial appendages (based on examination of the appendages as described below) have been described [13]; as it is typical of heterotaxy syndrome, there are always exceptions! Uemura and Anderson [13] proposed classification of atrial anatomy based on the anatomic

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features within the atria – specifically the atrial appendages. The right atrial (RA) appendage has a broad base, triangular shape, and positioned more anteriorly [5] (Fig. 3.4a), while the left atrial (LA) appendage has a narrower base with a long and narrow (finger-like) shape and positioned more posterior in normal segmental anatomy (Fig. 3.4b). These aspects can be identified in most cases on tomographic imaging such as cardiac CT and may be better defined if cardiac motion is reduced with careful ECG gating or slower heart rates. A more defining feature of atrial anatomy evaluates the pectinate muscles; these are coarse and extend from the right atrial appendage to the central cardiac crux [13] (and atrioventricular valve) in the morphologic right atrium but are confined to the appendage in the morphologic left atrium. Unfortunately, the extent of atrial pectinate muscles may not be well visualized on cardiac CT depending on cardiac motion and was originally described based on autopsy specimen analysis. Additionally, the morphologic right atrium develops the superior limbus of the fossa ovalis, while the left atrium develops the septum primum which forms the valve of foramen ovale; however, the atrial septum may be nearly absent or not well developed in patients with heterotaxy syndrome, adding difficulty to classifying these cases. Therefore, we suggest classification of atrial situs and anatomy as advocated by the International Society for Nomenclature of Paediatric and Congenital Heart Disease [6], which is based on describing the atrial appendages. In the classification system proposed by Van Praagh [5], the alternate term and letter designation ({atrial, ventricular, great artery}) will also be given. Patients with usual atrial arrangement (also termed atrial situs solitus: S) have normal atrial position: the right atrial appendage on the right and left atrial appendage on the left. Mirror-imaged atria (or atrial situs inversus: I) have the right atrial appendage on the left and left atrial appendage on the right (Fig.  3.1c). When there are symmetric morphologic right atrial appendages, these patients have isomerism of the right atrial appendages (Fig.  3.3b).

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Fig. 3.4  A 13-year-old boy with normal segmental anatomy and ascending aorta dilation. (a) Oblique sagittal reformat of the right atrium, showing a normal size right atrium and its appendage (RAA), which has a broad base, anterior position, and coarse pectinate muscles which extend out of the atrial appendage along the inferior right atrial walls. Negative contrast swirling from non-­opacified

blood streaming from the inferior vena cava is also seen. (b) Oblique coronal reformat in the two-chamber LV plane, showing a normal-size left atrium and its appendage (LAA), which has a narrow base, long and finger-like shape, and pectinate muscles confined to the appendage. LV left ventricle

Similarly, when there are symmetric morphologic left atrial appendages, these patients have isomerism of the left atrial appendages. It should be noted that, due to occasional difficulties in defining appendage morphology as mentioned above, definitive evaluation is not always possible, and these patients should be classified as undetermined. In the Van Praagh classification system, isomerism of the right or left atrial appendages are broadly c­ lassified as atrial situs ambiguus (A), and if undetermined, classified as unknown (X). Some [6] attempt to broadly group abnormal laterality of the thoracic and abdominal organs with isomerism of the right or left atrial appendages (similar to the attempts to broadly define asplenia or polysplenia syndromes as mentioned above); however, in our experience we have found as many exceptions as examples to these classifications [11] and recommend defining atrial arrangement or situs in each case as a separate component rather than the basis for a broad class.

 entricular Situs and Atrioventricular V Relationships The ventricles are the second major intracardiac component of segmental anatomy, and differentiating the right and left ventricles is the next step. The right ventricle (RV) is normally positioned anteriorly with the right atrium, is asymmetric and trapezoidal in shape, has coarse trabeculations, and has distinct septal and moderator bands on the septum. Its atrioventricular (tricuspid) valve has chordal attachments normally to the septum [5], and its septal leaflet is more apically displaced when compared to the mitral valve leaflets (Fig. 3.5a). It is composed of three portions (inlet, apical trabecular, and outlet) with the outlet composed of the infundibulum (or conus), with muscular separation of the pulmonary valve and fibrous skeleton of the tricuspid-aortic-mitral valve. In contrast, the left ventricle (LV) is a symmetric structure (prolate ellipsoid), normally positioned posteriorly with the left atrium, and

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Fig. 3.5  A 2-day-old neonate with D-transposition of the great arteries, intact ventricular septum, and small atrial septal defect requiring balloon atrial septostomy. (a) Oblique axial reformat in the four-chamber plane demonstrating levocardia with D-looped ventricles (note the heavily trabeculated RV and smooth-walled LV). (b) Oblique sagittal reformat in the plane of the LVOT and RVOT outflow tracts demonstrating ventriculoarterial discordance, with the anterior aorta (Ao) arising from the RV and the main pulmonary artery (PA) arising from the

smooth-walled LV. There is also a large patent ductus arteriosus connecting both great arteries (PDA). (c) Oblique axial reformat at the level of the aortic (Ao) and pulmonary artery (PA) roots. The aorta is anterior and rightward of the pulmonary artery, gives rise to right- and left-sided coronary artery origins (*), and arises from the RV. This confirms the diagnosis of D-transposition of the great arteries. Also note the normal-appearing right (RAA) and left atrial appendages (LAA), also confirming atrial situs solitus

has fine smooth trabeculations (Fig.  3.5a). Its atrioventricular (mitral) valve has chordal attachments to 1–2 distinct papillary muscles on the LV free wall. Its outflow and aortic valve have fibrous continuity to the mitral valve, with no infundibulum separating it. In normal segmental anatomy, the above list of features helps differentiate the two ventricles; however, there can be wide ­variation in the position, atrioventricular

relationships, size, wall thickness, and ventriculoarterial (outflow tract) relationships which can confound classification of the ventricles. When other features of ventricular anatomy are not present or altered, the septal surface and features of the ventricles (coarse with septal and moderator bands in the RV, smooth superior septum in the LV) can be the most reliable feature [4, 5] (Figs. 3.1d and 3.6a).

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a

b

Fig. 3.6 A 1-week-old neonate with heterotaxy syndrome, abdominal situs ambiguus (with asplenia), atrial situs ambiguus, indeterminate ventricular looping, double-­outlet RV with A-malposed great arteries, common AV valve, and infracardiac total anomalous pulmonary venous connection (TAPVC). (a) Axial image showing a single functional ventricle (RV) with no identifiable second ventricular chamber. Given the heavy trabeculations, this is most likely a morphologic right

ventricle, but morphologic diagnosis is difficult and may be uncertain in cases such as these. A common atrioventricular valve is also seen. Also note the pulmonary venous confluence posterior to the left-sided atrium (*). (b) Axial image at the level of the aortic (Ao) and pulmonary artery (MPA) roots. The aorta is anterior and to the right of the pulmonary artery, with both great arteries arising from the right ventricle (RV). This confirms a diagnosis of double-­ outlet RV with dextro-malposed great arteries

Once the ventricles are identified as right versus left, then the ventricular relationships to the patient’s laterality can be defined. Ventricular anatomy has inherent chirality, and ventricular relationships are clinically relevant in predicting coronary artery distribution pattern, cardiac conduction system location, and risk of spontaneous atrioventricular block [5]. The ventricular position cannot be simply labeled as “right-sided” or “left-sided,” as the ventricles may be oriented in a relative anterior-posterior or superior-inferior relationship (such as in criss-cross atrioventricular connections). Therefore, the type of ventricular topology (or in Van Praagh classification, ventricular looping) is determined using another chiral structure: the hand. In right-hand ventricular topology (or D-looped ventricles), the right hand is imagined to be placed in the RV with the thumb in the tricuspid valve, with the palmar surface facing the ventricular septum and the dorsal surface facing the RV free wall – this is normal ventricular topology (Figs.  3.1a and 3.5a). Alternatively, in left-hand ventricular topology (or L-looped ventricles), the left hand is imag-

ined in the RV with the thumb in the tricuspid valve; the palmar surface will face the ventricular septum, and the dorsal surface will face the RV free wall [5]. Very rarely, if ventricular topology or looping cannot be determined, it should be labeled as undetermined (or unknown: X). In addition to this spatial description, the relative sizes or dominance of the ventricles should also be described, as one ventricle may be hypoplastic in size which will affect subsequent palliative surgical planning. The atrioventricular connections can vary in number and spatial relation and should also be described. One aspect is atrioventricular (AV) concordance; this is if the morphologic RA connects correspondingly to the morphologic RV (and similarly for the morphologic LA and LV). If the morphologic RA instead connects to the LV (such as with usual atrial arrangement and left-­ hand ventricular topology, as one example), this is AV discordance (Fig. 3.1a). The tricuspid valve originates from and connects to the RV, as the mitral valve does with the LV. Depending on the spatial relative relationships of the AV connec-

3  Evaluation of Cardiac Malposition, Cardiac Segmental Approach, and Heterotaxy Syndrome

tions and valves, it may be helpful to describe each as right-left, anterior-posterior, or superior-­ inferior of each other. Another aspect of atrioventricular connections is the number of connections and valves; in heterotaxy syndrome it can be common for a single common AV valve (Fig. 3.6a) to be present (such as with a complete AV septal defect) which may be equally balanced over both the right and left ventricles or unbalanced and primarily committed to a more dominant ventricle. If one AV valve is atretic (such as with tricuspid or mitral atresia), this should also be described. Two separate AV valves may not be perfectly aligned over their respective ventricles; for example, the tricuspid or mitral valve may override the ventricular septum and connect to both ventricles on either side of the septum [4]. The tricuspid or mitral valve may also straddle the ventricular septum and connect to both septal surfaces, or an AV valve may both straddle and override. Another separate type of AV connection is double-inlet ventricle; this occurs with two separate AV valves that both (completely or mostly) connect to a dominant ventricle (usually morphologic LV; however, cases of double-inlet RV have been described [14]).

33

Alternatively, both great arteries may arise primary from one ventricle; this is termed double-­ outlet ventricle. A full discussion of the spectrum of these anomalies and their morphologic analysis is beyond the scope of this chapter, and the interested reader should refer to the references for further reading [15]. Most often this presents as double-outlet right ventricle, with both great arteries arising mainly from the RV with an associated ventricular septal defect (Fig.  3.6b), and this is a frequent diagnosis in heterotaxy syndrome patients [7]. Normally there is a subpulmonary infundibulum (or conus) which appears as a cylindrical tube of the myocardium [15] connected to the RV, positioning the pulmonary artery anterior, leftward, and superior to the aorta. The aorta, in contrast, normally has little to no subaortic infundibulum with the aortic valve in fibrous continuity with the mitral valve. In congenital defects associated with abnormal VA alignments such as double-outlet RV, transposition of the great arteries, etc., each of the great arteries may or may not have an associated infundibulum (of varying sizes or obstruction) and may be positioned over the LV, ventricular septum, or RV.  The result of this variability is the broad spectrum of defects in double-outlet RV, transposition of the great arteries, tetralogy of Outflow Tracts and Ventriculoarterial Fallot, etc. Therefore, the presence of subaortic Alignments or subpulmonary infundibulum (or conus), degree of outflow obstruction, and position of the The paths of the outflow tracts can vary in loca- great arteries should be described. tion, may or may not be associated with an infunThe great arteries and outflow tracts can be dibulum (or conus), and may have varying spatially described in several ways; most comdegrees of obstruction. These are the key compo- monly the aortic valve position is described in nents that should be described. Similar to AV relation to the pulmonary valve. Note that these connections, one aspect is ventriculoarterial (VA) descriptors (below) only describe the great arterconcordance: this is if the morphologic RV con- ies in relation to each other and NOT their relanects correspondingly to the pulmonary artery tion to the ventricles (VA alignment). For (and similarly for the morphologic LV and aorta). example, a patient may have normally related If the morphologic RV instead connects to the great arteries and still have double-outlet RV, and aorta (such as with right-hand ventricular topol- therefore additional description is needed. If the ogy and D-transposition of the great arteries, as great arteries each arise from a morphologic disone example), this is VA discordance (Fig. 3.5b). cordant ventricle (with VA discordance as Transposition of the great arteries, as a stand-­ described above), then this should be described alone diagnosis, should be reserved for situations as D-transposition/l-transposition of the great of VA discordance, with each ventricle connected arteries as listed above, with transposition to its discordant great artery. reserved for one ventricle aligned with only one

M. D. Patel

34

great artery. If both great arteries arise from a ventricle, the defect should be described as double-­outlet (right or left) ventricle to differentiate it, and the great arteries described as d-malposed/l-malposed/a-malposed, etc. Normally, as described above, the aortic valve is posterior, rightward, and inferior of the ­pulmonary valve; this term is normally related to great arteries (or in Van Praagh classification, arterial situs solitus (S) in the third letter designation). If the aortic valve is rightward (may also be anterior) of the pulmonary artery, this is d-­malposed (Fig. 3.6b) or d-transposed (if there is VA discordance as described above), termed D (Figs. 3.1e and 3.5c). If the aorta is leftward (may also be anterior), this is l-malposed (or l-­transposed), termed L. If the aorta is positioned directly anterior to the pulmonary valve (and neither rightward nor leftward), this may be termed anterior-malposed (or anterior-transposed), termed A. If one great artery is atretic or unidentifiable (e.g., as may happen not infrequently in heterotaxy syndrome, with pulmonary atresia [7]), then this is termed X or undetermined. This classification also applies to patients with only one developed great arterial trunk, such as with truncus arteriosus. These spatial relations can be usually determined clearly in the axial plane, assuming the patient is positioned flat, supine, and aligned. As mentioned above, the subaortic or subpulmonary infundibulum (or conus) may have varying degrees of regression, thickening, or obstruction especially in patients with defects of VA alignment. For example, patients with tetralogy of Fallot may have multi-level pulmonary outflow obstruction from subvalvar infundibular thickening or hypoplasia, in addition to valvar and supravalvar stenosis. The infundibular myocardium can be visualized on CT and appear as a knob of muscle positioned subvalvar, which may be of varying size. There may be separation of the normal fibrous continuity of the mitral and aortic valves [15]. This may cause subvalvar obstruction; however, this may or may not be apparent on cardiac CT depending on the degree of obstruction and hemodynamic loading conditions and may be better evaluated on echocar-

diography with Doppler evaluation. Therefore, the presence of subaortic or subpulmonary infundibulum should be described, and the presence of subvalvar infundibular muscle or obstruction should be described, but assessing the degree of obstruction may not be accurate on static cardiac CT images. These structures are best seen on multiplanar reformats through the outflow tracts and infundibulum and may (or may not) be seen in straight sagittal planes.

The Great Arteries Evaluation of the great arteries is a common indication for cardiac CT in patients with complex congenital heart defects and/or heterotaxy syndrome and can provide a wealth of information. The pulmonary arteries may be hypoplastic, atretic, or discontinuous. The main and branch pulmonary arteries should be described in terms of size, focal narrowing, or stenosis and measured at abnormal areas in orthogonal planes. As mentioned above, patients with heterotaxy syndrome may have pulmonary stenosis or atresia, and some may have differing sources of pulmonary blood flow. For example, the main pulmonary artery may be atretic with separate right and left pulmonary arteries in discontinuity, with blood flow supplied by separate aortopulmonary connections (such as a patent ductus arteriosus (PDA) or aortopulmonary collateral artery). In heterotaxy syndrome in particular, patients may have a right-sided or bilateral PDA, and this should be suspected in patients with what may appear as major aortopulmonary vessels. Depending on timing of diagnosis or clinical management, the PDA may be large (Fig. 3.5b), medium, or small, and it should be evaluated for constriction or narrowing. The presence of these vessels can significantly alter surgical planning and clinical management and should be carefully evaluated. Further information on evaluation of abnormal pulmonary artery anatomy can be found in Chap. 9 of this textbook (Right Ventricular Outflow Tract). Patients with heterotaxy syndrome may also have aortic arch hypoplasia, coarctation of the

3  Evaluation of Cardiac Malposition, Cardiac Segmental Approach, and Heterotaxy Syndrome

aorta, interrupted aortic arch, or even aortic atresia. As with any patient, the aortic arch may variably be left-sided or right-sided, easily determined on cardiac CT by examining if the aortic arch traverses to the left or right of the trachea. Patients with heterotaxy syndrome or complex congenital heart disease, however, may have a thoracic descending aorta that crosses the midline, opposite of the side of the aortic arch, at any level. Further information on evaluation of abnormal aortic arch anatomy can be found in Chap. 15 of this textbook (Aortic Arch Anomalies). Depending on the source of pulmonary artery or aortic arch blood flow, cardiac CT planning may vary widely, and any prior imaging studies should be carefully reviewed to optimize study planning. For example, if the patient is status-­ post cardiac surgical repair without residual shunts, then a triphasic injection technique and monitoring for enhancement of the left heart should provide excellent opacification of the pulmonary arteries and aorta. However, if the patient is a neonate with pulmonary atresia and PDA-­ dependent pulmonary blood flow, then typical contrast injection in a leg IV (to avoid beam-­ hardening artifact from dense contrast in the innominate veins or SVC) and monitoring for enhancement of the descending aorta should also provide excellent opacification of the pulmonary arteries and aorta, as both of these circulations are connected by the PDA.

Conclusion Cardiac CT is a powerful tool for diagnosis and management of patients with complex congenital heart disease. Utilizing a comprehensive, systematic descriptive scheme is essential to consistently describe the most important features of a wide variety of defects, ensure consistent evaluation from patient to patient, and communicate these abnormalities in a succinct and complete way to multidisciplinary teams. Complete and thorough diagnosis of all cardiac defects and associated lesions allows for optimal interventional planning and counseling of the patient and caregivers. We present our

35

method for describing the wide constellation of anatomic and cardiac defects typically found in complex patients, especially helpful in those with heterotaxy syndrome. Our terminology is consistent with those used by the International Society for Nomenclature of Paediatric and Congenital Heart Disease [6], in an effort to finally approach a universal system of terminology in congenital heart disease (while also mentioning other terminologies in popular use [3, 4, 8, 9]. The basic components that should be described, when possible, are cardiac position, pulmonary and abdominal (visceral) situs, systemic and pulmonary venous connections, atrial situs (or arrangement), ventricular situs and atrioventricular relationships, outflow tracts and ventriculoarterial alignments, and the great arteries.

References 1. Chen S-J, Li Y-W, Wang J-K, et al. Usefulness of electron beam computed tomography in children with heterotaxy syndrome. Am J Cardiol. 1998;81(2):188–94. https://doi.org/10.1016/S0002-­9149(97)00879-­5. 2. Van Praagh R.  Terminology of congenital heart disease. Glossary and commentary. Circulation. 1977;56(2):139–43. https://doi.org/10.1161/01. CIR.56.2.139. 3. Van Praagh R.  The importance of segmental situs in the diagnosis of congenital heart disease. Semin Roentgenol. 1985;20(3):254–71. https://doi. org/10.1016/0037-­198X(85)90009-­4. 4. Anderson RH.  Chapter 1  - Terminology. In: Anderson RH, Baker EJ, Penny DJ, et  al., editors. Paediatric cardiology (Third Edition). Churchill Livingstone; 2010. p.  3–16. https://doi.org/10.1016/ B978-­0-­7020-­3064-­2.00001-­1. 5. Geva T.  Nomenclature and segmental approach to congenital heart disease. In: Echocardiography in pediatric and congenital heart disease. Wiley; 2009. p.  22–33. https://doi.org/10.1002/9781444306309. ch3. 6. Jacobs JP, Anderson RH, Weinberg PM, et  al. The nomenclature, definition and classification of cardiac structures in the setting of heterotaxy. Cardiol Young. 2007;17 Suppl 2:1–28. https://doi.org/10.1017/ S1047951107001138. 7. Cohen MS, Anderson RH, Cohen MI, et  al. Controversies, genetics, diagnostic assessment, and outcomes relating to the heterotaxy syndrome. Cardiol Young. 2007;17(S4):29–43. https://doi.org/10.1017/ S104795110700114X.

36 8. O’Leary PW, Hagler DJ.  Chapter 53: Cardiac malpositions and abnormalities of atrial and visceral situs. In: Moss and Adams’ heart disease in infants, children, and adolescents (Volume 1 Und 2) Including the fetus and young adult. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2016. p. 1195–216. 9. Freedom RM.  The asplenia syndrome: a review of significant extracardiac structural abnormalities in 29 necropsied patients. J Pediatr. 1972;81(6):1130– 3. https://doi.org/10.1016/S0022-­3476(72)80244-­0. 10. Moller JH, Nakib A, Anderson RC, Edwards JE. Congenital cardiac disease associated with polysplenia. Circulation. 1967;36(5):789–99. https://doi. org/10.1161/01.CIR.36.5.789. 11. Yim D, Nagata H, Lam CZ, et al. Disharmonious patterns of heterotaxy and isomerism. Circ Cardiovasc Imaging. 2018;11(2):006917. https://doi.org/10.1161/ CIRCIMAGING.117.006917.

M. D. Patel 12. Lopez L, Huhta JC.  Systemic venous anomalies. In: Echocardiography in pediatric and congenital heart disease. Wiley; 2009. p.  143–57. https://doi. org/10.1002/9781444306309.ch10. 13. Uemura H, Ho SY, Devine WA, Kilpatrick LL, Anderson RH. Atrial appendages and venoatrial connections in hearts from patients with visceral heterotaxy. Ann Thorac Surg. 1995;60(3):561–9. https://doi. org/10.1016/0003-­4975(95)00538-­V. 14. Muñoz-Castellanos L, De la Cruz MV, Cieśliński A.  Double inlet right ventricle. Two pathological specimens with comments on embryology. Br Heart J. 1973;35(3):292–7. 15. Wright GE, Maeda K, Silverman NH, Hanley FL, Roth SJ. Chapter 49: Double outlet right ventricle. In: Moss and Adams’ heart disease in infants, children, and adolescents (Volume 1 Und 2) including the fetus and young adult. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2016. p. 1201–15.

4

Systemic Venous Anomalies Santosh C. Uppu

Introduction

Embryology

Systemic venous anomalies include a wide range of abnormalities with an incidence of 0.3–0.4% in the general population, and its incidence increases to 2–5% in patients requiring cardiac intervention [1]. Heterotaxy syndromes are associated with a significantly higher incidence of systemic venous anomalies occurring in up to 70% of the cases [2]. Bilateral superior vena cava represents the majority of the systemic venous anomalies and is of no hemodynamic significance as the deoxygenated blood ultimately returns to the right atrium. Other variants like retroaortic innominate vein and interrupted inferior vena cava with azygos continuation still ultimately drain venous blood back to the right atrium. Some variants such as left superior vena cava emptying into the left atrium or partial anomalous drainage of pulmonary veins are of hemodynamic significance and would need to be intervened upon. Knowledge of systemic venous anomalies is necessary for appropriate planning of the interventions [1].

Understanding systemic venous embryology is of paramount importance to appreciate various anomalies. Venous system develops from three pairs of major veins: the vitelline, umbilical, and the cardinal veins. The umbilical veins first appear at 3 weeks of gestation to transport oxygenated blood to the developing fetus. The right umbilical vein disappears over time, and the left umbilical vein develops communication with right hepatocardiac channels that ultimately becomes ductus venosus. Portal hepatic venous system along with the ductus venosus regulates the placental flow into the fetus. Postnatally ductus venosus becomes a fibrous ligamentum teres. Vitelline veins that carry blood from yolk sac develop along with the umbilical veins. Cardinal veins are the last to develop and drain the embryo proper. By the fourth week, all these veins enter the right and left horns of sinus venosus; the initial communication between the sinus venosus and the atrium is broad; and by the end of the fourth week, this communication shifts to the right [1]. During the fifth week, the left vitelline veins regress along with the left horn of sinus venosus as the right vitelline veins become dominant. At around 10 weeks, the left cardinal vein regresses, and the left sinus horn is represented postnatally by the coronary sinus and oblique vein of the left atrium that empty into the right atrium [3, 4].

S. C. Uppu (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_4

37

S. C. Uppu

38

The right cardinal vein drains the embryo with anterior cardinal veins draining the head and the posterior cardinal veins draining the rest of the embryo. Anastomosis between the right and left cardinal veins in the eighth week forms the innominate vein, and right superior vena cava is formed by right common and anterior cardinal veins [4, 5]. The inferior vena cava has complex development from different venous systems between the sixth and eighth weeks. The supra- and subcardinal veins are extensively interconnected. Posterior cardinal veins and the left subcardinal veins regress. The right subcardinal vein becomes the hepatic portion of the IVC, and failure of the right subcardinal vein to connect with the liver results in interrupted IVC with resultant shunting of blood in the right supracardinal vein that creates a dilated azygos vein [2].

Left Superior Vena Cava Persistent left superior vena cava (LSVC) is the most common systemic venous anomaly with an incidence of 0.3% [4]; the incidence increases with associated congenital heart defects and is commonly seen in tetralogy of Fallot, atrioven-

a

tricular septal defects, and heterotaxy syndromes. It results from failure of regression of the left anterior cardinal vein. The presence of bilateral superior vena cava is more common than the absent right superior vena cava (Fig.  4.1). The left superior vena cava commonly drains into the dilated coronary sinus that empties into the right atrium as such there is no hemodynamic significance. The variations of LSVC include bilateral SVC of variable size with or without a bridging vein, absent right SVC resulting from obliteration of the right common cardinal, proximal part of the anterior cardinal veins along with persistence of the left anterior cardinal vein, and LSVC draining directly into the left atrium (8% of LSVC) [1, 2, 5]. LSVC draining into the left atrium results from the partial or complete unroofing of the coronary sinus; there is a coronary sinus opening in the right atrium that functions as an atrial septal defect (Raghib syndrome) [4, 6]. This results in desaturated blood entering the systemic circulation and cyanosis. If the degree of cyanosis is not clinically obvious, these patients can present with polycythemia, paradoxical emboli, stroke, or brain abscess. In some cases, the atrial septal communication is not present.

b AO

LSVC

RSVC

RA CS

Fig. 4.1  Infant with bilateral superior vena cava with persistent left superior vena cava draining to dilated coronary sinus. Coronal (a) and sagittal (b) reconstructed images show bilateral superior vena cavae with persistent left

superior vena cava draining to dilated coronary sinus. RSVC right superior vena cava, LSVC persistent left superior vena cava, RA right atrium, CS dilated coronary sinus, AO aortic root

4  Systemic Venous Anomalies

39

Diagnosis Persistent LSVC can be diagnosed with routine echocardiography in patients with good acoustic windows. In those with suboptimal echocardiographic images, one can consider transesophageal or transthoracic echocardiography with agitated saline contrast in the left arm to help understand the venous course. Cross-sectional imaging with cardiac MRI or cardiac CT can be considered if the echocardiography is not diagnostic and if there are associated cardiac lesions. Contrast injection in the left arm will help enhance the LSVC; a delayed venous phase also helps show the entire systemic venous system. Prospective CT techniques can help reduce the radiation dose.

Management Isolated LSVC with no hemodynamic significance does not need any intervention. Unroofed coronary sinus with left atrial drainage of LSVC with atrial septal communication will require surgical repair. LSVC to the left atrium without atrial septal communication and a bridging vein can behave as an atrial septal defect with left to right shunting due to differential atrial pressure and might not be cyanotic, but these patients are still at risk for complications due to intermittent

a

right to left shunting, and these can be closed percutaneously [7–9]. Knowledge of left superior vena cava with associated heart defects is essential for planning cannulation and interventional strategies [10].

I nterrupted Inferior Vena Cava with Azygos Continuation The inferior vena cava (IVC) has a complex embryologic development originating from five different venous systems [3]. Interrupted IVC results when the right subcardinal vein fails to establish connections with the right hepatocardiac veins as such the hepatic portion of the IVC is absent; the right supracardinal vein becomes dilated which develops into an azygos vein and routes the blood from the lower body ultimately draining into the right superior vena cava (Fig. 4.2). Variations of dilated azygos or hemiazygos veins are reported depending on which venous system dilates [5]. Interrupted IVC usually occurs as part of the heterotaxy syndrome, most commonly with left atrial isomerism (Table  4.1) but rarely can occur with visceral situs solitus. Hepatic veins still drain directly to the atria [2]. Symptoms are dependent on associated cardiac lesions. Knowledge of interrupted IVC is essential for surgical cannulation, surgical procedures as part of single-ventricle surgery, or interventional procedures.

b AZ

RA HV

Fig. 4.2  A 2-year-old child with interrupted inferior vena cava and azygous continuation after Kawashima procedure. Parasagittal reformatted image showing azygous

vein (a) and coronal reconstructed image (b) showing hepatic veins directly draining to right atrium. AZ azygous vein, RA right atrium, HV hepatic veins

S. C. Uppu

40 Table 4.1  Systemic venous anomalies commonly seen in heterotaxy syndromes Systemic venous anomaly Interrupted IVC Hepatic veins entering Atria directly Bilateral SVC Unroofed coronary sinus Bilateral IVC

Right atrial isomerism (asplenia) +/− +

Left atrial isomerism (polysplenia) ++++ ++++

+++ ++++

++ ++

+

–

Management Interrupted IVC is managed along with the cardiac lesions associated with the heterotaxy syndromes [12]. The presence of IVC interruption complicates cardiac catheterization or electrophysiologic procedures. Patients requiring single-­ventricle surgery involve a modification of the Glenn procedure (Kawashima modification) as the entire systemic venous flow except for hepatic veins is routed to the pulmonary arteries [1, 13, 14].

Diagnosis

Other Systemic Venous Interrupted IVC can be diagnosed by echocar- Malformations diography either pre- or postnatally. Associated cardiac lesions or presence of heterotaxy syndrome should make one carefully evaluate venous anomalies [11]. Given the wide spectrum of lesions often associated with heterotaxy syndrome, one might consider cross-sectional imaging using cardiac MRI or cardiac CT for thorough evaluation. Contrast injection in the foot will help enhance the lower veins and dilated azygos veins; a delayed venous phase also helps show the entire systemic venous system. Prospective CT techniques can help reduce the radiation dose. CT study can be performed in newborn infants without sedation by swaddling the child and using modern scanners with recent software that can acquire the image in fewer heart beats without the need for a breath hold. CT imaging might also aid in understanding complex intracardiac anatomy in heterotaxy patients specially to understand great vessel relation to the ventricles and septal defects. There is a role for cardiac CT to evaluate before or after subsequent surgical interventions if the patient is undergoing multiple procedures. Patients with MRI incompatible hardware (pacemaker, devices, etc.) might be better CT candidates. CT also has the advantage of better visualizing the extracardiac structures.

Drainage of the right superior vena cava (RSVC) to the left atrium or both atria has been rarely reported, and it results from the leftward displacement of the right horn of the sinus venosus as such the RSVC empties either into both or left atrium. It is believed that this is a variation of the superior sinus venosus defect [2, 4, 15, 16]. This anomaly results in cyanosis and associated manifestations. This anomaly might be difficult to diagnose by echocardiography alone and might be better visualized by cardiac CT or MRI. Retroaortic innominate vein is a rare venous anomaly where the innominate vein courses behind the ascending aorta to join the RSVC, and it is often reported with other congenital heart defects such as tetralogy of Fallot, truncus arteriosus, atrioventricular septal defects, right aortic arch, etc. [17]. This anomaly can be suspected by echocardiography and can be confirmed by cross-­ sectional imaging. Bilateral IVCs are rare and result from the persistence of right and left supracardinal veins; it is reported in heterotaxy syndromes more commonly associated with right atrial isomerism [18]. The clinical significance depends on how these two IVCs enter the heart. Cross-sectional imaging is preferred for this complex anomaly [2, 4].

4  Systemic Venous Anomalies

References 1. Gandy K, Hanley F. Management of systemic venous anomalies in the pediatric cardiovascular surgical patient. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2006:63–74. https://doi.org/10.1053/j. pcsu.2006.02.004. 2. Lopez L, Chambers S.  Systemic venous anomalies. In: Lai WW, Mertens LL, Cohen MS, Geva T, editors. Echocardiography in pediatric and congenital heart disease: from fetus to adult. Oxford, UK: Wiley; 2016. p.  180–96. https://doi.org/10.1002/9781118742440. ch10. 3. Sadler TW.  Langman’s medical embryology. 12th ed. Philadelphia: Lippincott Williams & Wilkins; 2011. 4. Tal G.  Abnormal systemic venous connections. In: Allen HD, Shaddy RE, Penny DJ, Feltes TF, Cetta F, editors. Moss and Adams’ heart disease in infants, children, and adolescents: including the fetus and young adult. 9th ed. Two Commerce Square, 2001 Market Street, Philadelphia, 19103: Lippincott Williams & Wilkins; 2016. pp. 911–33. 5. Tacy TA, Silverman NH.  Systemic venous abnormalities: embryologic and echocardiographic considerations. Echocardiography. 2001;18:401–13. https://doi.org/10.1046/j.1540-­8175.2001.00401.x. 6. Raghib G, Ruttenberg HD, Anderson RC, Amplatz K, Adams P, Edwards JE.  Termination of left superior vena cava in left atrium, atrial septal defect, and absence of coronary sinus; a developmental complex. Circulation. 1965;31:906–18. https://doi. org/10.1161/01.cir.31.6.906. 7. Troost E, Gewillig M, Budts W. Percutaneous closure of a persistent left superior vena cava connected to the left atrium. Int J Cardiol. 2006;106:365–6. https://doi. org/10.1016/j.ijcard.2005.02.015. 8. Wang B, Prejean SP, Singh SP, Ahmed MI, Law MA. Percutaneous repair of raghib syndrome. JACC Cardiovasc Interv. 2020;13:e159–60. https://doi. org/10.1016/j.jcin.2020.04.057.

41 9. Meadows WR, Sharp JT. Persistent left superior vena cava draining into the left atrium without arterial oxygen unsaturation. Am J Cardiol. 1965;16:273–9. https://doi.org/10.1016/0002-­9149(65)90484-­4. 10. Savu C, Petreanu C, Melinte A, Posea R, Balescu I, Iliescu L, et  al. Persistent left superior vena cava  accidental finding. In Vivo. 2020;34:935–41. https:// doi.org/10.21873/invivo.11861. 11. Lytrivi ID, Lai WW.  Cardiac malpositions and Heterotaxy syndrome. In: Lai WW, Mertens LL, Cohen MS, Geva T, editors. Echocardiography in pediatric and congenital heart disease: from fetus to adult. Oxford, UK: Wiley; 2016. p. 558–83. 12. Van Praagh S.  Cardiac Malpositions and the Heterotaxy syndromes. In: Keane JF, Lock JE, Fyler DC, editors. Nadas’ pediatric cardiology. Second. Philadelphia: Saunders; 2006. 13. Kawashima Y, Kitamura S, Matsuda H, Shimazaki Y, Nakano S, Hirose H.  Total cavopulmonary shunt operation in complex cardiac anomalies. A new operation. J Thorac Cardiovasc Surg. 1984;87:74–81. 14. Vollebregt A, Pushparajah K, Rizvi M, Hoschtitzky A, Anderson D, Austin C, et al. Outcomes following the Kawashima procedure for single-ventricle palliation in left atrial isomerism. Eur J Cardiothorac Surg. 2012;41:574–9. https://doi.org/10.1093/ejcts/ezr003. 15. Gursoy M, Salihoglu E, Ozcobanoglu S, Ozkan S, Celiker A.  Isolated right superior vena cava draining into the left atrium. J Card Surg. 2012;27:623–5. https://doi.org/10.1111/j.1540-­8191.2012.01509.x. 16. Alghamdi MH, Elfaki W, Al-Habshan F, Aljarallah AS.  Bilateral superior vena cava with right superior vena cava draining into left atrium. J Saudi Heart Assoc. 2015;27:123–6. https://doi.org/10.1016/j. jsha.2014.10.001. 17. Kohli U.  Isolated retroaortic innominate vein and right aortic arch: a case report and review of literature. Cardiol Young. 2019;29:1091–3. https://doi. org/10.1017/S1047951119001380. 18. Hirsch DM, Chan KF.  Bilateral inferior vena cava. JAMA. 1963;185:729–30. https://doi.org/10.1001/ jama.1963.03060090061024.

5

Anomalous Pulmonary Venous Connections and Cor Triatriatum Li Xiong

Introduction Congenital anomalies of the pulmonary venous connections are a heterogeneous group of malformations where the pulmonary veins drain to a location other than the left atrium. Partial anomalous pulmonary venous connections (PAPVC) occur when some but not all pulmonary veins return anomalously, and total anomalous pulmonary venous connections (TAPVC) occur when all pulmonary veins return anomalously. These are rare lesions with reported incidence of 6 per 100,000 for TAPVC or 0.6% of total congenital heart disease and 1 per 100,000 or 0.1% of total congenital heart disease in a large population study in the United States [1]. These lesions result in a left to right shunt where the clinical presentation reflects the number of pulmonary veins involved and the presence or absence of pulmonary venous obstruction. Cor triatriatum is an anomaly of pulmonary venous drainage that consists of a membrane that separates pulmonary veins that connect to the left atrium from the mitral valve, which may result in obstruction to pulmonary venous return. While echocardiography is often the initial study L. Xiong (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

to evaluate anomalous pulmonary venous connections, echocardiography may be limited in its assessment of extracardiac vascular structures. Cardiac CT has emerged as an important modality to delineate pulmonary venous anatomy both prior to intervention and as part of monitoring and reassessment following intervention [2, 3].

Embryology and Anatomy Early in gestation, the primitive lung buds develop from the foregut and are drained by the splanchnic plexus, which forms the pulmonary vascular bed. The pulmonary vascular bed then drains to the umbilicovitelline and cardinal venous systems. The common pulmonary vein is formed, whose origin is controversial, and drains the pulmonary vascular bed to the developing left atrium. At this time in development, the pulmonary vasculature drains both to the heart and to the systemic veins. The connections to the umbilicovitelline and cardinal veins then regress, leaving the drainage of the pulmonary vasculature to the heart. Subsequently, individual pulmonary veins, typically two on each side, develop and drain to the common pulmonary vein, which becomes incorporated into the left atrium [3–6]. Abnormalities in this development result in the various forms of anomalous pulmonary venous connections seen. Failure of the right cardinal vein to regress results in anomalous connections to the right superior

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_5

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vena cava or the right atrium. Failure of the left cardinal vein to regress results in anomalous connections to the left innominate vein or coronary sinus. Failure of the umbilicovitelline veins to regress results in infracardiac anomalous connections to the hepatoportal system, ductus venosus, or inferior vena cava. Abnormalities in the incorporation of the common pulmonary vein to the left atrium resulting from the formation of two chambers—an accessory atrial chamber that receives pulmonary venous return and the left atrium proper—are generally accepted as the embryologic origin of the various forms of cor triatriatum sinister [2, 4–7]. Anomalous pulmonary venous return is also seen in association with certain cardiac lesions, such as sinus venosus atrial septal defects and Turner syndrome associated with PAPVC and atrial isomerism with right atrial isomerism associated with TAPVC and absence of the coronary sinus and left atrial isomerism associated with ipsilateral pulmonary venous connections (two pulmonary veins draining to the left-sided atrium and two pulmonary veins draining to the right-­ sided atrium) [3, 8, 9]. Indeed, a meta-analysis on prenatal diagnoses of TAPVC found an estimated 28% of patients diagnosed prenatally with TAPVC had other congenital heart diseases [10]. A form of PAPVC where the pulmonary venous return of one lung, usually the right lung, drains anomalously, commonly to the inferior vena cava, is termed scimitar syndrome due to the crescent-like appearance of the anomalous pulmonary vein and is often associated with abnormalities of the corresponding lung, such as pulmonary sequestration and lung hypoplasia, and its arterial supply [3, 11, 12]. TAPVC is classified based on the location of the anomalous pulmonary venous connection: supracardiac (such as left innominate vein or superior vena cava), intracardiac (such as right atrium or coronary sinus), infracardiac (such as the hepatic veins, portal veins, ductus venosus, or inferior vena cava), or mixed (a combination of the above). Supracardiac TAPVC is the most common form of TAPVC, whereas infracardiac TAPVC is most likely to present in the neonatal period with pulmonary venous obstruction [3, 4]. There are various

proposed classification schemes for cor triatriatum, which involve describing the types of cor triatriatum based on the type of communication between the accessory atrial chamber and the left atrium, location of the atrial septal defect (if present), and pulmonary venous connections [2, 7].

Diagnosis The initial diagnosis or suspicion for TAPVC, PAPVC, and cor triatriatum is often made via echocardiography. Echocardiography shows pulmonary veins that do not drain to the left atrium and can often demonstrate the anomalous connection to the aforementioned various structures. As a consequence, in TAPVC, echocardiography also often demonstrates a small left atrium and dilated right heart structures as well as dilation of the structure receiving the anomalous pulmonary venous connection. Narrowing of a vertical vein, flow acceleration by color Doppler, and increased mean gradient with a non-phasic flow pattern by spectral Doppler are suggestive of pulmonary venous obstruction [13, 14]. While anatomic determination of the anomalous pulmonary venous anatomy and assessment for pulmonary venous obstruction and intracardiac anatomy and function can be made via echocardiography, full delineation of extracardiac vascular structures, particularly its distal course, may be limited by echocardiography, particularly in cases of poor acoustic windows. Cardiac CT thus plays an important role in confirming the diagnosis or in delineation of pulmonary venous anatomy in cases where pulmonary venous anatomy cannot be fully determined by echocardiography [14– 16]. Cor triatriatum sinister is seen by the presence of a membrane in the left atrium that separates it into two chambers, which may also be associated with anomalous pulmonary venous connections. Cardiac CT not only delineates the two chambers and its communication, if present, but also the pulmonary venous connections [2, 7]. Prior to intervention, cardiac CT demonstrates pulmonary venous anatomy and the presence or absence of anatomic obstruction (Figs. 5.1, 5.2, 5.3, 5.4, 5.5, and 5.6).

5  Anomalous Pulmonary Venous Connections and Cor Triatriatum

a

45

b

C

c

LP LB

Fig. 5.1  Supracardiac total anomalous pulmonary venous connection consisting of two right-sided pulmonary veins and the left lower pulmonary vein draining to a confluence that drains via a vertical vein (VV) to the left innominate vein on coronal view (a), volume rendered reconstructed image (b) and (c) pulmonary venous confluence shows where the lower pulmonary veins come together behind

the atrium. The left upper pulmonary vein drains directly to the vertical vein. There is obstruction of the vertical vein at the level of the left pulmonary artery and left mainstem bronchus, consistent with a “vise” (asterisk), in parasagittal view [14]. LP left pulmonary artery, LB left mainstem bronchus, C pulmonary venous confluence

L. Xiong

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a

b

PV

PV

PV

PV

HPV

HPV

Fig. 5.2  Infracardiac total anomalous pulmonary venous connection consisting of all pulmonary veins draining to a dilated descending vertical vein (VV) in coronal view (a)

and volume rendered reconstructed image (b). PV pulmonary veins, HPV hepatic portal venous system

Cardiac CT is also used post-intervention to monitor for and assess extent of re-stenosis of the pulmonary veins or anastomosis site (Fig. 5.7). Cor triatriatum can also be delineated by cardiac CT (Fig. 5.8).

usual contrast dose of 1.5–2  mL/kg in infants and children up to maximal dosage in older adolescents and adults. The contrast medium is typically delivered via dual-head power injector at an injection rate of 0.8–1 mL/second in neonates and infants and up to 4 mL/second in older adolescents and adults, depending on patient weight and size of peripheral intravenous access [15, 17–19]. The location of venous access depends on the suspected lesion and age and size of the patient. In neonates, infants, and toddlers, a lower extremity peripheral intravenous line is preferred in cases of infracardiac TAPVC to prioritize enhancement along the anomalous connection, whereas supracardiac and intracardiac TAPVC could be delineated either via a lower extremity peripheral intravenous line with a biphasic injection with an equal-sized bolus of saline solution

 atient Preparation, Contrast P Medium, and Cardiac CT Technique The patient should be positioned in the scanner at its isocenter with the arms positioned over the patient’s head and the electrocardiographic electrodes and any other tubing, wires, or equipment positioned out of the desired thoracic field of view to both minimize radiation dose and artifact. Iso-osmolar, non-ionic, and water-soluble contrast agents are preferred with the total

5  Anomalous Pulmonary Venous Connections and Cor Triatriatum

a

47

b

IV

SVC

PV

c

PV PV

Fig. 5.3  Mixed-type total anomalous pulmonary venous connection consisting of the right-sided pulmonary veins and left lower pulmonary vein draining to a confluence that drains to the left innominate vein via a vertical vein (VV). The left upper and left lingular pulmonary veins drain to the vertical vein (VV) as seen on coronal view (a). There is also a connection between the pulmonary venous

confluence and a dilated coronary sinus (asterisk), resulting in both supracardiac and intracardiac anomalous pulmonary venous connections, as seen in the coronal view (b) and volume rendered reconstructed image (c). PV pulmonary vein, IV innominate vein, SVC superior vena cava

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a

b

SVC

Fig. 5.4  Partial anomalous pulmonary venous connection in the context of a superior sinus venosus atrial septal defect with the right upper and right middle pulmonary veins draining to the right superior vena cava (right upper

a

pulmonary vein shown by asterisk) (a) and the right lower pulmonary vein overriding the sinus venosus atrial septal defect (arrow) (b). SVC superior vena cava

b

IV IV

Fig. 5.5  Partial anomalous pulmonary venous connection consisting of the left upper pulmonary vein (asterisk) draining to a dilated left innominate vein on double

SVC

oblique view (a) and volume rendered reconstructed image (b). IN innominate vein, SVC superior vena cava

5  Anomalous Pulmonary Venous Connections and Cor Triatriatum

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Fig. 5.6  Partial anomalous pulmonary venous connection in the context of scimitar syndrome with right-sided pulmonary veins draining together at the level of the diaphragm (asterisk) into the posterior aspect of the inferior vena cava on coronal view (a), parasagittal view (b), and

volume rendered reconstructed image (c). In this patient, there was also associated right lung hypoplasia and intralobar pulmonary sequestration fed by a “scimitar” artery from the celiac trunk (gray arrow)

immediately following the contrast dose or via an upper extremity peripheral intravenous line (left upper extremity if suspected anomalous connection to the left innominate vein and right upper extremity if suspected anomalous connection to

the right superior vena cava) with a triphasic injection (a triphasic injection with dilution of the latter portion of the contrast dose with saline solution (0.9% sodium chloride) is utilized to minimize high-density contrast artifact (streak

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a

b

Fig. 5.7  Repaired intracardiac total anomalous pulmonary venous connection with moderate stenosis (black arrow) of the left common pulmonary vein at its junction

to the pulmonary venous confluence and mildly dilated right common pulmonary vein on coronal view (a) and volume rendered reconstructed image (b)

b

a RV

RA

LV

AO

LA PV PC

VSD RV

LV

c

AO

RV LV

Fig. 5.8  Neonate with cor triatriatum, double-outlet right ventricle with aorta arising from right ventricle, and pulmonary atresia. Axial reconstructed image showing cor triatriatum with membrane in the left atrium separating posterior chamber which receives pulmonary veins (a).

Coronary multiplanar reconstructed image (b) and volume rendered reconstruction (c) showing right ventricle giving rise to the aorta. PC posterior chamber, PV pulmonary vein, LA left atrium, RA right atrium, RV right ventricle, LV left ventricle, AO aorta, VSD ventricular septal defect

5  Anomalous Pulmonary Venous Connections and Cor Triatriatum

artifact); the total contrast dose is then immediately followed by an equal-sized bolus of saline solution). In older children, adolescents, and adults, a triphasic injection as described above via an upper extremity peripheral intravenous line is used. Automatic bolus tracking technique with the reference cardiovascular structure of the left atrium monitored at near real time until reaching a predetermined threshold opacification of 100–150 Hounsfield units or visual monitoring with manual triggering can be used after contrast injection. An average scan delay of 5–8 seconds is used. Dual-source multidetector CT has ­significantly shortened scan time such that the need for sedation to avoid motion artifact in uncooperative patients is uncommon, and neonates and young infants may be adequately soothed with a small amount of oral sucrose solution during the study. While cardiac magnetic resonance imaging can also delineate pulmonary venous anatomy and avoids ionizing radiation, the shorter scan duration and potential avoidance of sedation compared to cardiac magnetic resonance imaging are particularly useful in the critically ill patient. The preferred cardiac CT technique is prospective electrocardiographic (ECG)-gated cardiac CT to minimize radiation dose compared to retrospective ECG-gated cardiac CT, and low-dose protocol based on the patient’s weight allows for further minimization of radiation dose while maintaining adequate resolution for anatomic delineation [14, 15, 17–19].

Management Approach For TAPVC, surgical repair is indicated and offers definitive correction. Timing of surgery is dependent on the clinical presentation, which in turn is dependent on the presence or absence of pulmonary venous obstruction and the adequacy of a right to left shunt, as well as patient comorbidities. Patients with obstructed TAPVC often present with symptoms of severe respiratory distress or failure, pulmonary edema, pulmonary hypertension, and acidosis and low cardiac output and require emergent surgery. In patients

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without significant pulmonary venous obstruction but other comorbidities that negatively affect surgical candidacy, the timing of surgical repair is balanced between management of these comorbidities while monitoring for the development of heart failure symptoms from left to right shunting and pulmonary venous obstruction; in some cases, percutaneous interventions may offer temporizing measures until definitive surgical ­ repair can be undertaken [4, 5, 20]. The surgical approach to TAPVC repair varies based on the type of TAPVC and the patient’s individual anatomy in terms of the relationship of the pulmonary venous anatomy to the left atrium but results in the creation of unobstructed drainage of the pulmonary veins to the left atrium and aims to avoid the development of pulmonary venous obstruction [20]. For PAPVC, the need for and timing of intervention generally depend on clinical presentation, where patients with one anomalous pulmonary vein and no other sources of left to right shunting rarely have significant left to right shunting to result in symptoms or hemodynamic changes, whereas patients with only one pulmonary vein connected normally to the left atrium with remaining pulmonary veins connected anomalously may present similarly to TAPVC.  Surgical repair is generally indicated in the presence of symptoms from left to right shunting, such as pulmonary over-circulation, respiratory distress, and failure to thrive, and signs of hemodynamically significant left to right shunting, such as right heart dilation or the ratio of pulmonary blood flow to systemic blood flow (Qp:Qs) of 1.5 or higher. Surgical repair of PAPVC may also be indicated at the time of repair of associated congenital heart defects, such as a sinus venosus atrial septal defect [5, 21, 22]. For cor triatriatum sinister, surgical repair is generally indicated based on symptoms related to the degree of obstruction to pulmonary venous return and pulmonary hypertension as long-­standing obstructive cor triatriatum sinister can lead to pulmonary venous obstruction disease. Transcatheter interventions, such as balloon angioplasty of the membrane opening,

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have been reported, including in cases of suboptimal surgical candidacy, such as pregnancy [7, 23].

Outcomes Unrepaired TAPVC has a high mortality rate, reported at ~80% within the first year of life, whereas unrepaired PAPVC depends on the number of anomalous pulmonary veins involved, where one anomalous pulmonary vein without other sources of left to right shunting and in the absence of symptoms is expected to have a similar course as an uncomplicated atrial septal defect [5, 24]. The outcomes of unrepaired scimitar syndrome vary by age of presentation with those who present in infancy tending to have more severe symptoms, associated lung defects, and pulmonary hypertension as opposed to those who present in adulthood. Overall mortality rate for unrepaired scimitar syndrome has been reported at 55% in unrepaired infants and low in unrepaired adults. Furthermore, single-ventricle physiology, associated congenital heart defects, and pulmonary venous obstruction were also risk factors for mortality in scimitar syndrome patients [5, 12]. Overall long-term mortality following surgical repair has been reported at 5–23% with higher mortality described in patients with infracardiac and mixed types of TAPVC compared to supracardiac and intracardiac types of TAPVC and most mortality occurring in the first year following surgery. Outcomes of TAPVC are also influenced by comorbidities, including younger age at time of repair, lower weight at time of repair, pulmonary venous obstruction, and associated congenital heart disease. In particular, heterotaxy syndrome and single-ventricle physiology have been reported as predictors for post-operative morbidity, and mortality with post-operative mortality in patients with single-ventricle physiology has been reported at 21–55% [16, 20, 24–26]. Outcomes of surgical repair of PAPVC in the absence of associated complex congenital heart disease are generally excellent with low mortality and improvement in hemodynamic findings, such

as improvement right heart dilation [27, 28]. In scimitar syndrome, outcomes of surgical repair have been reported from 0% to 64% with reported higher mortality in infants than adults [12, 29]. Patients with repaired PAPVC and repaired TAPVC warrant long-term follow-up for monitoring for complications, such as arrhythmias, superior vena cava stenosis for surgical repairs involving the superior vena cava, and post-­ ­ operative pulmonary venous obstruction, the incidence of which has been reported from 5% to 18% [4, 16, 26, 27, 30]. Early post-­ operative pulmonary venous obstruction has been reported as a predictor of mortality [4, 16, 26]. Cardiac CT is useful in the assessment for pulmonary venous and superior vena cava obstruction to characterize the location of and degree of stenosis (Fig.  5.7). Post-operative pulmonary venous obstruction and superior vena cava obstruction are managed via percutaneous interventions, including balloon angioplasty and stent angioplasty, and surgical re-intervention [4]. Surgical repair of cor triatriatum has been reported with low mortality with survival at 83–88% at 10–15 years with degree of symptoms and complexity of associated congenital heart disease reported to impact post-surgical survival. Post-operative follow-up monitors for complications such as arrhythmia and residual or recurrent obstruction [7, 23, 31].

References 1. Egbe A, Uppu S, Stroustrup A, Lee S, Ho D, Sriavstava S. Incidences and sociodemographics of specific congenital heart diseases in the United States of America: an evaluation of hospital discharge diagnoses. Pediatr Cardiol. 2014;35:975–85. 2. Razek A, Al-Marsafawy H, Elmansy M, El-Latif M, Sobh D.  Computed tomography angiography and magnetic resonance angiography of congenital anomalies of pulmonary veins. J Comput Assist Tomogr. 2019;43:399–405. 3. Dyer K, Hlavacek A, Meinel F, De Cecco C, McQuiston A, Schoepf U, et al. Imaging in congenital pulmonary vein anomalies: the role of computed tomography. Pediatr Radiol. 2014;44:1158–68. 4. Files M, Morray B.  Total anomalous pulmonary venous connection: preoperative anatomy, physiology, imaging, and interventional management of

5  Anomalous Pulmonary Venous Connections and Cor Triatriatum postoperative pulmonary venous obstruction. Semin Cardiothorac Vasc Anesth. 2017;21(2):123–31. 5. Brown D, Geva T. Anomalies of the pulmonary veins. In: Moss and Adams’ heart disease in infants, children and adolescents including the fetus and young adult. Philadelphia: Lippincott Williams & Wilkins. p. 881–910. 6. van den Berg G, Moorman A. Development of the pulmonary vein and the systemic venous sinus: an interactive 3D overview. PLoS One. 2011;6(7):e22055. 7. Jha A, Makhija N.  Cor triatriatum: a review. Semin Cardiothorac Vasc Anesth. 2017;21(2):178–85. 8. Frescura C, Ho S, Giordano M, Thiene G. Isomerism of the atrial appendages: morphology and terminology. Cardiovasc Pathol. 2020;47:107205. 9. Ho V, Bakalov V, Cooley M, Van P, Hood M, Burklow T, et al. Major vascular anomalies in Turner syndrome: prevalence and magnetic resonance angiographic features. Circulation. 2004;110(12):1694–700. 10. Paladini D, Pistorio A, Wu L, Meccariello G, Lei T, Tuo G, et  al. Prenatal diagnosis of total and partial anomalous pulmonary venous connection: multicenter cohort study and meta-analysis. Ultrasound Obstet Gynecol. 2018;52:24–34. 11. Turkvatan A, Guzeltas A, Tola H, Ergul Y. Multidetector computed tomographic angiography imaging of congenital pulmonary venous anomalies: a pictorial review. Can Assoc Radiol J. 2017;68:66–76. 12. Wang H, Kalfa D, Rosenbaum M, Ginns J, Lewis M, Glickstein J, et al. Scimitar syndrome in children and adults: natural history, outcomes, and risk analysis. Ann Thorac Surg. 2018;105:592–8. 13. Zhang Z, Zhang L, Xie F, Wang B, Sun Z, Kong S, et  al. Echocardiographic diagnosis of anomalous pulmonary venous connections: experience of 84 cases from 1 medical center. Medicine (Baltimore). 2016;95(44):e5389. 14. Vyas H, Greenberg S, Krishnamurty R.  MR imaging and CT evaluation of congenital pulmonary vein abnormalities in neonates and infants. Radiographics. 2012;32:87–98. 15. Dillman J, Yarram S, Hernandez R. Imaging of pulmonary venous developmental anomalies. AJR Am J Roentgenol. 2009;192(5):1272–85. 16. Shi G, Zhu Z, Chen J, Ou Y, Hong H, Nie Z, et  al. Total anomalous pulmonary venous connection: the current management strategies in a pediatric cohort of 768 patients. Circulation. 2017;135(1):48–58. 17. Booij R, Dijkshoorn M, van Straten M, du Plessis F, Budde R, Moelker A, et al. Cardiovascular imaging in pediatric patients using dual source CT. J Cardiovasc Comput Tomogr. 2016;10(1):13–21. 18. Secinaro A, Curione D, Mortensen K, Santangelo T, Ciancarella P, Napolitano C, et al. Dual-source computed tomography coronary artery imaging in children. Pediatr Radiol. 2019;49:1823–39.

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19. Pandey N, Sharma A, Jagia P. Imaging of anomalous pulmonary venous connections by multidetector CT angiography using third-generation dual source CT scanner. Br J Radiol. 2018;91(1092):20180298. 20. Vanderlaan R, Caldarone C.  Surgical approaches to total anomalous pulmonary venous connection. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2017;21:83–91. 21. Stout K, Daniels C, Aboulhosn J, Bozkurt B, Broberg C, Colman J, et al. 2018 AHA/ACC guideline for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association task force on clinical practice guidelines. Circulation. 2019;139(14):e698–800. 22. El-Kersh K, Homsy E, Daniels C, Smith J.  Partial anomalous pulmonary venous return: a case series with management approach. Respir Med Cas Rep. 2019;27:100833. 23. Rudiene V, Jhortshoj C, Glaveckaite S, Zakarkaite D, Petrulioniene Z, Gumbiene L, et  al. Cor triatriatum sinistrum diagnosed in the adulthood: a systematic review. Heart. 2019;105:1197–202. 24. Paladino M, Cavalli G, De Franceschi M, Mancuso D, Maschietto N, Vida V, et al. Surgical outcomes of total anomalous pulmonary venous connection repair: a 22-year experience. J Card Surg. 2014;29:678–85. 25. Domadia S, Kumar S, Votava-Smith J, Pruetz J.  Neonatal outcomes in total anomalous pulmonary venous return: the role of prenatal diagnosis and pulmonary venous obstruction. Pediatr Cardiol. 2018;39:1346–54. 26. Harada T, Nakano T, Oda S, Kado H. Surgical results of total anomalous pulmonary venous connection repair in 256 patients. Interact Cardiovasc Thorac Surg. 2019;28:421–6. 27. Suzuki K, Iwata Y, Hiramatsu T, Matsumura G, Hoki R, Nakanishi T, et  al. Mid- to long-term surgical outcomes of partial anomalous pulmonary venous connection. Gen Thorac Cardiovasc Surg. 2021;69(1):27–31. 28. Naimo P, d’Udekem Y, Brizard C, Konstantinov I.  Outcomes of repair of left partial anomalous pulmonary venous connection in children. Interact Cardiovasc Thorac Surg. 2015;21(2):254–6. 29. Gudjonsson U, Brown J. Scimitar Syndrome. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2006;9:56–62. 30. Lin H, Yan J, Wang Q, Li S, Sun H, Zhang Y, et al. Outcomes of the Warden procedure for partial anomalous pulmonary venous drainage. Pediatr Cardiol. 2020;41:134–40. 31. Saxena P, Burkhart H, Schaff H, Daly R, Joyce L, Dearani J.  Surgical repair of cor triatriatum sinister: the Mayo Clinic 50-year experience. Ann Thorac Surg. 2014;97:1659–63.

6

Septal Defects: Atrial Septal Defects, Ventricular Septal Defects, Atrioventricular Septal Defects, and Unroofed Coronary Sinus Mehul D. Patel

Introduction Defects of the atrial septum and ventricular septum are the most common types of congenital heart defects and also encompass less common but clinically significant defects such as atrioventricular septal defects, sinus venosus defects, and coronary sinus defects. Ventricular septal defects (VSDs) are the most common type of congenital heart defect, with a prevalence of 3.1 per thousand [1]; atrial septal defects (ASDs) are the second most common with a prevalence of 1.4 per thousand; and atrioventricular septal defects (AVSDs) are the seventh most common as a separate category, with a prevalence of 0.3 per thousand. ASD and VSDs may occur sporadically but are also associated with a multitude of genetic syndromes and mutations, including but not limited to 22q11.2 deletion syndrome, 1q21.1 deletion, trisomy 21, trisomy 18, trisomy 13, Holt-Oram syndrome, NKX2–NKX5 mutation, and GATA4 mutation [2]. AVSDs are commonly associated with trisomy 21 but can also be associated with CHARGE syndrome, Noonan synM. D. Patel (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

drome, Holt-Oram syndrome, 3p25 deletion, and 8p23.1 deletion [2].

Embryology and Anatomy Atrial Septal Defects The atrial septum first develops early in embryonic development after approximately 4 weeks 6f gestation [3] with growth of the septum primum from the roof of the central atrial chambers downward to the central endocardial cushions. This septum primum is crescent-shaped, with the leading edge composed of mesenchymal cells, and will eventually join into the central endocardial cushions to form the atrial septum primum [4]. During this development, a crescent-shaped muscular infolding of the atrial wall develops rightward of the septum primum. This infolding grows downward toward the central area of the atrial septum and forms the atrial septum secundum and the superior edge (also called the superior limbic band) of the fossa ovalis. In contrast, the atrial septum primum forms the valve on the left atrial side of the fossa ovalis. Gaps or defects in the atrial septum primum, or lack of the infolded walls that become the atrial septum secundum, create secundum atrial septal defects (Fig.  6.1). In contrast, a primum atrial septal defect is a defect of the endocardial cushion [3] at the cardiac crux resulting in a

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_6

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RV LV RA

LA

Fig. 6.1  Neonate with dextro-transposition of great arteries and atrial septal defect. Cardiac CT was performed to evaluate coronary arteries. The CT also shows secundum atrial septal defect (arrows). LV left ventricle, RV right ventricle, LA left atrium, RA right atrium

communicates from the left atrium, through the coronary sinus, and into the right atrium typically causing left to right shunting. However, the combination of a left SVC with a coronary sinus septal defect will cause both right to left shunting (from the left SVC draining directly into the left atrium) and left to right shunting (from the left atrium, through the coronary sinus, and into the right atrium)  – this is termed Raghib syndrome [7]. The true atrial septum may be completely intact but appear to have a defect where the orifice of the coronary sinus drains into the RA.

Ventricular Septal Defects

The ventricular septum first begins to divide the ventricular chambers between 4 and 7 weeks of gestation in the embryo [8]. This is a complex defect between the fossa ovalis of the atrial sep- process involving multiple events and cell types tum primum and the atrioventricular (AV) valves. and remains an area of much research and invesThis is considering a form of an atrioventricular tigation; only major events are briefly described septal defect and characterized by the primum here. Unique cells begin to form a ring around ASD and an AV valve abnormality (cleft of the between the embryonic left ventricle and right anterior mitral valve leaflet), but with no VSD ventricle, and further myocardialization of this component. tissue and the endocardial cushions create the A sinus venosus defect (Figs. 6.2 and 6.3) is a muscular interventricular septum and the outlet related but anatomically separate class of defects septum [9]. Mesenchymal cells from the atrial that can also cause interatrial shunting (either left septum primum and endocardial atrioventricular to right or right to left shunts). These are not cushions form the cardiac crux, inlet portion, and defects of the true atrial septum but created by a membranous portion of the ventricular septum defect from the superior vena cava (SVC), right [8]. Incomplete formation of these tissues leads atrium (RA), or inferior vena cava (IVC) to the to VSDs. right-sided pulmonary veins [5]. Anatomically, Anatomy of the ventricular septum has been the interatrial shunt communicates from the left long described with various descriptors and teratrium, through the right-sided pulmonary veins, minology systems; here we will focus on major and to the SVC or IVC. The embryologic basis types of VSDs and describe common terms for sinus venosus defects is not well understood recently published by the International Society but may begin from persistent pulmonary-to-­ for Nomenclature of Paediatric and Congenital systemic venous connections early in cardiac Heart Disease [10]. Interested readers are encourdevelopment, which described as veno-venous aged to refer to this publication and others for bridges [6]. Sinus venous defects can be sub- further details and elucidation of many forms of classified further by their connection to the sys- congenital heart defects. temic veins or RA: SVC-type, IVC-type, or sinus The ventricular septum anatomically is comvenous defect of the right atrial type [3]. plex and serves not only to wall the right ventriCoronary sinus septal defects are rare but cle from the left ventricle but also wall the LV result from partial or complete unroofing of the from the RA (with the membranous septum), coronary sinus, allowing an interatrial shunt that anchor papillary muscles (to the tricuspid valve

6  Septal Defects: Atrial Septal Defects, Ventricular Septal Defects, Atrioventricular Septal Defects…

a

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b SVC RV LV

RA

LA LA

RA

IVC

Fig. 6.2  A 2-year-old child with inferior sinus venosus atrial septal defect and partial anomalous drainage of right pulmonary veins. Cardiac CT axial reconstructed image (a) and sagittal reformatted image (b) showing inferior

a

sinus venosus defect (arrows) and partial anomalous right pulmonary vein. RA dilated right atrium, LA left atrium, IVC inferior vena cava, SVC superior vena cava, LV left ventricle, RV right ventricle

b SVC RPA AO

MPA

SVC RUPV

RA

RPA

LA

DAO

Fig. 6.3  A 3-year-old patient with superior sinus venosus atrial septal defect (arrows) with partial anomalous drainage of right upper pulmonary vein to right superior vena cava. Cardiac CT with axial reconstructed image (a) and sagittal reconstructed image (b) showing superior sinus venosus atrial septal defect (arrows) and right upper pul-

monary vein connecting to superior vena cava. SVC superior vena cava, RUPV right upper pulmonary vein, RA dilated right atrium, LA left atrium, RPA right pulmonary artery, MPA main pulmonary artery, AO ascending aorta, DAO descending aorta

and possibly the mitral or common AV valve), provide connections to the outflow tracts (via the infundibulum and outlet septum), and carry the atrioventricular conduction system. Defects are divided into four geographic regions which are defined by specific anatomic landmarks and features: central perimembranous defects, inlet defects, trabecular muscular defects, and outlet defects.

Central perimembranous defects are located below and behind the postero-inferior limb of the septal band, at the anteroseptal commissure behind the septal leaflet of the tricuspid valve, and below the aortic valve right commissure and non-coronary commissure [10]. These adjacent structures may be hemodynamically affected; patients with central perimembranous VSDs may have aneurysmal tricuspid valve tissue within

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and surrounding the defect, which may partially or completely obstruct the defect, minimizing the left to right shunt it creates. Aortic valve leaflets may also prolapse into the defect, leading to aortic insufficiency. These defects are also termed membranous, perimembranous, paramembranous, or infracristal VSDs. Inlet defects are within the inflow portion of the right ventricle along the septal leaflet of the tricuspid valve and located below the medial papillary muscle, postero-inferior limb of the septal band, and anteroseptal commissure of the tricuspid valve [10]. They are associated with AVSDs and (as may be the case with any type of VSD) may extend out further to the perimembranous, trabecular muscular, or outlet areas of the ventricular septum. Trabecular muscular defects are located within the apical muscular component of the ventricular septum and have complete muscular borders. Small trabecular muscular defects are commonly diagnosed, and many close spontaneously over time, but may be large, or have complex tunnel-like paths and shunts. Trabecular muscular VSDs can be further subdivided by their region of apical muscular septum: midseptal, apical (distal to moderator band), postero-­ inferior, and antero-superior (anterior to the septal band) [10]. Outlet defects are located in the outlet portion of the RV, between the limbs of the septal band and within, or just inferior to, the subpulmonary infundibulum (or conus). These types of defects may often be associated with malalignment of the infundibulum (or outlet septum) and the apical muscular septum but are not always associated with malalignment [10]. Outlet VSDs can be further subdivided into outlet perimembranous (Fig.  6.4), outlet muscular defects, and doubly committed juxta-arterial defects. Outlet perimembranous VSDs may be associated with malalignment of the infundibulum (or outlet septum); in contrast to central perimembranous VSDs, outlet perimembranous VSDs are adjacent to the septal leaflet of the tricuspid valve. Outlet muscular defects may also be associated with malalignment of the infundibulum. An outlet VSD with anterior malalignment (with ventricu-

loarterial concordance) is seen in tetralogy of Fallot and associated with subpulmonary outflow obstruction [10]. Posterior malalignment (with ventriculoarterial concordance) is typically associated with subaortic stenosis, aortic arch obstruction, or arch interruption. When the muscular infundibulum (outlet septum) is absent, there is fibrous continuity between the pulmonary and aortic valves, and the associated VSDs are doubly committed juxta-arterial defects (subarterial ventricular septal defect). Aortic valve leaflets may prolapse into these types of VSDs, leading to aortic insufficiency. A final, but rare, type of VSD is within the small area of the membranous septum which walls the RA from the LV; a defect here would cause a left to right shunt from the LV to RA, which when found as a congenital defect is termed a Gerbode defect [11]. In our experience, these may also be found after VSD repair or AVSD repair as a residual shunt and may possibly occur after other intracardiac procedures or insults.

Atrioventricular Septal Defects As described above regarding the formation of the atrial septum and ventricular septum, mesenchymal cells from the atrial septum primum and endocardial atrioventricular cushions form part of the central cardiac crux [8], and the endocardial cushions create the central areas of the ventricular septum, atrial septum, and atrioventricular valves. Developmental failure of the endocardial cushions to fuse results in a central defect in the atrial septum (primum defect), ventricular septum (inlet defect) [3], and abnormalities of the atrioventricular valves (common atrioventricular valve with one or multiple orifices or a trileaflet mitral valve with “cleft”)  – an atrioventricular septal defect (AVSD). AVSDs can be categorized in several ways [3]. Complete AVSDs are defined by a primum ASD, inlet VSD (typically large), and common AV valve with a common annulus (Fig.  6.5). The common AV valve leaflets can vary in number and size. Although uncommon, some patients with complete AVSDs have a closed ASD or VSD

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b MPA

RV AO

LV LA

LV RV

c

AO LA

LV RV

Fig. 6.4  A 5-month-old infant with anomalous aortic origin of right coronary artery and ventricular septal defect. Cardiac CT axial (a), coronal (b), and sagittal (c) recon-

structed images show perimembranous ventricular septal defect (arrows). LV left ventricle, RV right ventricle, LA left atrium, AO aortic root, MPA main pulmonary artery

component (which may be closed by aneurysmal AV valve tissue). Complete AVSDs may be balanced, where the atrial septum and common AV valve sit over the ventricular septum, and there is equal valve inflow distribution to the RV and LV, or unbalanced, when there is unequal AV valve commitment and inflow into either the RV or LV.  The ventricle receiving the less, unequal inflow is typically hypoplastic [3]. Transitional AVSDs differ from complete AVSDs by attachments of the AV valve tissue (specifically the superior bridging leaflet) to the ventricular septum, creating a smaller, restrictive

VSD orifice. This also creates two separate AV valve inflow orifices (to the RV and LV), despite anatomically being a single AV valve annulus. Physiologically, patients with this defect have predominant interatrial shunting and present with this clinical picture but may also have significant atrioventricular valve regurgitation. Primum AVSDs have a primum ASD but have no inlet VSD component and have variably been described to have two separate AV valve inflow orifices with an anatomically single AV valve annulus or two separately formed AV valves (right-sided and left-sided). They anatomically

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RV LV

RA

LA

Fig. 6.5  An infant with unbalanced (right ventricular dominant) atrioventricular septal defect. Cardiac CT was performed to evaluate aortic arch. Axial four-chamber reconstructed image shows primum atrial septal defect (white arrow) and inlet ventricular septal defect (black arrow). LV left ventricle, RV right ventricle, LA left atrium, RA right atrium

differ from fully formed tricuspid and mitral valves, and in particular the left AV valve has an apparent “cleft” in what would be the anterior mitral leaflet; the left AV valve actually has three separate leaflet components.

Diagnosis Echocardiography is the primary method of diagnosing ASDs, VSDs, and AVSDs. Often these are diagnosed in infancy but may be diagnosed at any point later in childhood or adulthood. Echocardiography, both with 2D imaging and Doppler evaluation, in particular useful for detecting borders and edges of the defects as well, demonstrates the direction and degree of shunting through the defects. Furthermore, echocardiography is well suited for evaluation of the AV valves, chordal attachments, presence of stenosis, or regurgitation. Contrast echocardiography using intravenous agitated saline can be used to visualize evidence of intracardiac shunts. A major limitation of echocardiography is inadequate visualization in patients with poor acoustic

windows, particularly of the atrial septum and systemic and pulmonary veins. Cardiac CT is most often utilized for evaluation of other congenital heart defects associated with ASDs, VSDs, or AVSDs such as coarctation of the aorta, pulmonary artery stenosis or hypoplasia, anomalous pulmonary venous connections, or coronary artery anomalies. However, as mentioned above ASDs and VSDs are the most common congenital heart defects and often co-­ exist with multiple congenital heart defects. Therefore, these defects should be suspected and evaluated for in patients undergoing cardiac imaging.

 atient Preparation, Contrast P Medium, and Cardiac CT Technique Prior to the exam, any prior cardiac evaluations and echocardiograms should be reviewed to help plan the CT examination. The usual total contrast dose is 1.5–2  ml/kg of body weight in young infants. In neonates, the contrast medium is usually administered by using dual-head power injector at injection rate of 0.8–1 ml/sec in a neonatal scan, followed by a saline bolus. Automated bolus tracking technique or visual monitoring with manual starting can be used after contrast injection. Average scan delay of 4 seconds is used to evaluate right-sided heart structures, and a scan delay of 5–8 seconds is used to evaluate left-­ sided heart structures. If a patient has an ASD or VSD, this should be taken in consideration  – contrast often shunts (usually temporarily) right to left and opacifies the left ventricle sooner than in normal cardiac anatomy, and therefore the scan delay time may need to be shortened. In patients with little cardiac motion and lower heart rates (optimal heart rates depend on individual patterns but are ideally 60  bpm or less), the atrial and ventricular septum are better visualized. For other patients with inadequate cardiac motion, we typically describe any ASDs or VSDs found but state that we cannot exclude a small ASD or small VSD – if needed, a complete echocardiogram can be done which has higher accuracy.

6  Septal Defects: Atrial Septal Defects, Ventricular Septal Defects, Atrioventricular Septal Defects…

The preferred cardiac CT technique is prospective gated cardiac CT using modern dual-­ source multidetector CT scanners. Retrospective gated approach is useful for evaluation of ventricular function and ventricular sizes, allows volumetric measurements, and also allows evaluation of ventricular function and wall motion. This may be used and of particular relevance for patients with hypoplastic ventricles and unbalanced AVSDs.

Management Approach ASDs were the first type of congenital heart defect to be repaired with open heart cardiac surgery in the 1950s [12] and was shortly followed by surgical VSD repair. For majority of VSDs and ASDs (including those not of the secundum ASD type), surgical closure is recommended. This can be accomplished with primary closure or patch closure. Since the 1990s, ASD closure via transcatheter device implantation has been described [13] and popularized, with increasing availability and choices of device types and sizes over time. Similarly, for certain select types and sizes of VSDs, transcatheter device closure has also been described [14] since the early 2000s; however, VSD device closure procedures are technically more challenging and not as widely performed. For children with large, hemodynamically significant VSDs and AVSDs, surgical repair is typically done at 4–6 months of age as the symptoms of high-output heart failure from the left to right shunt increase. This can be accomplished with primary closure or patch closure. AVSD repair may be performed with various techniques but accomplishes similar goals: closure of the ASD, VSD, and separation of the common AV valve (if present) into two functional valves with reduction of as much valve regurgitation or stenosis as possible. Conversely, children with ASDs may not develop symptoms depending on the degree of left to right shunting of the defect and may not be diagnosed until much later in childhood or even adulthood. When diagnosed in infancy, surgical

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repair is typically planned at 2–4 years of age but may be deferred until later age if the child is thought to be a suitable candidate for transcatheter device closure.

Outcome Patients with ASDs and VSDs in general have an excellent prognosis; small defects may spontaneously close over time without intervention. Larger ASDs and VSDs, when diagnosed appropriately in infancy and undergo closure as described above, have an excellent prognosis. However, a long-term follow-up study found slightly elevated overall risk of death in patients with simple defects (including but not exclusive to ASDs and VSDs) [15], suggesting that they are at risk of slightly worse clinical outcomes compared to healthy patients and warrant regular medical follow-up. Patients with AVSDs have overall good prognosis but may have residual cardiac lesions including residual ASDs (uncommon) or VSDs (common) [3], AV valve regurgitation, or AV valve stenosis. These may require repeat surgical intervention or AV valve replacement, and regular lifelong cardiology follow-up is recommended. Regardless, many patients enjoy overall good outcomes and quality of life.

References 1. Liu Y, Chen S, Zühlke L, et  al. Global birth prevalence of congenital heart defects 1970–2017: updated systematic review and meta-analysis of 260 studies. Int J Epidemiol. 2019;48(2):455–63. https://doi. org/10.1093/ije/dyz009. 2. Pierpont ME, Brueckner M, Chung WK, et al. Genetic basis for congenital heart disease: revisited: a scientific statement from the American Heart Association. Circulation. 2018;138(21):e653–711. https://doi. org/10.1161/CIR.0000000000000606. 3. Cohen MS.  Common atrioventricular canal defects. In: Echocardiography in pediatric and congenital heart disease. Wiley; 2009. p.  230–48. https://doi. org/10.1002/9781444306309.ch3. 4. Anderson RH, Brown NA, Webb S. Development and structure of the atrial septum. Heart. 2002;88(1):104– 10. https://doi.org/10.1136/heart.88.1.104.

62 5. Van Praagh S, Carrera ME, Sanders SP, Mayer JE, Van Praagh R.  Sinus venosus defects: unroofing of the right pulmonary veins  – anatomic and echocardiographic findings and surgical treatment. Am Heart J. 1994;128(2):365–79. https://doi. org/10.1016/0002-­8703(94)90491-­x. 6. Butts RJ, Crean AM, Hlavacek AM, et  al. Veno-­ venous bridges: the forerunners of the sinus venosus defect. Cardiol Young. 2011;21(6):623–30. https:// doi.org/10.1017/S1047951111000710. 7. Raghib G, Ruttenberg HD, Anderson RC, Amplatz K, Adams P, Edwards JE.  Termination of left superior vena cava in left atrium, atrial septal defect, and absence of coronary sinus. Circulation. 1965;31(6):906–18. https://doi.org/10.1161/01. CIR.31.6.906. 8. Forbus G, Shirali G. Anomalies of the ventricular septum. In: Echocardiography in pediatric and congenital heart disease. Wiley; 2009. p. 175–87. https://doi. org/10.1002/9781444306309.ch3. 9. Lamers WH, Moorman AFM. Cardiac septation. Circ Res. 2002;91(2):93–103. https://doi.org/10.1161/01. RES.0000027135.63141.89. 10. Lopez L, Houyel L, Colan SD, et  al. Classification of ventricular septal defects for the eleventh iteration of the international classification of diseases-striving for consensus: a report from the International Society for Nomenclature of Paediatric and Congenital Heart

M. D. Patel Disease. Ann Thorac Surg. 2018;106(5):1578–89. https://doi.org/10.1016/j.athoracsur.2018.06.020. 11. Gerbode F, Hultgren H, Melrose D, Osborn J.  Syndrome of left ventricular-right atrial shunt; successful surgical repair of defect in five cases, with observation of bradycardia on closure. Ann Surg. 1958;148(3):433–46. https://doi. org/10.1097/00000658-­195809000-­00012. 12. Cohn LH.  Fifty years of open-heart surgery. Circulation. 2003;107(17):2168–70. https://doi. org/10.1161/01.CIR.0000071746.50876.E2. 13. Hellenbrand WE, Fahey JT, McGowan FX, Weltin GG, Kleinman CS.  Transesophageal echocardiographic guidance of transcatheter closure of atrial septal defect. Am J Cardiol. 1990;66(2):207–13. https:// doi.org/10.1016/0002-­9149(90)90590-­w. 14. Hijazi ZM, Hakim F, Haweleh AA, et  al. Catheter closure of perimembranous ventricular septal defects using the new Amplatzer membranous VSD occluder: initial clinical experience. Catheter Cardiovasc Interv. 2002;56(4):508–15. https://doi.org/10.1002/ ccd.10292. 15. Diller G-P, Kempny A, Alonso-Gonzalez R, et  al. Survival prospects and circumstances of death in contemporary adult congenital heart disease patients under follow-up at a large tertiary centre. Circulation. 2015;132(22):2118–25. https://doi.org/10.1161/ CIRCULATIONAHA.115.017202.

7

Atrioventricular Valves: Tricuspid Valve Santosh C. Uppu

Introduction Tricuspid atresia is a form of cyanotic congenital heart disease where the tricuspid valve is absent; as a result, there is right to left shunting across the atrial septum. It is associated with hypoplastic right ventricle and surgery involving single ventricle pathway is undertaken in the current era. Failure of delamination of the tricuspid valve from the underlying myocardium results in Ebstein anomaly which is associated with apical displacement of the tricuspid annulus; it is a rare CHD with a prevalence of 0.44 per 100 live births [1]. Surgical repair is individualized based on the anatomic variation and associated lesions and can range from single ventricle to biventricular approaches.

Embryology Atrioventricular valve development starts following the fusion of the endocardial cushions around 35  days in the embryonic development. The

S. C. Uppu (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

valves that are destined to be future mitral and tricuspid valves are initially surrounded by mesenchymal tissue proliferation; as blood flows through this mesenchymal tissue, it gradually thins out on the ventricular surface developing into thin mobile leaflets. These valves are initially attached to the ventricular wall by muscular cords that later degenerate replacing the muscle with dense connective tissue that become lined by endocardium and evolve into chordae tendineae. The papillary muscles along with chordae tendineae function as tensile apparatus that play a crucial role in the competent tricuspid and mitral valves. The valves and the supporting structures develop by delamination of the inner layers of the endocardium [2]. The mature tricuspid valve is composed of three leaflets: anterior, inferior or posterior, and septal leaflets. The hallmark of the tricuspid valve is its septophilic nature with chordal insertion to the interventricular septum [3]. Mitral valve is composed of two leaflets that are oriented in an oblique fashion; as such there is an anterolateral and posteromedial commissure and it has chordal attachments to two dominant papillary muscles. Mitral valve is septophobic in comparison. The anterior leaflet is usually longer, dome shaped, and subdivided into A1-3 scallops, whereas the posterior leaflet is crescent shaped and subdivided into P1-3 scallops [4].

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Tricuspid Atresia

and might become smaller over time and thus warrant careful evaluation [3, 7, 8].

Tricuspid atresia is a form of cyanotic congenital heart disease with a prevalence of 1.17 per 100 live births and accounts for 1% of CHDs [1]. The tricuspid valve and the inflow portion of the right ventricle are absent; it is associated with right ventricular hypoplasia. The infundibular and trabecular portions are developed to a varying degree depending on the size of the ventricular septal defect. The venous flow entering the right atrium is directed across the obligatory atrial septal communication toward the left atrium [5]. Tricuspid atresia is further classified into three types (Table 7.1). With pulmonary atresia patent ductus arteriosus ensures pulmonary blood flow in the neonatal period and maintaining its patency by prostaglandin infusion is essential [6]. Associated lesions are dependent on the type of tricuspid atresia, and coarctation of the aorta is likely in type II tricuspid atresia with small VSD. Pulmonary atresia and stenosis are seen in both type I and II tricuspid atresia. Other associated lesions include right aortic arch, persistent left superior vena cava, left juxtaposition of the atrial appendages, etc. Cyanosis depends on the degree of pulmonary stenosis. Patients with large VSDs and unrestricted pulmonary blood flow present with pulmonary overcirculation. Type II tricuspid atresia with subaortic VSD obstruction might result in decreased systemic blood flow. The VSDs in tricuspid atresia have muscular rims

Table 7.1  Classification of tricuspid atresia Type I a b c Type II a b c Type III

Normally related great arteries No VSD and pulmonary atresia Small VSD and pulmonary stenosis Large VSD without pulmonary stenosis D-transposition of the great arteries VSD with pulmonary atresia VSD with pulmonary stenosis VSD without pulmonary stenosis Associated complex lesions (malposition, truncus, atrioventricular septal defect)

70– 80%

12– 20%

3%

Diagnosis Diagnosis is usually made either pre- or postnatally by echocardiography. The absent tricuspid valve and hypoplastic right ventricle are noticeable on echocardiogram and full anatomic details can be obtained. Presence of associated lesions can also be recognized by a thorough echocardiogram. There is a role for cross-sectional imaging especially with a cardiac CT in patients with pulmonary atresia and PDA-dependent pulmonary circulation as the cardiac CT helps better understand the branch pulmonary arteries. In the event that an interventional approach is planned in this subset, the CT images might help create a roadmap. Cardiac CT also helps understand those at risk for branch PA isolation who might benefit from surgical pulmonary angioplasty. Cardiac CT also better delineates associated vascular anomalies.  ardiac CT Technique and Patient C Preparation The patient preparation and sequence planning are discussed in the earlier chapters. Iso-osmolar, non-ionic, and water-soluble contrast agents are preferred. The usual total contrast dose is 1.5–2 ml/kg (maximum contrast dose of 150 ml in adults). The contrast medium is usually administered using a dual-head power injector. The injection rate is determined by the size of the intravenous (IV) catheter, and a rate of 0.8– 1.2 ml/sec chased by a saline bolus is appropriate for neonates with a 24G IV.  Automated bolus tracking technique or visual monitoring with manual triggering can be used after contrast injection. An average scan delay of 4  seconds from the trigger can be used but might need adjustment based on the heart rate. The site of peripheral IV placement needs to be tailored based on the structure of interest. Prospective EKG triggering techniques help lower the radiation dose. There is a role for cardiac CT to evaluate before or after subsequent surgical interventions. Patients with MRI-incompatible hardware (Pacemaker, devices, etc.) might be

7  Atrioventricular Valves: Tricuspid Valve

better candidates for cardiac CT.  Retrospective sequences can be utilized to obtain functional CT that can help estimate ventricular size and function. Imaging of the Fontan pathway is technically challenging due to unique Fontan hemodynamics and flow streaming patterns; inadequate contrast opacification of the Fontan pathway or branch pulmonary arteries by traditional pulmonary embolus CT protocols results in false-positive diagnosis of a thrombus or a non-diagnostic study. A biphasic CT angiography with a single-­ site injection via an adequate sized peripheral IV along with two acquisition phases that are about 60–70  seconds apart to visualize the entire systemic venous and pulmonary arterial pathways is ideal [9]. IV sizes greater than 22 g are better for contrast injection in Fontan patients.

Management Managing tricuspid atresia needs a tailored approach based on the anatomy, physiology, and ultimate surgical plan. Patients with reduced pulmonary blood flow need a reliable pulmonary circulation which can be achieved either by a shunt in a neonate or Glenn anastomosis in an older infant. Those with pulmonary overcirculation might benefit from either PA banding or earlier Glenn anastomosis. It is important to ensure a protected pulmonary vascular bed as the ultimate surgical goal is a successful Fontan operation. Those with systemic outflow obstruction might benefit from Damus-Kaye-Stansel anastomosis as part of the initial repair [10]. The urgical approach for tricuspid atresia evolved over time from a palliative procedure to control pulmonary overcirculation to Fontan and colleagues describing a way to separate pulmonary and systemic venous return in 1971 [11]. The original Fontan and Baudet procedure involved classic Glenn anastomosis directing superior vena cava flow to the right lung, redirecting inferior vena cava flow to the pulmonary artery with a valved connection between the right atrium and pulmonary artery, valve insertion in the inferior vena cava-right atrial junction, atrial septal communication closure, and eliminating the pulmonary artery-right ventricular connection [11]. The Fontan proce-

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dure evolved many times over the next 50 years and has become a standard procedure for various single ventricular lesions that are otherwise lethal. Prerequisites for a successful Fontan procedure include unobstructed pulmonary arteries, normal pulmonary arterial vascular resistance, good left ventricular function, and well-­ functioning mitral valve.

Outcome The overall outcomes for tricuspid atresia have improved over time. Survival after the Fontan procedure for TA has been reported as 90% at the age of 1 month, 81% at 1 year, 70% at 10 years, and 60% at 20 years [12]. The estimation of long-­ term outcomes of Fontan population spans up to 35  years, with the ANZFR (Australia and New Zealand Fontan Registry) reporting a 62% survival over that time frame [13, 14]. Older Fontan techniques have worse long-term outcomes and have been falling out of favor for newer modifications. Fontan pathway has its inherent limitations stemming from the lack of subpulmonary pump; this along with unique Fontan hemodynamics results in elevated systemic venous pressure and reduced cardiac output which results in chronic morbidity associated with this circulation [14].

Ebstein Anomaly Ebstein anomaly is a rare congenital heart defect with a prevalence of 0.44 per 100 live births and accounts for ~0.5% of CHDs [1]. Ebstein anomaly results from failure of delamination of the tricuspid valve from the underlying myocardium; as a result the hinge points of the septal and posterior tricuspid leaflets are displaced apically resulting in atrialization of the right ventricle (Fig. 7.1). The functional orifice is rotated anteriorly and toward the pulmonary valve, and the apical displacement of the septal leaflet from the true annulus can be measured on echocardiography and is reported as displacement index [15]. The tricuspid leaflets may have adhesions below the pulmonary valve, and tricuspid valve coaptation defects are common resulting in significant regurgita-

S. C. Uppu

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FRV LV RA

ARV

LA

Fig. 7.1  Infant with Ebstein anomaly of tricuspid valve and severe apical displacement of septal leaflet of tricuspid valve (arrows) with significantly atrialized right ventricle. ARV atrialized right ventricle, FRV functional right ventricle, RA right atrium, LV left atrium

tion. It is believed that Ebstein anomaly is not just an isolated tricuspid valve disease but a global myocardial pathology that manifest as anatomic and physiologic problems encountered in these patients [3]. The natural history varies with the degree of tricuspid displacement, resultant right ventricular size, underlying myocardial and conduction abnormalities, and presence of an atrial septal communication. Severe Ebstein patients present early with significant cyanosis, cardiomegaly, and heart failure and are often difficult to manage in the neonatal period due to elevated pulmonary vascular resistance. Milder forms of Ebstein anomaly go undiagnosed for long periods and might come to medical attention for milder symptoms like palpitations, dyspnea with exertion, exercise intolerance, etc. [15]. Associated anomalies include right ventricular outflow tract obstruction, pulmonary stenosis, pulmonary regurgitation, ventricular dysfunction, mitral valve abnormalities, patent foramen ovale or an atrial septal communication, and Wolff-Parkinson-White syndrome [15, 16].

Diagnosis Ebstein anomaly is diagnosed based on the severity of the lesion either in utero or postnatally and various ages. Severe lesions with hemodynamic compromise come to medical attention early. Chest x-ray may show cardiomegaly, and a routine EKG may show pre-excitation that brings them to medical attention in mild asymptomatic patients. Echocardiography is still a standard imaging modality to diagnose Ebstein anomaly. Displacement index value greater than 8 mm/m2 helps with the diagnosis. Severity of neonatal Ebstein anomaly can be predicted by using Great Ormond Street Echocardiography (GOSE score) index >1 [17]. Similar scores have been proposed for in-utero Ebstein anomaly diagnosis [18, 19]. Fetuses or neonates with severe pulmonary regurgitation are at high risk due to circular shunt physiology [20]. Cross-sectional imaging with cardiac MRI or cardiac CT has a potential role in those with suboptimal echocardiographic windows and in those where better delineation of the tricuspid valve is required for planning surgical intervention such as cone procedure. Patients with MRI-incompatible hardware or those with claustrophobia or those requiring anesthesia might be better candidates for cardiac CT due to short scan times. Cardiac CT also helps better delineate associated lesions and extracardiac structures [21, 22].  ardiac CT Technique and Patient C Preparation Patient preparation and CT sequence planning are discussed in the earlier chapters. Iso-osmolar, non-ionic, and water-soluble contrast agents are preferred. Imaging of the tricuspid valve is better achieved by triphasic injection protocols, as these allow visualizing both right and left heart chambers. CT protocols might be modified based on the structure of interest and to reduce the contrast or radiation dose. It is important to check renal function parameters and hydration status prior to contrast administration. Protocols that minimize contrast streak artifacts will help visualize the right atrium better. Cardiac CT in neonates might help better evaluate the nature of pulmonary atresia (functional or anatomic) in

7  Atrioventricular Valves: Tricuspid Valve

those presenting with cyanosis. The injection rate is determined by the size of the intravenous (IV) catheter, and a rate of 0.8–1.2 ml/sec chased by a saline bolus is appropriate for neonates with a 24G IV.  Automated bolus tracking technique or visual monitoring with manual triggering can be used after contrast injection. An average scan delay of 4 seconds from the trigger can be used but might need adjustment based on the heart rate. The site of peripheral IV placement needs to be tailored based on the structure of interest. Prospective EKG triggering techniques help lower the radiation dose. Severe Ebstein anomaly destined for single ventricle palliation might require cardiac CT to guide surgical interventions. Imaging of the Fontan pathway is described in the early sections. Retrospective gating sequences can be utilized to estimate right ventricular size.

Management Neonates with cyanosis need prostaglandin to ensure adequate pulmonary blood flow; inhaled nitric oxide is also utilized if the pulmonary vascular resistance is elevated. Those requiring neonatal surgery are at higher risk. Surgical techniques evolved over time; right ventricular exclusion and systemic to pulmonary artery shunt (Starnes procedure) has been described for neonates presenting with cyanosis. This procedure along with its modifications reported 70% survival in otherwise near-fatal disease [23, 24]. Neonatal biventricular repair involves tricuspid valve repair using anterior leaflet, right atrial reduction, fenestrated ASD closure, and repair of associated defects that reported similar early survival rates [25]. Neonates with significant cardiomyopathy or inadequate ventricles might be transplant candidates. Children and adults with cardiomegaly and decreased exercise tolerance might benefit from surgical repair. Cone repair of the tricuspid valve is now considered an ideal procedure and good outcomes have been shown since its origin [26, 27]. Tricuspid valve replacement might be considered in those where the repair is not feasible, but it comes with its own set of problems. Glenn anastomosis is considered along with tricuspid valve repair when the repaired tricuspid valve is

67 Table 7.2 Great Ormond Street Echocardiography (GOSE) score and infantile mortality GOSE score 1 2 3 4

Mortality (%) 0 10 44 100

deemed not adequate to accommodate the entire systemic venous return; this results in a pulsatile Glenn circulation.

Outcomes Fetal or neonatal presentation of Ebstein anomaly has uniform poor prognosis probably related to underdeveloped lungs (Table 7.2) [3, 17, 28]. Current surgical techniques both univentricular and biventricular approaches have shown improved neonatal survival [23, 25]. Outcomes of late surgical repair and replacement have been good. The 20-year survival is ~70%. Predictors of early mortality include moderate right ventricular dysfunction. Mitral regurgitation and left ventricular dysfunction are associated with late poor outcomes. Given the underlying cardiomyopathy component, patients tend to experience arrhythmias and ventricular dysfunction that affects the quality of life [29]. GOSE score  =  (RA  +  atrialized RV) ÷ (RV + LA + LV). Grade 1 ≤ 0.5, Grade 2 = 0.5– 0.99, Grade 3 = 1.1–1.49, and Grade 4 ≥ 1.5

References 1. Liu Y, Chen S, Zühlke L, Black GC, Choy M-K, Li N, et  al. Global birth prevalence of congenital heart defects 1970-2017: updated systematic review and meta-analysis of 260 studies. Int J Epidemiol. 2019;48:455–63. https://doi.org/10.1093/ije/dyz009. 2. Sadler TW. Langman’s medical embryology. 12th ed. Philadelphia: Lippincott Williams & Wilkins; 2011. 3. Cetta F, Dearani JA, O’Leary PW, Driscoll DJ. Tricuspid valve disorders: atresia, dysplasia, and ebstein anomaly. In: Allen HD, Shaddy RE, Penny DJ, Feltes TF, Cetta F, editors. Moss and Adams’ heart disease in infants, children, and adolescents: including the fetus and young adult. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2016. p. 949–81. 4. Dal-Bianco JP, Levine RA.  Anatomy of the mitral valve apparatus: role of 2D and 3D ­echocardiography.

68 Cardiol Clin. 2013;31:151–64. https://doi. org/10.1016/j.ccl.2013.03.001. 5. Rao PS.  Tricuspid atresia. Curr Treat Options Cardiovasc Med. 2000;2:507–20. https://doi. org/10.1007/s11936-­000-­0046-­6. 6. Rao PS.  A unified classification for tricuspid atresia. Am Heart J. 1980;99:799–804. https://doi. org/10.1016/0002-­8703(80)90632-­8. 7. Sanders SP.  Hearts with functionally one ventricle. In: Lai WW, Mertens LL, Cohen MS, Geva T, editors. Echocardiography in pediatric and congenital heart disease: from fetus to adult. Oxford: Wiley; 2016. p. 511–40. 8. Rao PS. Subaortic obstruction after pulmonary artery banding in patients with tricuspid atresia and double-­ inlet left ventricle and ventriculoarterial discordance. J Am Coll Cardiol. 1991;18:1585–6. https://doi. org/10.1016/0735-­1097(91)90695-­6. 9. Boggs R, Dibert T, Co-Vu J, DeGroff C, Quinn N, Chandran A.  Optimized computed tomography angiography protocol for the evaluation of thrombus in patients with Fontan anatomy. Pediatr Cardiol. 2020;41:1601–7. https://doi.org/10.1007/ s00246-­020-­02417-­9. 10. Neches WH, Park SC, Lenox CC, Zuberbuhler JR, Bahnson HT.  Tricuspid atresia with transposition of the great arteries and closing ventricular septal defect. Successful palliation by banding of the pulmonary artery and creation of an aorticopulmonary window. J Thorac Cardiovasc Surg. 1973;65:538–42. 11. Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax. 1971;26:240–8. https://doi.org/10.1136/ thx.26.3.240. 12. Sittiwangkul R, Azakie A, Van Arsdell GS, Williams WG, McCrindle BW.  Outcomes of tricuspid atresia in the Fontan era. Ann Thorac Surg. 2004;77:889–94. https://doi.org/10.1016/j.athoracsur.2003.09.027. 13. Australia and New Zealand Fontan Registry: REPORT 2018. 2019. 14. Rychik J, Atz AM, Celermajer DS, Deal BJ, Gatzoulis MA, Gewillig MH, et al. Evaluation and management of the child and adult with fontan circulation: a scientific statement from the American Heart Association. Circulation. 2019:CIR0000000000000696. https:// doi.org/10.1161/CIR.0000000000000696. 15. Cetta F, Eidem BW.  Ebstein anomaly, tricuspid valve dysplasia, and right atrial anomalies. In: Lai WW, Mertens LL, Cohen MS, Geva T, editors. Echocardiography in pediatric and congenital heart disease: from fetus to adult. Oxford: Wiley; 2016. p.  231–42. https://doi.org/10.1002/9781118742440. ch13. 16. Keane JF, Fyler DC.  Tricuspid valve problems. In: Keane JF, Lock JE, Fyler DC, editors. Nadas’ pediatric cardiology. second. Philadelphia: Saunders; 2006. 17. Celermajer DS, Cullen S, Sullivan ID, Spiegelhalter DJ, Wyse RK, Deanfield JE.  Outcome in neonates with Ebstein’s anomaly. J Am Coll Cardiol. 1992;19:1041–6.

S. C. Uppu 18. Celermajer DS, Bull C, Till JA, Cullen S, Vassillikos VP, Sullivan ID, et  al. Ebstein’s anomaly: presentation and outcome from fetus to adult. J Am Coll Cardiol. 1994;23:170–6. https://doi. org/10.1016/0735-­1097(94)90516-­9. 19. Torigoe F, Ishida H, Ishii Y, Ishii R, Narita J, Kawazu Y, et  al. Fetal echocardiographic prediction score for perinatal mortality in tricuspid valve dysplasia and Ebstein’s anomaly. Ultrasound Obstet Gynecol. 2020;55:226–32. https://doi.org/10.1002/uog.20302. 20. Freud LR, Escobar-Diaz MC, Kalish BT, Komarlu R, Puchalski MD, Jaeggi ET, et  al. Outcomes and predictors of perinatal mortality in fetuses with ebstein anomaly or tricuspid valve dysplasia in the current era: a multicenter study. Circulation. 2015;132:481–9. https://doi.org/10.1161/ CIRCULATIONAHA.115.015839. 21. Aggarwala G, Thompson B, van Beek E, Jagasia D.  Multislice computed tomography angiography of Ebstein anomaly and anomalous coronary artery. J Cardiovasc Comput Tomogr. 2007;1:168–9. https:// doi.org/10.1016/j.jcct.2007.08.004. 22. Zikria JF, Dillon EH, Epstein NF. Common CTA features of Ebstein anomaly in a middle-aged woman with a heart murmur and dyspnea on exertion. J Cardiovasc Comput Tomogr. 2012;6:431–2. https:// doi.org/10.1016/j.jcct.2012.04.012. 23. Starnes VA, Pitlick PT, Bernstein D, Griffin ML, Choy M, Shumway NE.  Ebstein’s anomaly appearing in the neonate. A new surgical approach. J Thorac Cardiovasc Surg. 1991;101:1082–7. 24. Sano S, Ishino K, Kawada M, Kasahara S, Kohmoto T, Takeuchi M, et  al. Total right ventricular exclusion procedure: an operation for isolated congestive right ventricular failure. J Thorac Cardiovasc Surg. 2002;123:640–7. https://doi.org/10.1067/ mtc.2002.121160. 25. Kumar TKS, Boston US, Knott-Craig CJ.  Neonatal Ebstein anomaly. Semin Thorac Cardiovasc Surg. 2017;29:331–7. https://doi.org/10.1053/j. semtcvs.2017.09.006. 26. da Silva JP, Baumgratz JF, da Fonseca L, Franchi SM, Lopes LM, Tavares GMP, et al. The cone reconstruction of the tricuspid valve in Ebstein’s anomaly. The operation: early and midterm results. J Thorac Cardiovasc Surg. 2007;133:215–23. https://doi. org/10.1016/j.jtcvs.2006.09.018. 27. Anderson HN, Dearani JA, Said SM, Norris MD, Pundi KN, Miller AR, et  al. Cone reconstruction in children with Ebstein anomaly: the Mayo Clinic experience. Congenit Heart Dis. 2014;9:266–71. https:// doi.org/10.1111/chd.12155. 28. Knott-Craig CJ, Goldberg SP. Management of neonatal Ebstein’s anomaly. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2007:112–6. https://doi. org/10.1053/j.pcsu.2007.01.008. 29. Dearani JA, Mora BN, Nelson TJ, Haile DT, O’Leary PW.  Ebstein anomaly review: what’s now, what’s next? Expert Rev Cardiovasc Ther. 2015;13:1101–9. https://doi.org/10.1586/14779072.2015.1087849.

8

Atrioventricular Valves: Congenital Mitral Valve Abnormalities Santosh C. Uppu

Introduction

Embryology

Isolated congenital mitral valve anomalies are rare; it is difficult to know the true incidence as congenital and acquired mitral lesions are usually accounted for together [1, 2]. A recent systematic review has reported the prevalence of mitral insufficiency as 1.5 per 100 live births accounting for 1.3% of all congenital heart defects (CHD), whereas the prevalence of mitral stenosis is reported at 0.8 per 100 live births representing 0.9% of CHD [3]. This systematic review does not differentiate isolated and associated lesions. Mitral valve disease is often part of a spectrum of left-sided obstructive lesions such as aortic stenosis, hypoplastic aorta, and coarctation of the aorta. Pediatric mitral valve diseases associated with connective tissue disorders, storage disorders, and cardiomyopathies will not be discussed in this chapter; other mitral abnormalities are discussed throughout this book.

Atrioventricular valve development starts following the fusion of the endocardial cushions around 35 days in the embryonic development following heart looping. Future mitral and tricuspid valves are initially surrounded by mesenchymal tissue proliferation; as blood flows through this mesenchymal tissue, it gradually thins out on the ventricular surface developing into thin mobile leaflets. These valves are initially attached to the ventricular wall by muscular chords that later evolve into chordae tendineae [4]. The papillary muscles along with chordae tendineae function as tensile apparatus that play a crucial role in the competent mitral valve [5]. The mature mitral valve is composed of two leaflets that are oriented in an oblique fashion; as such there are anterolateral and posteromedial commissures and it has chordal attachments to two dominant papillary muscles [6, 7]. Mitral valve and its support structures have a complex three-dimensional structure with a non-planar saddle shape. The anterior leaflet is usually longer, dome shaped, and subdivided into A1-3 scallops; it is in fibrous continuity with the noncoronary cusp of the aortic valve. The posterior leaflet is crescent shaped and subdivided into P1-3 scallops [1, 4, 8]. Congenital mitral valve anomalies result from abnormal mitral valve development; as such incomplete fusion of the ventricular aspect of superior and inferior

S. C. Uppu (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_8

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e­ndocardial cushions results in isolated mitral valve cleft. Abnormal development of the papillary muscles contributes to parachute mitral valve. Excessive shortening of chordae tendineae results in mitral arcade [9]. Reduced flow across the abnormal mitral valve during embryologic development results in hypoplastic downstream chambers and structures and thus might help understand the common spectrum of left-sided obstructive lesions [10, 11].

Supravalvular Mitral Ring This is a part of congenital mitral stenosis, where a thin membrane is closely adherent to the atrial aspect of the mitral valve. This membrane may be complete and circumferential acting as a diaphragm resulting in obstruction of the left atrial flow due to leaflet restriction, or it can be partial where it is not circumferential and results in lesser degree of stenosis. It is differentiated from cor-triatriatum sinister by proximity of the membrane to the mitral annulus. Supravalvular mitral ring is a part of Shone’s complex; other features include parachute mitral valve, subaortic stenosis, and coarctation of the aorta [9, 12].

Parachute Mitral Valve Normal mitral valve has chordal attachments to two dominant anterolateral and posteromedial papillary muscles. In a parachute mitral valve, the chordae attach to one papillary muscle. Variants of parachute mitral valve have been described where the chordae attach mostly to one dominant papillary muscle with some attachments to rudimentary papillary muscles [13]. Physiologically both these varieties are associated with restricted mitral valve opening resulting from reduced orifice, and mitral stenosis can be progressive during infancy [14]. Thickened chordae tendineae, mitral leaflets, and papillary muscles have been described with a parachute mitral valve. As mentioned above it can be a part of Shone’s complex [15–17].

Mitral Valve Dysplasia Isolated mitral valve stenosis results from dysplastic or hypoplastic mitral valve structures and is associated with a functioning left ventricle. The leaflets are thickened and rolled, chordae are shortened, and the papillary muscles are abnormal; it is usually associated with stenosis but regurgitation has also been reported [1, 6]. Dysplasia of individual leaflets has been described that is often associated with poor mitral valve coaptation and regurgitation.

Isolated Cleft Mitral Valve Isolated cleft mitral valve is a defect within the anterior mitral valve leaflet resulting in poor coaptation and mitral regurgitation. The cleft might be incomplete if the defect is within the leaflet tips. Isolated cleft mitral valves are distinct from the atrioventricular canal defect where the cleft attachments are directed toward the ventricular septum and are horizontal. In isolated cleft mitral valve, the cleft attachments are directed toward the membranous septum being vertical and are at risk for outflow obstruction, along with normal ventricular inflow/outflow ratio. Isolated cleft mitral valves can be associated with conotruncal anomalies, ventricular septal defect, double-inlet left ventricle, etc. [9, 10, 18].

Mitral Arcade or Hammock This is a rare anomaly that results due to muscularized short chordae tendineae, papillary muscles, and leaflets; as such it is difficult to differentiate between these structures. The mitral valve leaflet function is abnormal due to reduced interchordal space and poor coaptation resulting in regurgitation and some degree of stenosis. Presentation is dependent on the degree of mitral dysfunction with severe forms presenting in perinatal period and milder forms incidentally diagnosed [7].

8  Atrioventricular Valves: Congenital Mitral Valve Abnormalities

Double Orifice Mitral Valve This is a rare anomaly where there are two mitral orifices. There is a single mitral annulus with two openings that have their own tensor apparatus. Incomplete form of double orifice mitral valve results when a tissue connects the anterior and posterior leaflets resulting in two orifices. The orifices are usually of unequal size, and the size of the papillary muscles is related directly to the size of the opening. Many patients are asymptomatic and are incidentally diagnosed. Mitral regurgitation is common in about 50% and stenosis is reported in 13%. This anomaly is usually associated with atrioventricular canal defects or left-sided obstructive lesions [7, 9, 19, 20].

Congenital Mitral Valve Prolapse Mitral valve prolapse is rarely seen in the pediatric age group and is often associated with connective tissue disorders such as Marfan or Ehlers-Danlos syndrome. It results from myxoid degeneration of the valve leaflet along with annular dilatation; these changes happen over years and rarely present in the perinatal period. Reports of perinatal mitral valve prolapse have been described with mucopolysaccharidosis type VI presenting with severe mitral regurgitation and congestive heart failure in utero [21]. Similar findings have been described in neonatal Marfan syndrome [22, 23].

Diagnosis Evaluation of the mitral valve using transthoracic and transesophageal echocardiography provides excellent details and understanding

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into the mitral valve function as it provides hemodynamic information as well. Threedimensional echocardiography has made tremendous advances and is considered the reference standard for the mitral valve evaluation [9]. Careful detail to attention and methodical evaluation will help understand the disease and management planning. It is important to evaluate for the presence of associated lesions. There is a limited role for cardiac MRI or cardiac CT in evaluation of mitral valve anomalies. Cardiac CT is usually performed to evaluate associated lesions (Fig. 8.1).

Management Management of the congenital mitral valve anomalies is individualized based on the encountered anatomic variations. Medical management of mild-moderate mitral stenosis and regurgitation is recommended if hemodynamically feasible [16]. Patients with severe mitral stenosis that cannot be medically managed might benefit from either surgical or catheterization-based interventions, although one has to be cognizant of the possibility of developing mitral regurgitation as an unwanted consequence. Repair of the valves is challenging in younger patients due to the heterogeneity of lesions and high likelihood of recurrence [24]. Replacement of the valves in younger patients is also not ideal due to smaller valve size, lack of availability of prostheses, and patient growth. Surgical management for mitral valve regurgitation depends on the underlying anatomy and associated lesions, and mitral cleft repair has excellent surgical outcomes and is recommended as the primary intervention. Mitral valve replacement is only reserved for severe cases where the repair is not possible [1].

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b

a

RV RA LV

LA LA

LV

c

d

ARCH AO LA DAO

LV

e

DAO

Fig. 8.1  Nine-month-old infant with Shone’s complex, mitral valve stenosis, and hypoplastic aortic arch after surgical repair. Cardiac CT two-chamber (a), four-chamber, (b) and three-chamber (c) reconstructed images show thickened mitral valve (white arrows) and dilated left atrium. Parasagittal reconstructed image of aortic arch (d)

and three-dimensional volume-rendered reconstruction (e) show patent repaired aortic arch. LA left atrium, LV left ventricle, RA right atrium, RV right ventricle, AO aortic root, DAO descending thoracic aorta, ARCH aortic arch

8  Atrioventricular Valves: Congenital Mitral Valve Abnormalities

References 1. Mackie A, Smallhorn J.  Anatomical and functional mitral valve abnormalities in the pediatric population. In: Allen HD, Shaddy RE, Penny DJ, Feltes TF, Cetta F, editors. Moss and Adams’ heart disease in infants, children, and adolescents: including the fetus and young adult. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2016. p. 1065–84. 2. Colen T, Smallhorn JF.  Three-dimensional echocardiography for the assessment of atrioventricular valves in congenital heart disease: past, present and future. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2015;18:62–71. https://doi.org/10.1053/j. pcsu.2015.01.003. 3. Liu Y, Chen S, Zühlke L, Black GC, Choy M-K, Li N, et  al. Global birth prevalence of congenital heart defects 1970-2017: updated systematic review and meta-analysis of 260 studies. Int J Epidemiol. 2019;48:455–63. https://doi.org/10.1093/ije/dyz009. 4. Levine RA, Hagége AA, Judge DP, Padala M, Dal-Bianco JP, Aikawa E, et  al. Mitral valve disease--morphology and mechanisms. Nat Rev Cardiol. 2015;12:689–710. https://doi.org/10.1038/ nrcardio.2015.161. 5. Sadler TW. Langman’s medical embryology. 12th ed. Philadelphia: Lippincott Williams & Wilkins; 2011. 6. Ruckman RN, Van Praagh R. Anatomic types of congenital mitral stenosis: report of 49 autopsy cases with consideration of diagnosis and surgical implications. Am J Cardiol. 1978;42:592–601. https://doi. org/10.1016/0002-­9149(78)90629-­x. 7. Séguéla P-E, Houyel L, Acar P.  Congenital malformations of the mitral valve. Arch Cardiovasc Dis. 2011;104:465–79. https://doi.org/10.1016/j. acvd.2011.06.004. 8. Dal-Bianco JP, Levine RA.  Anatomy of the mitral valve apparatus: role of 2D and 3D echocardiography. Cardiol Clin. 2013;31:151–64. https://doi. org/10.1016/j.ccl.2013.03.001. 9. Kutty S, Colen TM, Smallhorn JF. Three-dimensional echocardiography in the assessment of congenital mitral valve disease. J Am Soc Echocardiogr. 2014;27:142–54. https://doi.org/10.1016/j. echo.2013.11.011. 10. Nielsen JC, Panesar LE.  Mitral valve and left atrial anomalies. In: Lai WW, Mertens LL, Cohen MS, Geva T, editors. Echocardiography in pediatric and congenital heart disease: from fetus to adult. Oxford: Wiley; 2016. p.  243–58. https://doi. org/10.1002/9781118742440.ch14. 11. Rogers L, Rychik J. Aortic Stenosis and Mitral Valve Dysplasia Syndrome. Fetal cardiovascular imaging a disease-based approach. Philadelphia: Elsevier/ Saunders; 2012. p. 253–63. 12. Shone JD, Sellers RD, Anderson RC, Adams P, Lillehei CW, Edwards JE.  The developmental com-

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plex of “parachute mitral valve,” supravalvular ring of left atrium, subaortic stenosis, and coarctation of aorta. Am J Cardiol. 1963;11:714–25. https://doi. org/10.1016/0002-­9149(63)90098-­5. 13. Hakim FA, Kendall CB, Alharthi M, Mancina JC, Tajik JA, Mookadam F.  Parachute mitral valve in adults-a systematic overview. Echocardiography. 2010;27:581–6. https://doi. org/10.1111/j.1540-­8175.2009.01143.x. 14. Toscano A, Pasquini L, Iacobelli R, Di Donato RM, Raimondi F, Carotti A, et al. Congenital supravalvar mitral ring: an underestimated anomaly. J Thorac Cardiovasc Surg. 2009;137:538–42. https://doi. org/10.1016/j.jtcvs.2008.08.023. 15. Mazur W, Siegel MJ, Miszalski-Jamka T, Pelberg R.  Atrioventricular Valve Abnormalities. CT atlas of adult congenital heart disease. London: Springer; 2013. p.  111–20. https://doi. org/10.1007/978-­1-­4471-­5088-­6_12. 16. Geggel RL, Fyler DC.  Mitral valve and left atrial lesions. In: Keane JF, Lock JE, Fyler DC, editors. Nadas’ pediatric cardiology. Second. Philadelphia: Saunders; 2006. 17. Davachi F, Moller JH, Edwards JE.  Diseases of the mitral valve in infancy. An anatomic analysis of 55 cases. Circulation. 1971;43:565–79. https://doi. org/10.1161/01.cir.43.4.565. 18. Van Praagh S, Porras D, Oppido G, Geva T, Van Praagh R. Cleft mitral valve without ostium primum defect: anatomic data and surgical considerations based on 41 cases. Ann Thorac Surg. 2003;75:1752– 62. https://doi.org/10.1016/s0003-­4975(03)00167-­x. 19. Warnes C, Somerville J.  Double mitral valve orifice in atrioventricular defects. Br Heart J. 1983;49:59–64. https://doi.org/10.1136/hrt.49.1.59. 20. Vainrib AF, Loulmet DF, Williams MR, Saric M.  Tale of 2 orifices. Circ Cardiovasc Imaging. 2019;12:e008372. https://doi.org/10.1161/ CIRCIMAGING.118.008372. 21. Honjo RS, Vaca ECN, Leal GN, Abellan DM, Ikari NM, Jatene MB, et  al. Mucopolysaccharidosis type VI: case report with first neonatal presentation with ascites fetalis and rapidly progressive cardiac manifestation. BMC Med Genet. 2020;21:37. https://doi. org/10.1186/s12881-­020-­0972-­y. 22. Tognato E, Perona A, Aronica A, Bertola A, Cimminelli L, De Vecchi S, et  al. Neonatal Marfan syndrome. Am J Perinatol. 2019;36:S74–6. https:// doi.org/10.1055/s-­0039-­1691770. 23. Abdel-Massih T, Goldenberg A, Vouhé P, Iserin F, Acar P, Villain E, et al. Marfan syndrome in the newborn and infants less than 4 months: a series of 9 patients. Arch Mal Coeur Vaiss. 2002;95:469–72. 24. Baird CW, Marx GR, Borisuk M, Emani S, del Nido PJ. Review of congenital mitral valve stenosis: analysis, repair techniques and outcomes. Cardiovasc Eng Technol. 2015;6:167–73. https://doi.org/10.1007/ s13239-­015-­0223-­0.

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Atrioventricular Connections: Double-Inlet Ventricle, Atrioventricular Discordance, and Congenitally Corrected Transposition of Great Arteries Rami Kharouf and Dilachew A. Adebo

Congenitally Corrected Transposition of Great Arteries Introduction Congenitally corrected transposition of great arteries, also known as Levo-looped transposition of the great arteries (L-TGA), is a rare form of congenital heart disease. It is characterized by atrioventricular and ventriculoarterial discordance (double discordance). It accounts less than 1% of congenital heart defects [1–3]. The cause of congenitally corrected transposition is multifactorial [4–8]. Isolated congenitally corrected transposition does not present with cyanosis since it is physiologically corrected as its name implies [4, 5]. These patients are at high risk for heart failure at adult life due to systemic right ventricular dysfunction. The morphologic right ventricle is not well suited to perform the workload of the systemic ventricle over a normal lifespan. As a result, systemic ventricular failure is a common late complication in congenitally corrected transR. Kharouf · D. A. Adebo (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]; [email protected]

position patients including those without associated cardiac lesions. Right ventricular dysfunction is thought to be due to an unfavorable tripartite geometric configuration that does not adapt to pressure or volume overload [9]. The long-term systemic workload results in progressive tricuspid regurgitation that increases volume overload and contributes to ventricular dysfunction and failure [10]. It is also proposed that the single coronary arterial supply to the morphologic right ventricle may increase the vulnerability of this ventricle to ischemia, particularly when hypertrophy is present [11]. Complete heart block is the most common arrhythmia in patients with congenitally corrected transposition of great arteries with signs and symptoms of bradycardia, fatigue, and poor exercise tolerance. In these patients, the cardiac conduction system is often abnormal and unstable.

Anatomy and Embryology There is abnormal looping of the primitive heart tube to the left which leads to abnormal positioning of the ventricles and to abnormal connections among atrial, ventricular, and arterial segments of the heart. The looping of the straight heart tube during the 3rd week of gestation is one of the key embryologic processes for correct anatomic alignment of the four chambers of the heart. Normally, the primitive heart tube loops to the

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_9

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right, resulting in the normal morphologic position of the right ventricle to the right of the left ventricle. However, in congenitally corrected transposition, morphologic left ventricle is positioned to the right of the morphologic right ventricle, and there is atrioventricular and ventriculoarterial discordance (Fig. 9.1a–c). Dextrocardia and situs inversus are some of the much less common variants of a congenitally corrected transposition of great arteries (Fig. 9.1). Although the anatomy of this lesion is different, the pathophysiology is the same. Coronary artery anatomy is variable in patients with congenitally corrected transposition. In general, the usual distribution represents a mirror image of normal anatomy with the origins of the

a

coronary arteries arising from the posterior facing sinuses due to the anterior positioning of the aortic valve. The vessel originating from the right-sided sinus is considered the morphologic left coronary artery with a circumflex and anterior descending branch, while the vessel originating from the left-facing sinus would have the epicardial distribution of a morphologic right coronary artery.

Diagnosis The diagnosis of congenitally corrected transposition is generally made by echocardiography. Most patients (>90%) have additional associated

b LV RA

MPA

RV AO LA

c

AO

RV

MPA

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Fig. 9.1  An infant with dextrocardia and congenitally corrected transposition of great arteries. Cardiac CT axial reconstructed images (a, b) and volume rendered reconstruction (c) showing atrioventricular discordance and ventriculoarterial discordance. Main pulmonary artery

narrowing (arrow) after pulmonary artery band placement is seen. LA morphologic left atrium (right-sided atrium), RA morphologic right atrium (left-sided atrium), LV morphologic left ventricle, RV morphologic right ventricle, AO aortic root, MPA main pulmonary artery

9  Atrioventricular Connections: Double-Inlet Ventricle, Atrioventricular Discordance, and Congenitally…

cardiac defects which generally are the cause of any clinically apparent signs and symptoms [12]. In rare patients, bradycardia may be the initial presenting symptom due to conduction system abnormality that prompts further evaluation including an electrocardiogram. Electrocardiogram shows Q waves in the right precordial leads and an absence of Q waves in the left-sided precordial leads. In patients with congenitally corrected transposition of great arteries, the great arteries do not normally cross and are parallel to one another with the aorta abnormally positioned anterior and superior and to the left of the pulmonary artery. Subcostal imaging often provides the best views to demonstrate that the posterior, inferior, and rightward pulmonary artery is associated with the morphologic left ventricle. Cardiac CT is crucial to evaluate associated cardiac lesions or after pulmonary artery band placement (Fig. 9.1).

Management Approach There are two surgical approaches: conventional repair and anatomic repair. The anatomic repair makes the morphologic left ventricle become the systemic ventricle and the morphologic right ventricle the pulmonary ventricle. There is limited data about optimal surgical approach in patients with congenitally corrected transposition. Hence, it is challenging to make surgical decision. It is very important to discuss with the family the potential benefits and complications of the proposed surgical procedures and the areas of uncertainty. The final decision is individualized based on our overall assessment of the patient’s potential for heart failure without anatomic correction versus the potential complications of the anatomic repair and the preference of the family. Complications related to anatomic repair (atrial and arterial switch) include arrhythmia, baffle obstruction, neo-aortic regurgitation, and left ventricular dysfunction. Anatomic repair is preferred in those patients with Ebstein-like malformation of the tricuspid valve, large ventricular septal defect, or obstruction to left ventricular outflow tract.

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Left ventricle can be trained to become systemic ventricle by placing pulmonary artery band (Fig.  9.1). This should be performed early in childhood. Altering the left and right ventricular pressure ratio may also reduce the right ventricular sphericity and improve the geometry of the right ventricle prior to anatomic correction [10]. Pulmonary artery band placement may stabilize systemic atrioventricular valve regurgitation and improves systemic ventricular function [10, 15, 16]. Typically, pulmonary artery band placement appears to be more successful in younger patients, and the younger the patient, the shorter the interval required for training [13, 15]. In most patients, the left ventricle is adequately trained for systemic circulation in 9–12 months. Pulmonary artery band placement can also be considered if there is associated large ventricular septal defect. In this setting, pulmonary artery band placement restricts pulmonary blood flow and promotes growth of the infant. Double-switch operation involves atrial and arterial switch components and is performed in patients without significant subpulmonary obstruction. Senning-Rastelli procedure is performed in patients with a large ventricular septal defect and left ventricular outflow tract obstruction. Double-switch operation consists of an atrial switch procedure that creates an intra-atrial baffle (Mustard or Senning procedure) and an arterial switch operation. The atrial switch operation can be modified to hemi-Mustard procedure with superior cavopulmonary anastomosis and baffling of inferior vena cava blood to pulmonary ventricle. This technique avoids superior vena cava baffle stenosis after atrial switch operation. The arterial switch operation involves transection of both great arteries, and then translocation of the vessels to the opposite root, similar to the arterial switch operation procedure performed for dextro-transposition of great arteries requiring coronary artery transfer. Cardiac CT plays a crucial role in the evaluation of the coronary artery anatomy. The Senning-Rastelli procedure involves intra-atrial baffle (Senning tunnel), and the ventricular septal defect is closed by a baffle so that the blood from the left ventricle is directed into

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the aorta, and a conduit is placed between the right ventricle and pulmonary artery (Rastelli procedure). The Rastelli procedure requires a sizable and appropriately located ventricular septal defect so that the baffle can be placed to redirect blood flow into the aorta. The right ventricular to pulmonary artery conduits may become stenotic, and cardiac CT is an important imaging modality to evaluate the conduit and coronary arteries.

V RA LA

Outcome Mortality rates following anatomic repair appear to be comparable or perhaps superior to those seen with conventional repair [16–19]. It is unclear whether survival differs among patients who undergo double-switch versus Senning-­ Rastelli procedure. Complications associated with anatomic correction in patients with congenitally corrected transposition of great arteries are primarily due to conduction abnormalities, left ventricular dysfunction, and neo-aortic valve regurgitation [20]. Surgical reintervention is common in patients who undergo either a double-switch operation or Senning-Rastelli procedure [14, 21–25].

Double-Inlet Ventricle Introduction Double-inlet ventricle is a form of single ventricle with both atrioventricular valves communicating with a common ventricle (Fig. 9.2). The common ventricle can have left ventricular morphology, right ventricular morphology, mixed morphology, or indeterminate morphology. Double-inlet left ventricle is the most common type of double-inlet ventricle. Double-inlet ventricle is mainly diagnosed by transthoracic echocardiography. Cardiac CT is extremely valuable for demonstration of extracardiac abnormalities of systemic and pulmonary venous connection and aortic arch and branch pulmonary artery abnormalities. Cardiac CT also helps in estab-

Fig. 9.2  An infant with double-inlet ventricle with both atrioventricular valves (arrows) communicating with common ventricle. RA right atrium, LA left atrium, V common ventricle

lishing cardiac segmental anatomy including visceroatrial situs, atrioventricular, and ventriculoarterial connection. Single-ventricle patients undergo palliative surgical procedures (Fig. 9.3).

Double-Inlet Left Ventricle Double-inlet left ventricle is the most common form of single ventricle. The great artery relationship is variable: normal relationship, right anterior aorta, left anterior aorta, or left posterior aorta. Subaortic obstruction usually occurs with ventricular-great artery discordance and is mainly at the ventricular septal defect level (bulboventricular foramen). Subpulmonary obstruction occurs with either concordant or discordant ventricular-­arterial connection. It is usually due to posterior deviation of conal septum.

Management Approach Pulmonary artery band placement is used for single-ventricle patients with no pulmonary stenosis (Fig.  9.4). CT scan is capable to provide anatomical and functional information useful for the surgical decision-making [26–32]. Different palliative procedures for single-ventricle patients are discussed under separate chapter in this book.

9  Atrioventricular Connections: Double-Inlet Ventricle, Atrioventricular Discordance, and Congenitally…

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b

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NAO NAO

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Fig. 9.3  An infant with double-inlet ventricle and subaortic stenosis who underwent Damus-Kaye-Stansel anastomosis (arrows). Coronal reconstructed image (a) and

AO RPA

LPA

Fig. 9.4  An infant with double-inlet ventricle with no pulmonary stenosis who underwent main pulmonary artery band placement (arrow) to restrict pulmonary blood flow. AO aortic root, LPA left pulmonary artery, RPA right pulmonary artery

References 1. Ferencz C, Rubin JD, McCarter RJ, et al. Congenital heart disease: prevalence at livebirth. The Baltimore-­ Washington Infant Study. Am J Epidemiol. 1985;121:31. 2. Report of the New England Regional Infant Cardiac Program. Pediatrics 1980; 65:375. 3. Samánek M, Vorísková M.  Congenital heart disease among 815,569 children born between 1980 and 1990 and their 15-year survival: a prospective Bohemia survival study. Pediatr Cardiol. 1999;20:411. 4. Dyck JD, Atallah JA.  Transposition of the great arteries. In: Allen HD, Shaddy RE, Driscoll DJ,

AO

three-dimensional volume rendered reconstruction (b). NAO neo-aortic root, AO native aortic root

Feltes TF, editors. Moss and Adams’ heart disease in infants, children, and adolescents: including the fetus and young adult. 7th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2008. p. 1087. 5. Warnes CA.  Transposition of the great arteries. Circulation. 2006;114:2699. 6. Hornung TS, Calder L. Congenitally corrected transposition of the great arteries. Heart. 2010;96:1154. 7. Kuehl KS, Loffredo CA.  Population-based study of l-transposition of the great arteries: possible associations with environmental factors. Birth Defects Res A Clin Mol Teratol. 2003;67:162. 8. Becker TA, Van Amber R, Moller JH, Pierpont ME. Occurrence of cardiac malformations in relatives of children with transposition of the great arteries. Am J Med Genet. 1996;66:28. 9. Hornung TS, Kilner PJ, Davlouros PA, et al. Excessive right ventricular hypertrophic response in adults with the mustard procedure for transposition of the great arteries. Am J Cardiol. 2002;90:800. 10. Kral Kollars CA, Gelehrter S, Bove EL, Ensing G.  Effects of morphologic left ventricular pressure on right ventricular geometry and tricuspid valve regurgitation in patients with congenitally corrected transposition of the great arteries. Am J Cardiol. 2010;105:735. 11. Hornung TS, Bernard EJ, Celermajer DS, et al. Right ventricular dysfunction in congenitally corrected transposition of the great arteries. Am J Cardiol. 1999;84:1116. 12. Wan AW, Jevremovic A, Selamet Tierney ES, et  al. Comparison of impact of prenatal versus postnatal diagnosis of congenitally corrected transposition of the great arteries. Am J Cardiol. 2009;104:1276. 13. Graham TP Jr, Bernard YD, Mellen BG, et al. Long-­ term outcome in congenitally corrected transposition

80 of the great arteries: a multi-institutional study. J Am Coll Cardiol. 2000;36:255. 14. Murtuza B, Barron DJ, Stumper O, et  al. Anatomic repair for congenitally corrected transposition of the great arteries: a single-institution 19-year experience. J Thorac Cardiovasc Surg. 2011;142:1348. 15. Myers PO, del Nido PJ, Geva T, et al. Impact of age and duration of banding on left ventricular preparation before anatomic repair for congenitally corrected transposition of the great arteries. Ann Thorac Surg. 2013;96:603. 16. Ma K, Gao H, Hua Z, et  al. Palliative pulmonary artery banding versus anatomic correction for congenitally corrected transposition of the great arteries with regressed morphologic left ventricle: long-term results from a single center. J Thorac Cardiovasc Surg. 2014;148:1566. 17. Devaney EJ, Charpie JR, Ohye RG, Bove EL. Combined arterial switch and Senning operation for congenitally corrected transposition of the great arteries: patient selection and intermediate results. J Thorac Cardiovasc Surg. 2003;125:500. 18. Bautista-Hernandez V, Marx GR, Gauvreau K, et al. Determinants of left ventricular dysfunction after anatomic repair of congenitally corrected transposition of the great arteries. Ann Thorac Surg. 2006;82:2059. 19. Lenoir M, Bouhout I, Gaudin R, et al. Outcomes of the anatomical repair in patients with congenitally corrected transposition of the great arteries: lessons learned in a high-volume centre. Eur J Cardiothorac Surg. 2018;54:532. 20. Mongeon FP, Connolly HM, Dearani JA, et  al. Congenitally corrected transposition of the great arteries ventricular function at the time of systemic atrioventricular valve replacement predicts long-term ventricular function. J Am Coll Cardiol. 2011;57:2008. 21. Hraska V, Vergnat M, Zartner P, et  al. Promising outcome of anatomic correction of corrected transposition of the great arteries. Ann Thorac Surg. 2017;104:650. 22. Hiramatsu T, Matsumura G, Konuma T, et al. Long-­ term prognosis of double-switch operation for congenitally corrected transposition of the great arteries. Eur J Cardiothorac Surg. 2012;42:1004.

R. Kharouf and D. A. Adebo 23. Malhotra SP, Reddy VM, Qiu M, et  al. The hemi-­ Mustard/bidirectional Glenn atrial switch procedure in the double-switch operation for congenitally corrected transposition of the great arteries: rationale and midterm results. J Thorac Cardiovasc Surg. 2011;141:162. 24. Spigel Z, Binsalamah ZM, Caldarone C. Congenitally corrected transposition of the great arteries: anatomic, physiologic repair, and palliation. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2019;22:32. 25. Brizard CP, Lee A, Zannino D, et  al. Long-term results of anatomic correction for congenitally corrected transposition of the great arteries: a 19-year experience. J Thorac Cardiovasc Surg. 2017;154:256. 26. Choi BW, Park YH, Lee JK, Kim DJ, Kim MJ, Choe KO. Patency of cavopulmonary connection studied by single phase electron beam computed tomography. Int J Cardiovasc Imaging. 2003;19:447–55. 27. Choi BW, Park YH, Choi JY, Choi BI, Kim MJ, Ryu SJ, Lee JK, Sul JH, Lee SK, Cho BK, Choe KO. Using electron beam CT to evaluate conotruncal anomalies in pediatric and adult patients. Am J Roentgenol. 2001;177:1045–9. 28. Goo HW, Park IS, Ko JK, Kim YH, Seo DM, Yun TJ, Park JJ, Yoon CH.  CT of congenital heart disease: normal anatomy and typical pathologic conditions. Radiographics. 2003;23:S147–65. 29. Goo HW.  Quantification of initial right ventricular dimensions by computed tomography in infants with congenital heart disease and a hypoplastic right ventricle. Korean J Radiol. 2020;21:203–9. 30. Gosnell J, Pietila T, Samuel BP, Kurup HK, Haw MP, Vettukattil JJ.  Integration of computed tomography and three-dimensional echocardiography for hybrid three-dimensional printing in congenital heart disease. J Digit Imaging. 2016;29:665–9. 31. Ito D, Shiraishi J, Noritake K, Kohno Y. Multidetector computer tomography demonstrates double-­ inlet, double-outlet right ventricle. Intern Med. 2011;50:2053–4. 32. Schneider K, Ghaleb S, Morales DLS, Tretter JT. Virtual dissection and endocast three-dimensional reconstructions: maximizing computed tomographic data for procedural planning of an obstructed pulmonary venous baffle. Cardiol Young. 2019;29:1104–6.

Right Ventricular Outflow Tract: Pulmonary Valve Stenosis

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Introduction

Embryology and Anatomy

Pulmonary valve stenosis is a common congenital heart defect that accounts for approximately 8–10% of cardiac birth defects [1–3]. Severe pulmonary valve stenosis is associated with right ventricular hypertrophy and infundibular muscle hypertrophy, which can cause further dynamic obstruction below the pulmonary valve during right ventricular contraction. Critical pulmonary valve stenosis is the most severe form of pulmonary stenosis, resulting in an inadequate antegrade pulmonary blood flow. As a result, survival for such patients is dependent upon maintaining a patent ductus arteriosus for pulmonary blood flow. Pulmonary stenosis can be associated with different syndromes such as Noonan syndrome, Alagille syndrome, Williams syndrome, or congenital rubella syndrome.

Pulmonary valve stenosis is typically characterized by fused or absent commissures with thickened leaflets of the pulmonary valve. In most patients, the valve is a dome-shaped structure with a small orifice [4]. At the end of the 5th week of gestation, the pulmonary valve develops from a section of the conotruncus and begins moving from a position that is posterior of the aortic valve to one that is anterior and leftward of the aortic valve. It has been postulated that valvular pulmonary stenosis is due to a maldevelopment of the distal portion of the conotruncus, but there are no data to support this theory.

D. A. Adebo (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

Diagnosis Transthoracic echocardiography is the first-line imaging modality for the diagnosis of valvular pulmonary stenosis. Echocardiography provides excellent visualization of the anatomy of the pulmonary valve annulus, easy localization of the stenosis, and evaluation of right ventricular size and function. Continuous-wave Doppler echocardiography can assess the severity of stenosis by estimation of the pressure gradient across the pulmonary valve. Other imaging modalities are usually not necessary for diagnosis of pulmonary valve stenosis. However, in some cases in which there is associated branch pulmonary artery

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_10

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a

b AO

LPA AO

MPA LPA

Fig. 10.1  An infant with pulmonary stenosis. Cardiac CT with axial reconstructed image (a) and three-dimensional volume rendered reconstruction from posterior aspect (b)

showing hypoplastic pulmonary valve annulus and right pulmonary artery (arrows). AO aortic root, LPA left pulmonary artery, MPA main pulmonary artery

s­tenosis, cardiac CT is a useful non-invasive imaging modality that provides excellent visualization of branch pulmonary arteries (Fig. 10.1).

Outcome

Management Approach Critical pulmonary stenosis is a life-threatening condition in the neonate because of inadequate antegrade pulmonary blood flow. Survival is dependent on maintaining patency of the ductus arteriosus by the administration of prostaglandin infusion to provide adequate pulmonary blood flow [5–7]. Percutaneous balloon pulmonary valvuloplasty was first described by Kan et  al. in 1982. Since then, it has been improved to the point that it is now established as the preferred therapy for valvular pulmonary stenosis because of its safety and effectiveness [6–11]. Cardiac catheterization has become primarily a therapeutic intervention rather than a diagnostic procedure in children with pulmonary stenosis [12–21]. When intervention is indicated, balloon pulmonary valvuloplasty is generally the procedure of choice. However, surgical correction may be required in some patients with associated supravalvular and subvalvular pulmonary stenosis or with dysplastic pulmonary valves and a hypoplastic pulmonary valve annulus or hypoplastic pulmonary artery.

The long-term outcome for children with pulmonary stenosis who undergo catheter-based or surgical intervention is excellent [22–29].

References 1. Cuypers JA, Witsenburg M, van der Linde D, Roos-­ Hesselink JW. Pulmonary stenosis: update on diagnosis and therapeutic options. Heart. 2013;99:339–47. https://doi.org/10.1136/heartjnl-­2012-­301964. 2. Rao PS.  Percutaneous balloon pulmonary valvuloplasty: State of the art. Catheter Cardiovasc Interv. 2007;69:747–63. https://doi.org/10.1002/ccd.20982. 3. Rao PS.  Further observations on the effect of balloon size on the short term and intermediate term results of balloon dilatation of the pulmonary valve. Br Heart J. 1988;60:507–11. https://doi.org/10.1136/ hrt.60.6.507. 4. Edwards JE.  Congenital malformations of the heart and great vessels. In: Gould SE, editor. Pathology of the heart. Springfield: Charles C. Thomas Publisher; 1953. 5. Feltes TF, Bacha E, Beekman RH 3rd, et  al. Indications for cardiac catheterization and intervention in pediatric cardiac disease: a scientific statement from the American Heart Association. Circulation. 2011;123:2607. 6. Freed MD, Rosenthal A, Bernhard WF, et al. Critical pulmonary stenosis with a diminutive right ventricle in neonates. Circulation. 1973;48:875. 7. Liu TL, Gao WButera G.  Pulmonary valve stenosis Cardiac Catheterization for Congenital Heart Disease.

10  Right Ventricular Outflow Tract: Pulmonary Valve Stenosis 1st ed. New York/Dordrecht/London: Springer, Milan Heidelberg; 2015. p. 261–77. 8. Echigo S. Balloon valvuloplasty for congenital heart disease: Immediate and long-term results of multi-­ institutional study. Pediatr Int. 2001;43:542–7. https:// doi.org/10.1046/j.1442-­200X.2001.01461. 9. Silvilairat S, Pongprot Y, Sittiwangkul R, Phornphutkul C. Factors determining immediate and medium-term results after pulmonary balloon valvuloplasty. J Med Assoc Thail. 2006;89:1404–11. 10. Ghaffari S, Ghaffari MR, Ghaffari AR, Sagafy S.  Pulmonary valve balloon valvuloplasty compared across three age groups of children. Int J Gen Med. 2012;5:479–82. https://doi.org/10.2147/IJGM. S27203. 11. Behjati-Ardakani M, Forouzannia SK, Abdollahi MH, Sarebanhassanabadi M. Immediate, short, intermediate and long-term results of balloon valvuloplasty in congenital pulmonary valve stenosis. Acta Med Iran. 2013;51:324–8. 12. Chen CR, Cheng TO, Huang T, Zhou YL, Chen JY, Huang YG, et al. Percutaneous balloon valvuloplasty for pulmonic stenosis in adolescents and adults. N Engl J Med. 1996;335:21–5. https://doi.org/10.1056/ NEJM199607043350104. 13. Gournay V, Piechaud JF, Delogu A, Sidi D, Kachaner J.  Balloon valvotomy for critical stenosis or atresia of pulmonary valve in newborns. J Am Coll Cardiol. 1995;26:1725–31. https://doi. org/10.1016/0735-­1097(95)00369-­X14. 14. Holzer RJ, Gauvreau K, Kreutzer J, Trucco SM, Torres A, Shahanavaz S, et al. Safety and efficacy of balloon pulmonary valvuloplasty: a multicenter experience. Catheter Cardiovasc Interv. 2012;80:663–72. https://doi.org/10.1002/ccd.23473. 15. Lee ML, Peng JW, Tu GJ, Chen SY, Lee JY, Chang SL, et  al. Major determinants and long-term outcomes of successful balloon dilatation for the pediatric patients with isolated native valvular pulmonary stenosis: a 10-year institutional experience. Yonsei Med J. 2008;49:416–21. https://doi.org/10.3349/ ymj.2008.49.3.416. 16. Maostafa BA, Seyed-Hossien M, Shahrokh R. Long-­ term results of balloon pulmonary valvuloplasty in children with congenital pulmonary valve stenosis. Iran J Pediatr. 2013;23:32–6. 17. Merino-Ingelmo R, Santos-de Soto J, Coserria-­ Sanchez F, Descalzo-Senoran A, Valverde-Perez I.  Long-term results of percutaneous balloon valvuloplasty in pulmonary valve stenosis in the pediatric population. Rev Esp Cardiol (Engl Ed). 2014;67:374– 9. https://doi.org/10.1016/j.rec.2013.08.020. 18. Tabatabaei H, Boutin C, Nykanen DG, Freedom RM, Benson LN.  Morphologic and hemodynamic consequences after percutaneous balloon valvotomy for neonatal pulmonary stenosis: medium-term follow-

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u­ p. J Am Coll Cardiol. 1996;27:473–8. https://doi. org/10.1016/0735-­1097(95)00477-­7. 19. Santoro G, Formigari R, Di Carlo D, Pasquini L, Ballerini L.  Midterm outcome after pulmonary balloon valvuloplasty in patients younger than one year of age. Am J Cardiol. 1995;75:637–9. https://doi. org/10.1016/s0002-­9149(99)80638-­9. 20. Fedderly RT, Lloyd TR, Mendelsohn AM, Beekman RH.  Determinants of successful balloon valvotomy in infants with critical pulmonary stenosis or membranous pulmonary atresia with intact ventricular septum. J Am Coll Cardiol. 1995;25:460–5. https://doi. org/10.1016/0735-­1097(94)00405-­f. 21. Stamm C, Anderson RH, Ho SY.  Clinical anatomy of the normal pulmonary root compared with that in isolated pulmonary valvular stenosis. J Am Coll Cardiol. 1998;31:1420–5. https://doi.org/10.1016/ S0735-­1097(98)00089-­8. 22. McCrindle BW.  Independent predictors of long-­ term results after balloon pulmonary valvuloplasty. Valvuloplasty and angioplasty of congenital anomalies (VACA) registry investigators. Circulation. 1994;89:1751–9. https://doi.org/10.1161/01. CIR.89.4.1751. 23. Peterson C, Schilthuis JJ, Dodge-Khatami A, Hitchcock JF, Meijboom EJ, Bennink GB, et  al. Comparative long-term results of surgery versus balloon valvuloplasty for pulmonary valve stenosis in infants and children. Ann Thorac Surg. 2003;76:1078– 82. https://doi.org/10.1016/s0003-­4975(03)00678-­7. 24. Roos-Hesselink JW, Meijboom FJ, Spitaels SE, van Domburg RT, van Rijen EH, Utens EM, et al. Long-­ term outcome after surgery for pulmonary stenosis (a longitudinal study of 22–33 years). Eur Heart J. 2006;27:482–8. https://doi.org/10.1093/eurheartj/ ehi685. 25. Sehar T, Qureshi AU, Kazmi U, Mehmood A, Hyder SN, Sadiq M, et  al. Balloon valvuloplasty in dysplastic pulmonary valve stenosis: immediate and intermediate outcomes. J Coll Physicians Surg Pak. 2015;25:16–21. https://doi.org/10.2015/JCPSP.1621. 26. Garty Y, Veldtman G, Lee K, Benson L.  Late outcomes after pulmonary valve balloon dilatation in neonates, infants and children. J Invasive Cardiol. 2005;17:318. 27. Rao PS, Galal O, Patnana M, et al. Results of three to 10 year follow up of balloon dilatation of the pulmonary valve. Heart. 1998;80:591. 28. Roos-Hesselink JW, Meijboom FJ, Spitaels SE, et al. Long-term outcome after surgery for pulmonary stenosis (a longitudinal study of 22-33 years). Eur Heart J. 2006;27:482. 29. Earing MG, Connolly HM, Dearani JA, et al. Long-­ term follow-up of patients after surgical treatment for isolated pulmonary valve stenosis. Mayo Clin Proc. 2005;80:871.

Right Ventricular Outflow Tract: Pulmonary Atresia with Intact Ventricular Septum

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Introduction Pulmonary atresia with intact ventricular septum is a rare congenital heart defect which includes pulmonary atresia with no antegrade blood flow from the right ventricle to pulmonary artery and intact ventricular septum. The pulmonary atresia can be valvar (membranous) or muscular [1–4]. Pulmonary atresia with intact ventricular septum accounts for about 2% of all congenital cardiac defects in children. There is no difference in the incidence based on gender. There is a varying degree of hypoplasia of the right ventricle and tricuspid valve annulus. The mortality is 100% if not treated.

Techniques of Cardiac CT The exact mechanism of pathogenesis of pulmonary atresia with intact ventricular septum is unknown. It is thought that pulmonary atresia with intact ventricular septum is due to abnormal fetal blood flow. Pulmonary atresia with intact ventricular septum is a duct-dependent congeniD. A. Adebo (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

tal heart disease with a spectrum of lesions, which include pulmonary atresia, variable degrees of hypoplasia of the right ventricle and tricuspid valve, and anomalies of the coronary circulation [5]. The abnormal coronary artery system includes persistent fetal sinusoids, coronary fistula to the right ventricle, atresia of aortocoronary connection, stenosis of the normally branching coronary arteries, or abnormal connection between the right and left coronary system [6–9]. In 25% of the cases, there is a right ventricle-­ dependent coronary circulation. Recognition of this clinical scenario is important, because right ventricular decompression may lead to coronary ischemia and sudden cardiac death when the right ventricular outflow tract obstruction is relieved [10]. The pulmonary blood flow is usually supplied by patent ductus arteriosus connecting to confluent pulmonary arteries (Fig.  11.1). Rarely, patients with pulmonary atresia and intact ventricular septum have abnormal development of the pulmonary arteries and connections from the aorta to the pulmonary arteries via major aortopulmonary collateral arteries [11]. Other less common anatomic defects may include aortic valve stenosis, left ventricular outflow tract obstruction, and left ventricular dysfunction due to coronary insufficiency.

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a

b AAR PDA LPA

RV RPA

LV

RA LA

c

AO

RPA

LPA

Fig. 11.1  A neonate with pulmonary atresia and intact ventricular septum. Cardiac CT volume rendered reconstruction in posterior view (a) showing large patent ductus arteriosus arising from underside of the aortic arch supplying branch pulmonary arteries and four-chamber view multiplanar reconstructed image (b) showing severely

hypoplastic right ventricle. Coronary arteries are seen on axial reconstructed image (arrows) (c). PDA patent ductus arteriosus, AAR aortic arch, Ao aortic root, RAP right pulmonary artery, LPA left pulmonary artery, LA left atrium, RA right atrium, RV right ventricle, LV left ventricle

Diagnosis

Management Approach

Diagnosis of pulmonary atresia with intact ventricular septum is generally made by echocardiography. However, cardiac CT may be needed to better delineate branch pulmonary arteries and coronary artery abnormality (Figs. 11.2 and 11.3). Cardiac catheterization is essential to identify right ventricle-dependent coronary artery system.

The management of pulmonary atresia with intact ventricular septum includes initial stabilization with prostaglandin E1 infusion to maintain patency of the ductus arteriosus, which typically provides the sole source of pulmonary blood flow, followed by corrective repair or palliation. These patients may undergo biventricular repair, 1.5 ventricle repair, univentricular

11  Right Ventricular Outflow Tract: Pulmonary Atresia with Intact Ventricular Septum

a

87

b IA

IA Ao mBT

AO

RPA

mBT RPA

Fig. 11.2  An infant with pulmonary atresia and intact ventricular septum after modified Blalock-Taussig shunt (mBT) placement. Cardiac CT multiplanar reconstruction in coronal view (a) and volume rendered reconstruction in

SVC

LPA

RPA

posterior view (b) showing patent mBT shunt and hypoplastic branch pulmonary arteries. mBT modified BT shunt, RPA right pulmonary artery, Ao aorta, IA innominate artery

of coronary arteries usually undergo successful biventricular repair. Univentricular palliation is considered when tricuspid valve Z-score  40 mmHg with symptoms are candidates for balloon valvuloplasty.

Outcomes Critical aortic stenosis is a lethal disease. Early mortality for critical AS after balloon

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v­ alvuloplasty is reported to be between 9% and 14%. In neonates, incidence of moderate or severe aortic regurgitation shortly after balloon valvuloplasty is reported to be between 7% and 33% [22, 26]. There is about 27% freedom from re-intervention after balloon valvuloplasty versus 65% after surgical valvuloplasty at 5  years of follow-up [20]. Balloon valvuloplasty is safe and effective in relieving congenital aortic stenosis in the current era but is associated with long-term risks of valve dysfunction and need for re-­ intervention, including aortic valve replacement. Aortic regurgitation is more strongly associated with neonatal intervention [27]. Balloon and surgical valvuloplasty for non-critical aortic stenosis in a single-center study showed comparable early and late follow-­up results [28]. Ross procedure has been shown to have excellent outcomes with no mortality and a low incidence of aortic insufficiency when performed in children older than 1 year of age. Ross procedure in children younger than 1 year of age is associated with higher operative mortality and a higher incidence of aortic insufficiency [29].

Subvalvar Aortic Stenosis Anomalies of left ventricular outflow tract resulting in LV flow obstruction are grouped under this diagnosis. Membranous subaortic stenosis is the most common form with a thin circumferential diaphragm-like membrane seen below the aortic valve. Fibromuscular subaortic membrane is the second most common variety accounting for about 20% [1]. Subvalvar aortic stenosis is associated with other congenital heart defects such as ventricular septal defect when there is malaligned conal septum and might contribute to hypoplastic downstream structures resulting in coarctation or aortic interruption [8]. Hypertrophic cardiomyopathy may also result in some degree of subvalvar stenosis. Neonatal presentation with significant obstruction is rare, and it is often considered as an acquired lesion. Abnormal shear stress due to small aorto-septal angle is thought to result in exaggerated fibrous tissue growth and a good likelihood of recurrence following inter-

S. C. Uppu

vention [1, 13]. This can occur as part of Shone’s complex [30].

Diagnosis Echocardiography is imaging modality of choice; it provides anatomic and functional details including the mechanism of the subvalvar stenosis, severity, and presence of associated findings. There is no need for routine cardiac MRI or cardiac CT for this anomaly. Management Surgical intervention is the treatment of choice in symptomatic patients or with LV systolic dysfunction. Surgery is considered in asymptomatic patients where there is progressive aortic regurgitation or peak gradients greater than 50  mmHg [31]. Surgical procedure depends on the nature of the subaortic obstruction, size of the aortic valve, and need for aortic valve repair; interventions range from resection of subaortic membrane to myectomy, modified Konno, and Ross-Konno procedures. Detailed description into the decision-­ making and surgical explanation is beyond the scope of this chapter [13, 32–34]. Outcomes Surgical outcomes for subaortic stenosis repair are excellent with survival at 10 and 20 years of 98.6% and 86.3%, respectively. About 20% patients are at risk for recurrence of subaortic stenosis and aortic regurgitation, especially in those patients who were operated at younger age, distance of the membrane less than 7 mm from aortic valve, severe preoperative aortic stenosis (peak gradient >60 mmHg), and residual postoperative stenosis, and those requiring peeling of the membrane from the aortic and mitral valves are at higher risk [35, 36]. In comparison, progression of subaortic membrane in adults is slower [37]. Recurrence has been shown to be minimal when extensive septal myectomy was performed at the initial surgery [38]. It has been suggested that children at risk for recurrence may have an underlying genetic disease [39]. Postoperative complete heart block is a potential complication in about 18% requiring extensive myectomy [40]. Aortic regurgitation might

15  Left Ventricular Outflow Tract: Congenital Aortic Valve and Left Ventricular Outflow Anomalies

c­ ontinue to progress even after successful surgical relief of subaortic obstruction [38].

Supravalvar Aortic Stenosis Supravalvar aortic stenosis is less common compared to other forms of left ventricular outflow tract obstruction. The typical supravalvar aortic stenosis is described as an hourglass narrowing at the level of sinotubular junction but can extend into the ascending aorta [13]. It is considered as a form of aortopathy with mutations involving the elastin gene (Williams syndrome); manifestations include variable range of aortic obstruction extending to thoracic and abdominal aorta, pulmonary artery stenosis, and diffuse arteriopathy in extreme cases involving any systemic artery [41]. Aortic valve tethering to the narrowed portion with limited excursion as well as coronary ostial stenosis has been described with this diagnosis [1]. Significant afterload on the LV results in compensatory hypertrophy, due to the location of the supravalvar stenosis; coronary arteries are also exposed to higher pressure resulting in coronary ostial thickening and increased risk for premature atherosclerosis [42]. Cardiovascular abnormalities are considered as the leading cause of morbidity and mortality in these patients. Fetal diagnosis is rare, and supravalvar aortic stenosis is a progressive disease, whereas the associated pulmonary stenosis improves with age [8].

Diagnosis Echocardiography is the primary imaging modality, and it provides anatomic and functional details including the mechanism of the supravalvular stenosis, severity, and presence of associated findings. There is a role for cardiac MRI or cardiac CT to better understand the associated arteriopathy by imaging the entire aorta and accurately identifying the location and extent of stenosis. Coronary artery imaging is also better with cardiac CT imaging; some centers recommend routine CT screening prior to surgical intervention [43]. Diagnostic cardiac catheterization might be necessary to accurately understand

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the hemodynamic burden and for coronary evaluation.

Management Patients with supravalvar aortic stenosis have secondary hypertension and might benefit from medical treatment. Transcatheter interventions with balloon angioplasty and stent placements are likely not beneficial in these patients due to the higher risk of underlying vessel and valve injury. Surgical intervention is recommended with moderate-severe stenosis and associated symptoms. Various surgical techniques have been described to relieve the obstruction [42, 44]. The surgical plan has to be tailored for the patient based on the location of the obstruction and need for additional interventions. Outcomes Sudden death is 25–100 times higher in Williams syndrome patients than the general population and is thought to be due to acute coronary insufficiency and likely QTc abnormalities. Periprocedural risk stratification for patients requiring anesthesia has been proposed to improve their outcomes [41]. Higher mortality and reoperation rates of about 16% were reported for patients undergoing surgical management years later. Most causes of mortality were attributed to coronary issues [45, 46]. Close follow-up of these patients including coronary imaging is routinely recommended.

References 1. Simpson JM, Miller OI. Anomalies of the left ventricular outflow tract and aortic valve. In: Lai WW, Mertens LL, Cohen MS, Geva T, editors. Echocardiography in pediatric and congenital heart disease: from fetus to adult. Oxford: Wiley; 2016. p. 336–56. 2. Hancock EW.  Differentiation of valvar, subvalvar and supravalvar aortic stenosis. Guys Hosp Rep. 1961;110:1–30. 3. Goldberg DJ, Thacker D.  Aortic stenosis. Fetal cardiovascular imaging a disease-based approach. Philadelphia: Elsevier/Saunders; 2012. p. 206–16. 4. Liu Y, Chen S, Zühlke L, Black GC, Choy M-K, Li N, et  al. Global birth prevalence of congenital heart defects 1970-2017: updated systematic review

112 and meta-analysis of 260 studies. Int J Epidemiol. 2019;48:455–63. https://doi.org/10.1093/ije/dyz009. 5. Siu SC, Silversides CK. Bicuspid aortic valve disease. J Am Coll Cardiol. 2010;55:2789–800. https://doi. org/10.1016/j.jacc.2009.12.068. 6. Martin PS, Kloesel B, Norris RA, Lindsay M, Milan D, Body SC. Embryonic development of the bicuspid aortic valve. J Cardiovasc Dev Dis. 2015;2:248–72. https://doi.org/10.3390/jcdd2040248. 7. Sadler TW.  Langman’s medical embryology, 14e. 2019; 8. Friedland-Little JM, Zampi JD, Gajarski RJ.  Aortic stenosis. In: Allen HD, Shaddy RE, Penny DJ, Feltes TF, Cetta F, editors. Moss and Adams’ heart disease in infants, children, and adolescents: including the fetus and young adult. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2016. p. 1085–106. 9. Friedman KG, Sleeper LA, Freud LR, Marshall AC, Godfrey ME, Drogosz M, et  al. Improved technical success, postnatal outcome and refined predictors of outcome for fetal aortic valvuloplasty. Ultrasound Obstet Gynecol. 2018;52:212–20. https://doi. org/10.1002/uog.17530. 10. Pickard SS, Wong JB, Bucholz EM, Newburger JW, Tworetzky W, Lafranchi T, et  al. Fetal aortic valvuloplasty for evolving hypoplastic left heart syndrome: a decision analysis. Circ Cardiovasc Qual Outcomes. 2020;13:e006127. https://doi.org/10.1161/ CIRCOUTCOMES.119.006127. 11. Keane JF, Fyler DC. Aortic outflow abnormalities. In: Keane JF, Lock JE, Fyler DC, editors. Nadas’ pediatric cardiology. 2nd ed. Philadelphia: Saunders; 2006. p. 581–601. 12. Singh GK, Mowers KL, Marino C, Balzer D, Rao PS.  Effect of pressure recovery on pressure gradients in congenital stenotic outflow lesions in pediatric patients-clinical implications of lesion severity and geometry: a simultaneous Doppler echocardiography and cardiac catheter correlative study. J Am Soc Echocardiogr. 2020;33:207–17. https://doi. org/10.1016/j.echo.2019.09.001. 13. Spicer DE, Hraska V, Anderson RH, Ginde S, Block JR. Congenital anomalies of the aortic valve and left ventricular outflow tract. In: Gi W, editor. Anderson’s pediatric cardiology. 4th ed. Philadelphia: Elsevier; 2020. p. 819–42. 14. Rhodes LA, Colan SD, Perry SB, Jonas RA, Sanders SP.  Predictors of survival in neonates with critical aortic stenosis. Circulation. 1991;84:2325–35. https:// doi.org/10.1161/01.cir.84.6.2325. 15. Corno AF.  Borderline left ventricle. Eur J Cardiothorac Surg. 2005;27:67–73. https://doi. org/10.1016/j.ejcts.2004.10.034. 16. Colan SD, McElhinney DB, Crawford EC, Keane JF, Lock JE.  Validation and re-evaluation of a discriminant model predicting anatomic suitability for biventricular repair in neonates with aortic stenosis. J Am Coll Cardiol. 2006;47:1858–65. https://doi. org/10.1016/j.jacc.2006.02.020.

S. C. Uppu 17. Hickey EJ, Caldarone CA, Blackstone EH, Lofland GK, Yeh T, Pizarro C, et  al. Critical left ventricular outflow tract obstruction: the disproportionate impact of biventricular repair in borderline cases. J Thorac Cardiovasc Surg. 2007;134:1429–36; discussion 1436. https://doi.org/10.1016/j.jtcvs.2007.07.052. 18. Hraška V.  Neonatal aortic stenosis is a surgical disease. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2016;19:2–5. https://doi.org/10.1053/j. pcsu.2015.11.002. 19. Benson L. Neonatal aortic stenosis is a surgical disease: an interventional cardiologist view. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2016;19:6–9. https://doi.org/10.1053/j.pcsu.2015.11.008. 20. Siddiqui J, Brizard CP, Galati JC, Iyengar AJ, Hutchinson D, Konstantinov IE, et al. Surgical valvotomy and repair for neonatal and infant congenital aortic stenosis achieves better results than interventional catheterization. J Am Coll Cardiol. 2013;62:2134–40. https://doi.org/10.1016/j.jacc.2013.07.052. 21. Backer CL. Infant congenital aortic valve stenosis: the pendulum swings. J Am Coll Cardiol. 2013;62:2141– 3. https://doi.org/10.1016/j.jacc.2013.07.053. 22. Torres A, Vincent JA, Everett A, Lim S, Foerster SR, Marshall AC, et al. Balloon valvuloplasty for congenital aortic stenosis: multi-center safety and efficacy outcome assessment. Catheter Cardiovasc Interv. 2015;86:808–20. https://doi.org/10.1002/ccd.25969. 23. McElhinney DB, Lock JE, Keane JF, Moran AM, Colan SD.  Left heart growth, function, and reintervention after balloon aortic valvuloplasty for neonatal aortic stenosis. Circulation. 2005;111:451–8. https:// doi.org/10.1161/01.CIR.0000153809.88286.2E. 24. Woods RK, Pasquali SK, Jacobs ML, Austin EH, Jacobs JP, Krolikowski M, et al. Aortic valve replacement in neonates and infants: an analysis of the Society of Thoracic Surgeons Congenital Heart Surgery Database. J Thorac Cardiovasc Surg. 2012;144:1084– 9. https://doi.org/10.1016/j.jtcvs.2012.07.060. 25. Ross DN.  Replacement of aortic and mitral valves with a pulmonary autograft. Lancet. 1967;2:956–8. https://doi.org/10.1016/s0140-­6736(67)90794-­5. 26. Brown DW, Dipilato AE, Chong EC, Lock JE, McElhinney DB.  Aortic valve reinterventions after balloon aortic valvuloplasty for congenital aortic stenosis intermediate and late follow-up. J Am Coll Cardiol. 2010;56:1740–9. https://doi.org/10.1016/j. jacc.2010.06.040. 27. Sullivan PM, Rubio AE, Johnston TA, Jones TK. Long-term outcomes and re-interventions following balloon aortic valvuloplasty in pediatric patients with congenital aortic stenosis: a single-center study. Catheter Cardiovasc Interv. 2017;89:288–96. https:// doi.org/10.1002/ccd.26722. 28. Prijic SM, Vukomanovic VA, Stajevic MS, Bjelakovic BB, Zdravkovic MD, Sehic IN, et  al. Balloon dilation and surgical valvotomy comparison in non-­ critical congenital aortic valve stenosis. Pediatr Cardiol. 2015;36:616–24. https://doi.org/10.1007/ s00246-­014-­1056-­6.

15  Left Ventricular Outflow Tract: Congenital Aortic Valve and Left Ventricular Outflow Anomalies 29. Donald JS, Wallace FRO, Naimo PS, Fricke TA, Brink J, Brizard CP, et  al. Ross operation in children: 23-year experience from a single institution. Ann Thorac Surg. 2020;109:1251–9. https://doi. org/10.1016/j.athoracsur.2019.10.070. 30. Shone JD, Sellers RD, Anderson RC, Adams P, Lillehei CW, Edwards JE.  The developmental complex of “parachute mitral valve,” supravalvular ring of left atrium, subaortic stenosis, and coarctation of aorta. Am J Cardiol. 1963;11:714–25. https://doi. org/10.1016/0002-­9149(63)90098-­5. 31. Gersony WM.  Natural history of discrete subvalvar aortic stenosis: management implications. J Am Coll Cardiol. 2001;38:843–5. https://doi.org/10.1016/ s0735-­1097(01)01454-­1. 32. Mavroudis C, Mavroudis CD, Jacobs JP.  The Ross, Konno, and Ross-Konno operations for congenital left ventricular outflow tract abnormalities. Cardiol Young. 2014;24:1121–33. https://doi.org/10.1017/ S1047951114002042. 33. Mavroudis C, Backer CL.  Technical tips for three congenital heart operations: modified Ross-Konno procedure, optimal ventricular septal defect exposure by tricuspid valve incision, coronary unroofing and endarterectomy for anomalous aortic origin of the coronary artery. Oper Tech Thorac Cardiovasc Surg. 2010;15:18–40. https://doi.org/10.1053/j. optechstcvs.2009.06.008. 34. Hraska V, Photiadis J, Arenz C.  Surgery for subvalvar aortic stenosis  – resection of discrete subvalvar aortic membrane. Multimed Man Cardiothorac Surg. 2007;2007:mmcts.2006.002303. https://doi. org/10.1510/mmcts.2006.002303. 35. Pickard SS, Geva A, Gauvreau K, del Nido PJ, Geva T.  Long-term outcomes and risk factors for aortic regurgitation after discrete subvalvular aortic stenosis resection in children. Heart. 2015;101:1547–53. https://doi.org/10.1136/heartjnl-­2015-­307460. 36. Dodge-Khatami A, Schmid M, Rousson V, Fasnacht M, Doell C, Bauersfeld U, et al. Risk factors for reoperation after relief of congenital subaortic stenosis. Eur J Cardiothorac Surg. 2008;33:885–9. https://doi. org/10.1016/j.ejcts.2008.01.049. 37. van der Linde D, Takkenberg JJM, Rizopoulos D, Heuvelman HJ, Budts W, van Dijk APJ, et al. Natural

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history of discrete subaortic stenosisin adults: a multicentre study. Eur Heart J. 2013;34:1548–56. https:// doi.org/10.1093/eurheartj/ehs421. 38. Binsalamah ZM, Spigel ZA, Zhu H, Kim MB, Chacon-Portillo MA, Adachi I, et  al. Reoperation after isolated subaortic membrane resection. Cardiol Young. 2019;29:1391–6. https://doi.org/10.1017/ S1047951119002336. 39. Mukadam S, Gordon BM, Olson JT, Newcombe JB, Hasaniya NW, Razzouk AJ, et al. Subaortic stenosis resection in children: emphasis on recurrence and the fate of the aortic valve. World J Pediatr Congenit Heart Surg. 2018;9:522–8. https://doi. org/10.1177/2150135118776931. 40. Jou CJ, Etheridge SP, Minich LL, Saarel EV, Lambert LM, Kouretas PC, et al. Long-term outcome and risk of heart block after surgical treatment of subaortic stenosis. World J Pediatr Congenit Heart Surg. 2010;1:15– 9. https://doi.org/10.1177/2150135109359530. 41. Collins RT.  Cardiovascular disease in Williams syndrome. Curr Opin Pediatr. 2018;30:609–15. https:// doi.org/10.1097/MOP.0000000000000664. 42. Stamm C, Friehs I, Ho SY, Moran AM, Jonas RA, del Nido PJ. Congenital supravalvar aortic stenosis: a simple lesion? Eur J Cardiothorac Surg. 2001;19:195– 202. https://doi.org/10.1016/s1010-­7940(00)00647-­3. 43. Mongé MC, Eltayeb OM, Costello JM, Johnson JT, Popescu AR, Rigsby CK, et  al. Brom aortoplasty for supravalvular aortic stenosis. World J Pediatr Congenit Heart Surg. 2018;9:139–46. https://doi. org/10.1177/2150135118754520. 44. Deo SV, Burkhart HM, Dearani JA, Schaff HV.  Supravalvar aortic stenosis: current surgical approaches and outcomes. Expert Rev Cardiovasc Ther. 2013;11:879–90. https://doi.org/10.1586/14779 072.2013.811967. 45. Roemers R, Kluin J, de Heer F, Arrigoni S, Bökenkamp R, van Melle J, et al. Surgical correction of supravalvar aortic stenosis: 52 years’ experience. World J Pediatr Congenit Heart Surg. 2018;9:131–8. https://doi.org/10.1177/2150135117745004. 46. d’Udekem Y.  Pitfalls of supra-aortic valve stenosis repair: let us intensify their follow-up screening! World J Pediatr Congenit Heart Surg. 2018;9:147–9. https://doi.org/10.1177/2150135118761030.

Left Ventricular Outflow Tract: Hypoplastic Left Heart Syndrome

16

Santosh C. Uppu and Mehul D. Patel

Introduction Hypoplastic left heart syndrome (HLHS) includes a variable combination of mitral and aortic stenosis or atresia along with the underdeveloped left ventricle and aorta ultimately resulting in a small left ventricle (LV) that is incapable of maintaining systemic circulation [1–3]. The international working group for mapping and coding of nomenclatures for pediatric and congenital heart disease, the nomenclature working group, has discussed the HLHS at length, but the intact ventricular septum was still not part of their HLHS definition; they described it as “a spectrum of cardiac malformations with normally aligned great arteries without a common atrioventricular junction, characterized by underdevelopment of the left heart with significant hypoplasia of the left ventricle including atresia, stenosis, or hypoplasia of the aortic or mitral valve, or both valves, and hypoplasia of the ascending aorta and aortic arch” [4, 5]. Lev made earlier descriptions of this anomaly, but it was Noonan and Nadas who first used the term hypoplastic left heart syndrome [6,

S. C. Uppu (*) · M. D. Patel Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]; [email protected]

7]. A recent systematic review has reported the prevalence of hypoplastic left heart syndrome as 1.78 per 1000 live births accounting for 2.5% of all congenital heart defects [8]. Anomalies with normal-sized left ventricle as a result of ventricular septal defect and double-outlet right ventricle but with aortic or mitral valve stenosis or atresia that are defined as part of hypoplastic left heart complex will not be discussed in this chapter. Untreated HLHS is fatal with 100% neonatal mortality. Multistage surgical repair with the ultimate goal to achieve single-ventricle physiology has changed the outlook of HLHS, with most individuals surviving to the third decade [9]. Single-ventricle physiology has its own set of challenges due to elevated systemic venous pressure and lack of subpulmonary ventricle, but knowledge of this unique physiology is necessary for appropriate management and to address potential complications in this population [10]. Other interventions include heart transplantation and biventricular repair in a carefully selected population where the mitral and aortic valves can potentially be repaired along with a non-­ prohibitive left ventricle.

Embryology and Anatomy Similar to other congenital heart defects of the left heart (such as aortic stenosis or coarctation of the aorta), HLHS is associated with familial

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_16

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p­ atterns of inheritance and suspected to involve multiple genetic mutations. While this is an area of ongoing investigation, mutations in multiple specific genes (NR2F2, NKX2-5, GJA1, JAG1, NOTCH1) are associated with HLHS [11]. Several genetic syndromes, including monosomy X (Turner syndrome), Smith-Lemli-Opitz, Rubinstein-Taybi, and Jacobsen syndrome, have been associated with HLHS [11] and can be associated with worse postoperative and clinical outcomes. Due to the heterogeneous nature of the HLHS group, it is difficult to understand the embryological development; the lack of animal models also results in this knowledge gap. Fetal echocardiographic evaluation has helped understand evolution of HLHS in utero [12]. There are multiple proposed theories. Flow alteration across the mitral and aortic valves resulting from atrial septal restriction and reduced right to left flow in early gestation along with the underdevelopment of the left-sided structures has garnered some interest [13]. Arrest of the LV development in patients with severe aortic stenosis who in fetal life have dilated LV is identified as a potential candidate for fetal intervention [14, 15]. Primary mitral valve or left ventricular developmental theories resulting in poor mitral and LV development along with downstream structures has also

a

Fig. 16.1  A three-month-old infant with HLHS, mitral atresia and aortic atresia, status post-Norwood operation, and referred for pre-Glenn operation evaluation. Axial image (a) displaying the enlarged, systemic RV and comparatively small left atrium (LA); the left ventricle is nearly completely atretic with no identifiable cavity in this

been proposed, and it appears there are multiple pathways and mechanisms that ultimately result in HLHS [3]. Underdeveloped left ventricle and aorta with intact ventricular septum fall under the HLHS spectrum [4]. Anatomically the HLHS heart has normal segmental arrangement with concordant atrioventricular and ventriculoarterial connections. HLHS are broadly classified as three groups based on the degree of mitral and aortic valve dysplasia as mitral and aortic stenosis, mitral and aortic atresia, and mitral stenosis and aortic atresia. Patients with mitral atresia have slit-like severely underdeveloped left ventricles (Fig.  16.1), and those with aortic stenosis have hypoplastic LV with significant endocardial fibroelastosis (EFE) resulting from long-standing subendocardial ischemia during the cardiac development [1]. Mitral stenosis and aortic atresia variant of HLHS have high mortality risk due to suprasystemic LV and fistulous connections between the coronary arteries and the hypoplastic LV resulting in subendocardial ischemia [16]. The right ventricle is appropriately dilated and hypertrophied. The left atrium is smaller in comparison to the right atrium. Patients with intact atrial septum have high postnatal mortality, and the lack of egress across the atrial septum in these patients result in hypertensive left atrium that is

b

image. Oblique coronal image in long axis of neoaortic outflow tract (b) showing the unobstructed neoaortic (native pulmonary) outflow tract (NA) and unobstructed native-to-neoaortic connection to the severely hypoplastic native aortic root (*)

16  Left Ventricular Outflow Tract: Hypoplastic Left Heart Syndrome

a

117

b

Neo-aorta Neoaorta

I

P

DAO

c

Neo-aorta

Fig. 16.2  A 2-month-old infant with HLHS, mitral atresia and aortic atresia, and status post-Norwood operation and referred for evaluation of aortic arch obstruction and obstruction to coronary artery flow. Posterior view of three-dimensional volume rendered reconstruction image (a) of the native aortic root (*) giving rise to the left and right coronary arteries (arrows), with unobstructed proximal branches. The native-to-neoaortic connection also is

unobstructed. The neoaortic arch appears tortuous in this view and in a left lateral projection of this reconstruction (b), where the RV-PA conduit is also seen (P) on the left side of the neoaorta. There is mild narrowing at the aortic isthmus (I) in the superior-inferior dimension in this projection and in the left-right dimension on the corresponding axial images (c). DAO descending thoracic aorta

often muscularized along with abnormal pulmonary venous development [3]. Tricuspid valve dysplasia with regurgitation has been described in HLHS and tends to affect the long-term survival due to volume overloading of the systemic right ventricle, as well as with the surgical plan-

ning. Patients with aortic stenosis have larger aorta compared to those with aortic atresia where the aorta acts as a conduit for coronary flow (Figs. 16.1b and 16.2). Aortic arch is often hypoplastic to varying degrees (Fig.  16.2), and the systemic circulation is dependent on a patent

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a

b

Fig. 16.3  An 8-month-old infant with HLHS, aortic stenosis and mitral stenosis, and status post-Norwood operation followed by bidirectional Glenn procedure, referred for evaluation of the branch pulmonary arteries which were difficult to visualize on echocardiography. In contrast to images from the previous case, oblique sagittal images in the long axis of the neoaortic arch (a) show an unobstructed aortic arch (AA) without tortuosity or

obstruction. However, the left pulmonary artery (running inferiorly under the neoaortic arch) appears hypoplastic (*). Oblique coronal images in the long axis of the SVC (b) show an unobstructed SVC to right pulmonary artery (Glenn) connection, with a normal-sized proximal right pulmonary artery (R) and the left pulmonary artery (*) which gradually narrows, as seen in the other image. DAO descending thoracic aorta, S superior vena cava

ductus arteriosus [13]. Associated lesions include persistent left superior vena cava and anomalous drainage of pulmonary veins due to decompressing levocardinal vein.

modality of choice given the easy accessibility and low cost. Patients who have poor acoustic windows and those who need detailed evaluation of the vascular structures such as superior vena cava, branch pulmonary arteries (Fig. 16.3), aortic arch (Fig. 16.2 and 16.3), Glenn anastomosis, and Fontan pathway might benefit from cross-­ sectional imaging with cardiac MRI or cardiac CT [17]. Cardiac catheterization might be necessary before Glenn procedure or subsequently as it has an advantage to obtain hemodynamic data as well as its ability to intervene on the collaterals or close the Fontan fenestration. Adult Fontan patients have a unique set of problems associated with the long-standing non-physiologic flow and are at higher risk for Fontan failure, thrombotic complications, protein-losing enteropathy, etc., and proactive evaluation for these problems helps with better management [10, 18].

Diagnosis Diagnosis of HLHS is usually made either pre- or postnatally by echocardiography. The hypoplastic left-sided structures are noticeable on fetal echocardiogram. Full anatomic details including the information about the atrial septum, pulmonary veins, aortic arch, and presence of EFE can be obtained on fetal echocardiography. Postnatal echocardiogram is diagnostic as well as provides the physiologic and hemodynamic information following postnatal transition [13]. Additional imaging is rarely necessary in the neonatal period. Patients with suspected coronary anomalies or associated cardiac lesions might benefit from a cardiac CT given the short scan time and can be performed without sedation in these prostaglandin-­ dependent patients. Immediate postnatal cardiac catheterization with balloon septostomy might be needed in patients with intact atrial septum to improve pulmonary venous return. HLHS patients undergoing staged surgical procedures will need serial close follow-ups; echocardiography still remains the diagnostic

 ardiac CT Technique and Patient C Preparation The patient preparation and sequence planning are discussed in the earlier chapters. Iso-osmolar, nonionic, and water-soluble contrast agents are preferred. The usual total contrast dose is 1.5–2 ml/kg (maximum contrast dose of 130–150 ml in adults). The contrast medium is usually administered

16  Left Ventricular Outflow Tract: Hypoplastic Left Heart Syndrome

using a dual-head power injector. The injection rate is determined by the size of the intravenous (IV) catheter, and a rate of 0.8–1.2 ml/sec chased by a saline bolus is appropriate for neonates with a 24G IV.  Automated bolus tracking technique or visual monitoring with manual triggering can be used after contrast injection. Average scan delay of 4 seconds from the trigger can be used but might need adjustment based on the heart rate. The site of peripheral IV placement needs to be tailored based on the structure of interest. Prospective EKG-triggering techniques help lower the radiation dose. Patients with MRI-incompatible hardware might be better cardiac CT candidates. Retrospective sequences can be utilized to obtain functional CT that can help estimate ventricular size and function especially in subjects who have poor echocardiographic windows. Imaging of the Fontan pathway is technically challenging due to unique Fontan hemodynamics, and flow streaming patterns, inadequate contrast opacification of the Fontan pathway or branch pulmonary arteries by traditional pulmonary embolus CT protocols results in false-­positive diagnosis of a thrombus or a non-diagnostic study. A biphasic CT angiography with a single-site injection via an adequate-­ sized peripheral IV along with two acquisition phases that are about 60–70  seconds apart to visualize the entire systemic venous and pulmonary arterial pathways is ideal; Fontan pathway and pulmonary artery imaging using two IV sites with simultaneous injection is also useful [19, 20]. IV sizes greater than 22 g are better for contrast injection in Fontan patients. It is important to prepare the Fontan patients ahead of time to avoid contrast-induced renal injury. Radiation reduction techniques should be utilized to reduce the cumulative radiation dose.

Management Detailed description of managing HLHS patients from the prenatal all the way to the adults is beyond the scope of this chapter; there are excellent resources that the reader can access for clear understanding [10, 18]. Prostaglandin infusion is initiated as soon as the diagnosis is confirmed and is maintained until the initial surgery. Initial surgi-

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cal treatment is performed in the neonatal period with goals to achieve unobstructed right ventricle to aorta connection, limiting pulmonary blood flow using a modified BT shunt or Sano shunt, and relieve pulmonary venous obstruction. Glenn anastomosis is performed around 4–6 months of age with an idea to unload the systemic right ventricle. Fontan completion is performed after 3 years of age where the systemic venous return is routed to the pulmonary arteries directly without a subpulmonary ventricle; as such the systemic venous flow is passive [2, 3]. Interstage period between the first and second surgeries is associated with a second higher risk of mortality, and as such close interstage monitoring and hospitalization of high-risk patients before Glenn procedure are recommended [16]. High-risk HLHS patients are palliated using hybrid stage 1 approach followed by comprehensive stage 2. Cardiac transplantation is considered in higher-risk patients that are not candidates for single-ventricle palliation, and transplantation comes with its own set of issues and complications [2].

Outcome The overall outcomes for HLHS have improved over time with each iteration of the surgical technique as well as routine interstage monitoring. The Society of Thoracic Surgeons Congenital Heart Database shows Norwood survival among >100 congenital heart programs in the United States and Canada is 86.3% [21]. Certain individual centers report greater than 95% survival. The current interstage mortality is about 5.3% [22]. Perioperative mortality for Glenn and Fontan procedures has decreased over time. The estimation of long-term outcomes of Fontan population spans up to 35  years, with the ANZFR (Australia and New Zealand Fontan Registry) reporting a 62% survival over that time frame [10, 23]. A recent single-center study reported long-term survival with a Fontan circulation of 94% at 1 year, 90% at 10 years, 85% at 15 years, and 74% at 20  years post-Fontan completion [24]. Older Fontan techniques have worse long-­ term outcomes and have been falling out of favor for newer modifications. The long-term survival

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of HLHS patients is associated with late morbidity and thus warrants lifetime care by experienced groups [18]. Improvements and modifications of the surgeries have improved survival for these once universally lethal diagnoses [10, 25].

References 1. Anderson RH, Spicer DE.  Anatomic considerations in the functionally univentricular heart. In: Gi W, editor. Anderson’s pediatric cardiology. Philadelphia: Elsevier; 2020. p. 1245–59. 2. Lang P, Fyler DC.  Hypoplastic left heart syndrome, mitral atresia, and aortic atresia. In: Keane JF, Lock JE, Fyler DC, editors. Nadas’ pediatric cardiology. Philadelphia: Saunders; 2006. 3. Rychik J. Hypoplastic left heart syndrome. In: Fetal cardiovascular imaging a disease-based approach. Philadelphia: Elsevier/Saunders; 2012. p. 232–50. 4. Tchervenkov CI, Jacobs JP, Weinberg PM, et  al. The nomenclature, definition and classification of hypoplastic left heart syndrome. Cardiol Young. 2006;16(4):339–68. 5. Anderson RH, Spicer DE, Crucean A. Clarification of the definition of hypoplastic left heart syndrome. Nat Rev Cardiol. 2021. 6. Lev M.  Pathologic anatomy and interrelationship of hypoplasia of the aortic tract complexes. Lab Investig. 1952;1(1):61–70. 7. Noonan JA, Nadas AS. The hypoplastic left heart syndrome; an analysis of 101 cases. Pediatr Clin N Am. 1958;5(4):1029–56. 8. Liu Y, Chen S, Zühlke L, et al. Global birth prevalence of congenital heart defects 1970-2017: updated systematic review and meta-analysis of 260 studies. Int J Epidemiol. 2019;48(2):455–63. 9. Norwood WI, Lang P, Hansen DD. Physiologic repair of aortic atresia-hypoplastic left heart syndrome. N Engl J Med. 1983;308(1):23–6. 10. Rychik J, Atz AM, Celermajer DS, et al. Evaluation and management of the child and adult with fontan circulation: a scientific statement from the american heart association. Circulation 2019; CIR0000000000000696. 11. Pierpont ME, Brueckner M, Chung WK, et  al. American Heart Association Council on cardiovascular disease in the young; council on cardiovascular and stroke nursing; and council on genomic and precision medicine. Genetic basis for congenital heart disease: revisited: a scientific statement from the American Heart Association. Circulation. 2018;138(21):653–711. 12. Allan LD, Sharland G, Tynan MJ. The natural history of the hypoplastic left heart syndrome. Int J Cardiol. 1989;25(3):341–3.

S. C. Uppu and M. D. Patel 13. Goldberg D, Rychik J.  Hypoplastic left heart syndrome. In: Lai WW, Mertens LL, Cohen MS, Geva T, editors. Echocardiography in pediatric and congenital heart disease: from fetus to adult. Oxford: Wiley; 2016. p. 357–81. 14. Friedman KG, Sleeper LA, Freud LR, et al. Improved technical success, postnatal outcome and refined predictors of outcome for fetal aortic valvuloplasty. Ultrasound Obstet Gynecol. 2018;52(2):212–20. 15. Pickard SS, Wong JB, Bucholz EM, et al. Fetal aortic valvuloplasty for evolving hypoplastic left heart syndrome: a decision analysis. Circ Cardiovasc Qual Outcomes. 2020;13(4):006127. 16. Tweddell JS, Hoffman GM, Ghanayem NS, Frommelt MA, Mussatto KA, Berger S.  Hypoplastic left heart syndrome. In: Allen HD, Shaddy RE, Penny DJ, Feltes TF, Cetta F, editors. Moss and Adams’ heart disease in infants, children, and adolescents: including the fetus and young adult. Philadelphia: Lippincott Williams & Wilkins; 2016. p. 1125–62. 17. Lu JC, Dorfman AL, Attili AK, Ghadimi Mahani M, Dillman JR, Agarwal PP.  Evaluation with cardiovascular MR imaging of baffles and conduits used in palliation or repair of congenital heart disease. Radiographics. 2012;32(3):E107–27. 18. Stout KK, Daniels CJ, Aboulhosn JA, et  al. 2018 AHA/ACC guideline for the management of adults with congenital heart disease: a report of the american college of cardiology/american heart association task force on clinical practice guidelines. Circulation. 2019;139(14):698–800. 19. Boggs R, Dibert T, Co-Vu J, DeGroff C, Quinn N, Chandran A. Optimized computed tomography angiography protocol for the evaluation of thrombus in patients with Fontan anatomy. Pediatr Cardiol. 2020;41(8):1601–7. 20. Ghadimi Mahani M, Agarwal PP, Rigsby CK, et al. CT for assessment of thrombosis and pulmonary embolism in multiple stages of single-ventricle palliation: challenges and suggested protocols. Radiographics. 2016;36(5):1273–84. 21. Tweddell JS, Bronicki RA, Salvin JW, Naim MY, Riley CM, Wernovsky G. Fontan pathway from birth through early childhood. In: Gi W, editor. Anderson’s pediatric cardiology. Philadelphia: Elsevier; 2020. p. 1273–306. 22. Anderson JB, Brown DW, Lihn S, et  al. Power of a learning network in congenital heart disease. World J Pediatr Congenit Heart Surg. 2019;10(1):66–71. 23. Australia and New Zealand Fontan Registry: REPORT 2018. 2019. 24. Downing TE, Allen KY, Glatz AC, et  al. Long-term survival after the Fontan operation: Twenty years of experience at a single center. J Thorac Cardiovasc Surg. 2017;154(1):243–253.e2. 25. Metcalf MK, Rychik J.  Outcomes in hypoplas tic left heart syndrome. Pediatr Clin N Am. 2020;67(5):945–62.

Double-Outlet Right Ventricle

17

Laura Schoeneberg and Dilachew A. Adebo

Introduction

Embryology and Anatomy

Double-outlet right ventricle (DORV) comprises 1–3% of all congenital heart defects [1]. DORV has a prevalence of 127 in 1,000,000 live births [2]. There is no standard surgical technique for anatomic correction of DORV as there are multiple variants depending on the relationship of the ventricular septal defect (VSD) to the great arteries. For patients with DORV, surgical repair may be biventricular and include baffling the intraventricular shunt, a right ventricular to pulmonary artery (RV-PA) conduit, or arterial switch. Patients may also have a univentricular repair depending on the size of the ventricles, remoteness of the ventricular septal defect, or chordal attachments of the atrioventricular leaflets.

DORV is formed by an abnormal connection between the ventricles and great vessels or ventricular arterial connection [3]. This occurs when there is no fibrous continuity between the mitral and aortic valve. However a recent study by Ebadi found that in 20% DORV there can be fibrous continuity between the arterial and atrioventricular valves [4]. In some cases of DORV, there may be dextro-malposition of the great arteries (Taussig-Bing) (Fig. 17.1). In this case the aorta and greater than 50% of the pulmonary artery would arise from the right ventricle. There is conal septum in the right ventricle present under one of both great arteries in DORV. The ventricular septal defect (VSD) helps define the type of DORV as well by its relationship to the great arteries. If the VSD is near the pulmonary valve with the upper margin above the conal septum, then it is classified as subpulmonary (Taussig-Bing malformation type) [5]. If it is under the aortic valve, then it is subaortic [6]. If the VSD is far away from both great arteries, then it is classified as remote or noncommitted, and it is doubly committed if it is below both great arteries [3, 6]. DORV may rarely be associated with atrioventricular canal defects or heterotaxy syndrome [7]. DORV can occur in patients with any type of atrial or ventricular arrangement, and careful consideration to evaluate the a­ trioventricular valve attachments must

L. Schoeneberg Children’s Heart Institute, Division of Pediatric Cardiology, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected] D. A. Adebo (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_17

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b

a

Ao

PA Ao

RV

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Fig. 17.1  An Infant with DORV. Cardiac CT with coro- malposed great arteries. Coronal reconstruction (a) and nal reconstructed image demonstrating double-outlet right three-dimensional volume rendered reconstruction (b) ventricle with both the aorta (Ao) and pulmonary artery (PA) arising from the right ventricle (RV) with dextro-­

be made as they can be straddling and alter surgical repair [7].

Diagnosis The diagnosis of DORV is generally made by two-dimensional echocardiography and Doppler examination. Echocardiography demonstrates how the great arteries arise in relation to the ventricular septal defect (VSD) in DORV. The location of the VSD in DORV is very important as this can determine the physiology of the patient in addition to the type of surgical repair. Multiple types of imaging modalities may be used including echocardiography, cardiac angiography, and magnetic resonance imaging [6]. Due to the complex nature of the VSD in relation to the outflow tracts, cardiac CT is used as well as 3D reconstructions [8, 9]. A study by Chen et  al. documented the accuracy of 3D CT for diagnosing DORV type as 88–100% versus echocardiography 71–94% [6]. The clinical presentation of patient(s) with DORV, normally related great

arteries and no pulmonary stenosis, is usually of a large ventricular septal defect. Many now are prenatally diagnosed, but if not usually present after a few weeks postnatally. However, they may occasionally have coarctation or interrupted aortic arch and present with low cardiac output heart failure early in life [7]. With Taussig-Bing, they will have transposition physiology. In patients with pulmonary stenosis, they will present similar to tetralogy of Fallot patients and may have cyanotic episodes depending on the degree of stenosis. Low radiation dose cardiac CT can be done in newborns and infants and can provide key information with 3D reconstructions of the VSD position in DORV that can alter the surgical repair [9]. Coronary artery variations must be well delineated prior to surgical intervention for patients in DORV (Fig. 17.2). Cardiac CT is an important diagnostic tool for determining the courses and origins of the coronary arteries. A study by Goo states that in patients with tetralogy of Fallot, DORV-type dual-source cardiac CT was 96.9% accurate in determining the coronary anatomy [10].

17  Double-Outlet Right Ventricle

AO

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MPA LCA RV

RCA

LV RV

RV

Fig. 17.3  A patient with DORV who had a retrospective gated cardiac CT performed for evaluation of intraventricular baffle closure and biventricular repair. RV right ventricle, LV left ventricle Fig. 17.2  An infant with DORV. Cardiac CT volume rendered reconstruction shows dextro-malposed great vessels with anomalous coronaries. The left coronary artery courses over the pulmonary outflow tract. AO aorta, MPA main pulmonary artery

 atient Preparation, Contrast P Medium, and Cardiac CT Technique The patient should be positioned in the scanner at its isocenter with the arms positioned over the patient’s head and the electrocardiographic electrodes and any other tubing, wires, or equipment positioned out of the desired thoracic field of view to both minimize radiation dose and artifact. Iso-osmolar, non-ionic, and water-soluble contrast agent is preferred in neonates. The usual total contrast dose is 1.5–2 ml/kg of body weight in young infants. The contrast medium is usually administered by using dual-head power injector at injection rate of 0.8–1 ml/sec in neonatal scan. An equal-sized bolus of saline solution (sodium chloride solution) is injected at the same flow rate to reduce high-density contrast artifact (streak artifact). Automated bolus tracking technique or visual monitoring with manual starting can be used after contrast injection. Average scan delay of 4 seconds is used to evaluate right-sided heart structures, and a scan delay of 5–8  seconds is used to evaluate left-sided heart structures. After arterial switch operation, biventricular contrast

injection or triphasic contrast injection technique is used to delineate both right-sided and left-­ sided structures (pulmonary arteries, coronary arteries, and aortic root). The rapid image acquisition technique has eliminated or significantly reduced the need for sedation and anesthesia in those unable to cooperate with breath hold. The preferred cardiac CT technique is prospective gated cardiac CT using modern dual-­source multidetector CT scanners. Retrospective gated approach is used for ventricular function evaluation [11] or coronary artery evaluation with fast heart rate [12–19]. For patients with DORV, the retrospective gated technique is also used to evaluate the heart in systole and diastole to look at ventricular volumes before and after accounting for the intraventricular baffle (Fig. 17.3).

Management Approach Prenatal diagnosis of DORV can help improve postnatal management as some patients may have aortic arch obstruction or malposed great vessels. Surgical approach significantly varies based on the type of DORV.  For most DORV patients with VSD physiology, the surgical approach is to tunnel the left ventricle to one of the outflows to create a biventricular repair. If it can be done with the aorta, then no further repair

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is needed. In cases such as Taussig-Bing malformation, an arterial switch procedure, Rastelli or Nikaidoh, with aortic translocation may need to be performed [5]. Patients must go down the single-­ventricle pathway if there will not be sufficient biventricular volumes with baffling [18]. The single-ventricle-pathway patients may require a pulmonary artery band or right ventricular to pulmonary artery conduit, Sano shunt (Fig. 17.4), and subsequent bidirectional Glenn or Fontan procedure (Fig.  17.5). The tricuspid valve may be affected if the VSD is an inlet VSD [19]. The determination of which pathway is the ventricular septal defect relation to the right ventricle and if it is aligned with the outflow tracks [7, 19]. In a study by Villemain et al., the VSD had to be enlarged in 50% of the cases [3]. CT plays an important role in the management. Postprocessing abilities now include being able to segment out the myocardium and create 3D images (Figs. 17.6 and 17.7) [5]. 3D reconstructions from cardiac CT can help improve the surgeon’s understanding of the space needed to connect the ventricle to the outflow in addition to allowing them to simulate the surgical repair [7, 9]. The 3D reconstruction can help determine if the surgical approach can be

a

Sano

Ao

performed through the right atrium and tricuspid valve or if a ventriculotomy needs to be performed [5].

Outcome The long-term survival rates for patients with DORV following surgical correction are excellent. Complications associated with DORV used to be approximately 20% if they had a biventricular repair and 100% reoperation rate at 10 years; however if the patients had a noncommitted VSD, the mortality rate was 50% [19]. Patients who received a Fontan had similar survival rates, but reoperation was only 30% at 10  years [19]. A more recent study documented a 2-year mortality of 19% in the entire group of 36 patients with 21% in the biventricular repair group and 17% in the univentricular group, with patients having atrioventricular septal defect at higher risk of poor outcomes [3]. Of the survivors in the biventricular group, 42% underwent reoperation at 2 years, with the primary operation being subaortic stenosis [3]. There was no early reoperation in the univentricular group and only one late reoperation [3]. Other studies have documented one

b

PA

Ao Sano

VSD

LV

RV

RV

Fig. 17.4  An infant with DORV and pulmonary atresia who undergone right ventricular to pulmonary artery conduit placement (Sano conduit). Cardiac CT was performed to plan the next surgical procedure. Coronal reconstructed

image (a) and three-dimensional volume rendered reconstruction (b) show large subpulmonary VSD and Sano conduit. AO aorta, PA pulmonary outflow, VSD ventricular septal defect, RV right ventricle, LV left ventricle

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b

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Tortuous aorta

SCPA PA

RPA

LPA

Ao

RV

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Fig. 17.5  An infant with DORV with malposed great arteries after a Kawashima procedure. Cardiac CT with coronal reconstructed image (a), axial reconstructed image (b), and delayed venous phase acquisition (c) showing tortuous aortic arch and arch branches and patent superior cavopulmonary anastomosis. Azygous continuation in the setting of interrupted inferior vena cava was

also seen. SVC superior vena cava, IVC inferior vena cava, AZ azygous vein, RPA right pulmonary artery, LPA left pulmonary artery, AO native aortic root, PA pulmonary artery (neoaortic root), DAO descending thoracic aorta, RV right ventricle, SCPA superior cavopulmonary anastomosis

early and one late mortality with others as high as 11% in hospital mortality and 16.6% late mortality [21, 22]. The complicated part of DORV is that the surgical repairs can vary significantly based on the type as to whether they require an

intraventricular baffle, arterial switch, or a conduit [20]. The most common cause for reintervention is left ventricular outflow tract obstruction or right ventricular outflow tract obstruction [22].

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a

b

AO MPA

AO MPA

RV RV

LV

c

AO

MPA

Fig. 17.6  An infant with double-outlet right ventricle, dextro-malposed great arteries, pulmonary stenosis, and remote ventricular septal defect. Modified sagittal reconstructed image of right ventricular outflow tract (a) and volume rendered reconstruction (b) showing both great

arteries arising from the right ventricle. Computer-assisted virtual model (c) shows route of virtual conduit from remote ventricular septal defect to aortic outflow (A). RV right ventricle, AO aortic root, MPA main pulmonary artery

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a

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AO

MPA

RV

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DAO

Fig. 17.7  An infant with double-outlet right ventricle, dextro-malposed great arteries, remote ventricular septal defect, and subaortic narrowing due to deviated conal septum (arrowhead). Cardiac CT also shows hypoplastic aortic arch (white arrow). Computer-assisted virtual model

shows virtual patch (black arrow) to help in surgical planning. Coronal (a), sagittal (b), volume rendered reconstruction (c), and virtual model (d). RV right ventricle, LV left ventricle, AO aorta, MPA main pulmonary artery, DAO descending thoracic aorta

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References 1. Beegle RD, Mastin ST, Chandran A. Case of double-­ outlet right ventricle after repair with pulmonary arteriovenous malformations using cardiac CT.  J Cardiovasc Comput Tomogr. 2014;8(5):401–3. https://doi.org/10.1016/j.jcct.2014.05.003. 2. Hoffman JIE, Kaplan S. The incidence of congenital heart disease. J Am Coll Cardiol. 2002;39(12):1890– 900. https://doi.org/10.1016/s0735-­1097(02)01886-­7. 3. Villemain O, Bonnet D, Houyel L, Vergnat M, Ladouceur M, Lambert V, Jalal Z, Vouhe P, Belli E.  Double-outlet right ventricle with noncommitted ventricular septal defect and 2 adequate ventricles: is anatomical repair advantageous? Semin Thorac Cardiovasc Surg. 2016;28(1):69–77. https://doi. org/10.1053/j.semtcvs.2016.01.007. 4. Ebadi A, Spicer DE, Backer CL, Fricker FJ, Anderson RH. Double-outlet right ventricle revisited. J Thorac Cardiovasc Surg. 2017;154(2):598–604. https://doi. org/10.1016/j.jtcvs.2017.03.049. 5. Dydynski PB, Kiper C, Kozik D, Keller BB, Austin E, Holland B.  Three-dimensional reconstruction of intracardiac anatomy using CTA and surgical planning for double outlet right ventricle: early experience at a tertiary care congenital heart center. World J Pediatr Congenit Heart Surg. 2016;7(4):467–74. https://doi.org/10.1177/2150135116651399. 6. Chen S-J, Lin M-T, Liu K-L, Chang C-I, Chen H-Y, Wang J-K, Lee W-J, Tsang Y-M, Li Y-W. Usefulness of 3D reconstructed computed tomography imaging for double outlet right ventricle. J Formos Med Assoc. 2008;107(5):371–80. https://doi.org/10.1016/ s0929-­6646(08)60102-­3. 7. Bharucha T, Hlavacek AM, Spicer DE, Theocharis P, Anderson RH. How should we diagnose and differentiate hearts with double-outlet right ventricle? Cardiol Young. 2017;27(1):1–15. https://doi.org/10.1017/ S1047951116001190. 8. Dodge-Khatami J, Adebo DA. Evaluation of complex congenital heart disease in infants using low dose cardiac computed tomography. Int J Cardiovasc Imaging. 2021; https://doi.org/10.1007/s10554-­020-­02118-­7. 9. Bhatla P, Tretter JT, Chikkabyrappa S, Chakravarti S, Mosca RS.  Surgical planning for a complex double-outlet right ventricle using 3D printing. Echocardiography. 2017;34(5):802–4. https://doi. org/10.1111/echo.13512. 10. Goo HW. Coronary artery anomalies on preoperative cardiac CT in children with tetralogy of Fallot or Fallot type of double outlet right ventricle: comparison with surgical findings. Int J Cardiovasc Imaging. 2018;34(12):1997– 2009. https://doi.org/10.1007/s10554-­018-­1422-­1. 11. Goo HW, Park IS, Ko JK, Kim YH, Seo DM, Park JJ.  Computed tomography for the diagnosis of congenital heart disease in pediatric and adult patients. Int J Cardiovasc Imaging. 2005;21(2–3):347–65; discussion 367. https://doi.org/10.1007/s10554-­004-­4015-­0. 12. Leschka S, Oechslin E, Husmann L, Desbiolles L, Marincek B, Genoni M, Pretre R, Jenni R, Wildermuth

L. Schoeneberg and D. A. Adebo S, Alkadhi H.  Pre- and postoperative evaluation of congenital heart disease in children and adults with 64-section CT.  Radiographics. 2007;27(3):829–46. https://doi.org/10.1148/rg.273065713. 13. Han BK, Lindberg J, Grant K, Schwartz RS, Lesser JR.  Accuracy and safety of high pitch computed tomography imaging in young children with complex congenital heart disease. Am J Cardiol. 2011;107(10):1541–6. https://doi.org/10.1016/j. amjcard.2011.01.065. 14. Schicchi N, Fogante M, Esposto Pirani P, Agliata G, Basile MC, Oliva M, Agostini A, Giovagnoni A.  Third-generation dual-source dual-energy CT in pediatric congenital heart disease patients: state-of-­ the-art. Radiol Med. 2019;124(12):1238–52. https:// doi.org/10.1007/s11547-­019-­01097-­7. 15. Paul JF, Rohnean A, Sigal-Cinqualbre A.  Multidetector CT for congenital heart patients: what a paediatric radiologist should know. Pediatr Radiol. 2010;40(6):869–75. https://doi.org/10.1007/ s00247-­010-­1614-­x. 16. Hu XH, Huang GY, Pa M, Li X, Wu L, Liu F, Jia B, Li GP. Multidetector CT angiography and 3D reconstruction in young children with coarctation of the aorta. Pediatr Cardiol. 2008;29(4):726–31. https:// doi.org/10.1007/s00246-­008-­9226-­z. 17. Cheng Z, Wang X, Duan Y, Wu L, Wu D, Chao B, Liu C, Xu Z, Li H, Liang F, Xu J, Chen J. Low-dose prospective ECG-triggering dual-source CT angiography in infants and children with complex congenital heart disease: first experience. Eur Radiol. 2010;20(10):2503–11. https://doi.org/10.1007/ s00330-­010-­1822-­7. 18. Booij R, Dijkshoorn ML, van Straten M, du Plessis FA, Budde RP, Moelker A, Krestin GP, Ouhlous M.  Cardiovascular imaging in pediatric patients using dual source CT. J Cardiovasc Comput Tomogr. 2016;10(1):13–21. https://doi.org/10.1016/j. jcct.2015.10.003. 19. Yim D, Dragulescu A, Ide H, Seed M, Grosse-­ Wortmann L, van Arsdell G, Yoo SJ. Essential modifiers of double outlet right ventricle: revisit with endocardial surface images and 3-dimensional print models. Circ Cardiovasc Imaging. 2018;11(3):e006891. https://doi.org/10.1161/CIRCIMAGING.117.006891. 20. Backer CL. Double outlet right ventricle: where are we now? Semin Thorac Cardiovasc Surg. 2016;28(1):79– 80. https://doi.org/10.1053/j.semtcvs.2016.03.004. 21. Lu T, Li J, Hu J, Huang C, Tan L, Wu Q, Wu Z. Biventricular repair of double-outlet right ventricle with noncommitted ventricular septal defect using intraventricular conduit. J Thorac Cardiovasc Surg. 2020;159(6):2397–403. https://doi.org/10.1016/j. jtcvs.2019.07.084. 22. Barbero-Marcial M, Tanamati C, Atik E, Ebaid M. Intraventricular repair of double-outlet right ventricle with noncommitted ventricular septal defect: advantages of multiple patches. J Thorac Cardiovasc Surg. 1999;118(6):1056–67. https://doi.org/10.1016/ s0022-­5223(99)70102-­9.

Dextro-Transposition of the Great Arteries

18

Laura Schoeneberg and Dilachew A. Adebo

Introduction

Embryology and Anatomy

Dextro-transposition of the great arteries (D-TGA) is the second commonest cyanotic heart defect, accounting for 5% of all congenital heart defects. D-TGA has a prevalence of 20–30 in 100,000 live births, with a 2:1 male predominance. Arterial switch operation (ASO) has become the standard surgical technique for anatomic correction of D-TGA [1, 2]. For patients with D-TGA, intact ventricular septum, and without any other cardiac defects, ASO is typically performed in the first 1–2 weeks of life.

It is hypothesized that the morphogenesis of D-TGA is due to the abnormal growth and development of the bilateral subarterial conus. In normal cardiac development, the subaortic conus and subpulmonary conus are present in the first month of gestation as the great arteries are positioned superior to the right ventricle. Typically, the subaortic conus is resorbed at approximately 30–34  days into gestation, which allows for migration of the aortic valve inferiorly and posteriorly into its normal position above the left ventricle. Subaortic conal resorption also leads to the characteristic fibrous continuity between the mitral and aortic valve within the left ventricle. The pulmonary valve retains its association with the right ventricle due to the persistence of the subpulmonary conus. In D-TGA, however, the subpulmonary conus is resorbed, which allows for posterior migration of the pulmonary valve and the development of fibrous continuity between the pulmonary and mitral valve. The unabsorbed subaortic conus forces the aortic valve anteriorly, where it abnormally engages with the morphologic right ventricle. The range in the size and orientation of the subaortic conus is thought to create much of the variability of the coronary arteries’ origins and course. In normal cardiac anatomy, the aorta is positioned posterior and to the right of the main

L. Schoeneberg Children’s Heart Institute, Division of Pediatric Cardiology, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected] D. A. Adebo (*) Children’s Heart Institute, Division of Pediatric Cardiology, Non-Invasive Cardiac Imaging, Children’s Memorial Hermann Hospital, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA e-mail: [email protected]

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 D. A. Adebo (ed.), Pediatric Cardiac CT in Congenital Heart Disease, https://doi.org/10.1007/978-3-030-74822-7_18

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a

b RV AO

PA LV

RA LV RV

ASD LA

Fig. 18.1  Cardiac CT multiplanar-reconstructed image in the ventricular outflow tracts showing the aorta arising from the right ventricle and pulmonary artery arising from the left ventricle (a). Moderate-sized secundum atrial sep-

tal defect in four-chamber view (b). Ao Aorta, PA pulmonary artery, RV right ventricle, LV left ventricle, ASD secundum atrial septal defect

p­ulmonary artery. Also, the morphologic right ventricle has a large outflow tract component known as the infundibulum. In D-TGA, the aorta arises from the right ventricle and the pulmonary artery from the left ventricle (Fig. 18.1).

and postoperative D-TGA patients (Figs.  18.2 and 18.3). Cardiac CT is also increasingly used in postoperative evaluation of D-TGA to assess pulmonary artery stenosis, coronary artery stenosis, neoaortic root dilatation, and aortic arch evaluation (Figs. 18.3 and 18.4).

Diagnosis The diagnosis of D-TGA is generally made by two-dimensional echocardiography and Doppler examination. Echocardiography shows great artery that branches into the left and right pulmonary arteries arising from the posterior left ventricle. Echocardiography also demonstrates the presence or absence of other commonly associated cardiac anomalies such as a ventricular septal defect (VSD), left ventricular outflow tract obstruction, atrioventricular valve abnormality, aortic arch obstruction, and the coronary artery anatomy. Coronary artery variations must be well delineated prior to surgical intervention. Cardiac CT is very important for elucidating coronary arteries’ courses and origins and is used, at times, for patients with coronary anatomy that cannot be determined confidently with echocardiography [3, 4]. Cardiac CT delineates coronary artery anatomy in both preoperative

 atient Preparation, Contrast P Medium, and Cardiac CT Technique An iso-osmolar, non-ionic, and water-soluble contrast agent is preferred in neonates. The usual total contrast dose is 1.5–2 ml/kg of body weight in young infants. The contrast medium is usually administered by using dual-head power injector at injection rate of 0.8–1 ml/sec in neonatal scan. An equal-sized bolus of saline solution (sodium chloride solution) is injected at the same flow rate to reduce high-density contrast artifact (streak artifact). Automated bolus tracking technique or visual monitoring with manual starting can be used after contrast injection. An average scan delay of 4 seconds is used to evaluate right-sided heart structures, and a scan delay of 5–8 seconds is used to evaluate left-sided heart structures. After arterial switch operation, biventricular contrast injec-

18  Dextro-Transposition of the Great Arteries

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AAO LPA

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Fig. 18.2  Infant with D-TGA after arterial switch operation. Cardiac CT axial image showing branch pulmonary arteries anterior to ascending aorta after arterial switch operation with LeCompte maneuver (a). AAo ascending

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aorta, RPA right pulmonary artery, LPA left pulmonary artery, DAO descending thoracic aorta. Right and left coronary arteries are seen on volume-rendered reconstructed image as indicated by arrows (b)

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Fig. 18.3  Volume-rendered images of cardiac CT showing unusual coronary artery anatomy with single coronary artery system arising via the common ostium (arrow) (a) and left anterior descending coronary artery arising from

the right coronary artery (b). RCA right coronary artery, LAD left anterior descending coronary artery, LMCA left main coronary artery, Ao aortic root, PA pulmonary artery, RV right ventricle, LV left ventricle

tion or triphasic contrast injection technique is used to delineate both right-sided and left-sided structures (pulmonary arteries, coronary arteries, and aortic root). The rapid image acquisition technique has eliminated or significantly reduced the need for sedation and anesthesia in those unable to cooperate with breath hold. The preferred cardiac CT technique is prospective gated cardiac CT using modern dual-­ source multidetector CT scanners. Retrospective gated approach is used for ventricular function

evaluation or coronary artery evaluation with fast heart rate [5–15].

Management Approach Prenatal diagnosis of D-TGA improves survival by making timely decision to start prostaglandin infusion and the need for a balloon atrial septostomy [16–18]. The initial postnatal management is focused on ensuring adequate systemic oxygenation.

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a

b

TAR

TAR

DAO DAO

Fig. 18.4  Neonate with dextro-transposition of great arteries and aortic arch hypoplasia. Cardiac CT in parasagittal reconstructed view (a) and volume-rendered

reconstruction (b) showing mildly hypoplastic transverse aortic arch. TAR transverse aortic arch, DAO descending thoracic aorta

The definitive corrective surgery is arterial switch operation which replaced the earlier atrial switch procedures developed by Mustard and Senning. In patients with D-TGA and a ventricular septal defect (VSD), the preferred procedure is ASO and VSD closure. In patients with D-TGA, VSD, and significant left ventricular outflow tract obstruction (due to valvular, subvalvar, or multilevel obstruction), the Rastelli procedure is an alternative surgical approach that may be considered. Both the ASO and Rastelli procedures are surgical anatomic corrections resulting in a morphologic left ventricle as the systemic ventricle. In contrast, atrial switch procedures (also referred to as the Mustard and Senning procedures) involve rerouting venous return in the atria, resulting in a systemic right ventricle. Atrial switch procedures are now only rarely performed. The LeCompte maneuver, first described in 1981, is widely utilized when performing the ASO. This surgical technique places the bifurcation of the pulmonary arteries anterior to the aorta so that the left and right pulmonary arteries straddle the ascending aorta. This allows for improved orientation of the branch pulmonary arteries and reduces the tension that is created from the anterior translocation of the pulmonary arterial root. The use of this maneuver decreases

the risk of subsequent pulmonary artery stenosis and lowers reintervention rates. The Rastelli procedure, first described in 1969, is typically performed in patients with D-TGA associated with a large VSD and LVOT obstruction. The Rastelli procedure is preferred over the ASO for some patients because it provides superior and more durable relief of LVOT obstruction. The decision to perform the Rastelli procedure rather than the ASO with LVOT reconstruction is largely based on the nature of the LVOT obstruction and the status of the pulmonary (neo-aortic) valve. The Rastelli procedure involves baffling the LVOT through the VSD, which closes the VSD and directs oxygenated blood from the left ventricle into the aorta [19–25]. Atrial switch procedures including the Mustard and Senning procedures convert the parallel circulations of D-TGA into a circulation in series, thereby correcting cyanosis. However, they do not correct the underlying ventriculoarterial discordance of the aorta arising from the right ventricle and the pulmonary artery from the left ventricle (Fig. 18.5). In both procedures, an intra-­atrial baffle is created to divert the deoxygenated systemic venous return through the mitral valve to the left ventricle, and into the pulmonary circulation via the pulmonary artery. Simultaneously, the baffle directs oxygenated pulmonary venous return across the tricuspid valve to the right ventricle and

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RV RA PVP

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d SVC AO

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Fig. 18.5 Patient after arterial switch operation for dextro-­transposition of great arteries. Cardiac CT axial (a), modified coronal (b), and volume-rendered reconstructions (c, d) showing patent pulmonary venous pathway (PVP) but significant narrowing of superior vena

cava baffle (white arrow) and disruption of the superior vena cava baffle at its right atrial junction (black arrow). RV systemic right ventricle, LV pulmonary left ventricle, PVP pulmonary venous pathway, SVC superior vena cava, IVC inferior vena cava

subsequently to the aorta and the systemic circulation. Superior baffle obstruction is commonly seen after atrial switch operation (Fig. 18.5). Cardiac anomalies associated with D-TGA include ventricular septal defect, left ventricular outflow tract obstruction, coronary artery variations, atrioventricular valve abnormality (overriding or straddling tricuspid valve over the VSD), and aortic arch obstruction.

90% for unoperated patients to rates of