Loss of myocardial Hey2/Hrt2 function disrupts rightward shift of atrioventricular cushion tissue and causes tricuspid atresia.

BACKGROUND: Endocardial cushion tissue is primordia of the valves and septa of the adult heart, and its malformation causes various congenital heart diseases (CHDs). Tricuspid atresia (TA) is defined as congenital absence or agenesis of the tricuspid valve caused by endocardial cushion defects. However, little is known about what type of endocardial cushion defect causes TA. RESULTS: Using three-dimensional volume rendering image analysis, we demonstrated morphological changes of endocardial cushion tissue in developing Hey2/Hrt2 KO mouse embryos that showed malformation of the tricuspid valve, which resembled human TA at neonatal period. In control embryos, atrioventricular (AV) endocardial cushion tissues showed rightward shift to form a tricuspid valve. However, the rightward shift of endocardial cushion tissue was disrupted in Hey2/Hrt2 KO embryos, leading to the misalignment of AV cushions. We also found that muscular tissue filled up the space between the right atrium and ventricle, resulting in the absence of the tricuspid valve. Moreover, analysis using tissue-specific conditional KO mice showed that HEY2/HRT2-expressing myocardium may physically regulate the AV shift. CONCLUSION: Disruption of rightward cushion movement is an initial cue of TA phenotype, and myocardial HEY2/HRT2 is necessary for the regulation of proper alignment of AV endocardial cushion tissue.

Human Genetics of Tricuspid Atresia and Univentricular Heart.

Tricuspid atresia (TA) is a rare congenital heart condition that presents with a complete absence of the right atrioventricular valve. Because of the rarity of familial and/or isolated cases of TA, little is known about the potential genetic abnormalities contributing to this condition. Potential responsible chromosomal abnormalities were identified in exploratory studies and include deletions in 22q11, 4q31, 8p23, and 3p as well as trisomies 13 and 18. In parallel, potential culprit genes include the ZFPM2, HEY2, NFATC1, NKX2-5, MYH6, and KLF13 genes. The aim of this chapter is to expose the genetic components that are potentially involved in the pathogenesis of TA in humans. The large variability in phenotypes and genotypes among cases of TA suggests a genetic network that involves many components yet to be unraveled.

Molecular Pathways and Animal Models of Tricuspid Atresia and Univentricular Heart.

The process of valve formation is a complex process that involves intricate interplay between various pathways at precise times. Although we have not completely elucidated the molecular pathways that lead to normal valve formation, we have identified a few major players in this process. We are now able to implicate TGF-ß, BMP, and NOTCH as suspects in tricuspid atresia (TA), as well as their downstream targets: NKX2-5, TBX5, NFATC1, GATA4, and SOX9. We know that the TGF-ß and the BMP pathways converge on the SMAD4 molecule, and we believe that this molecule plays a very important role to tie both pathways to TA. Similarly, we look at the NOTCH pathway and identify the HEY2 as a potential link between this pathway and TA. Another transcription factor that has been implicated in TA is NFATC1. While several mouse models exist that include part of the TA abnormality as their phenotype, no true mouse model can be said to represent TA. Bridging this gap will surely shed light on this complex molecular pathway and allow for better understanding of the disease process.

Tricuspid Atresia with Absent Pulmonary Valve with Nearly Discontinuous Branch Pulmonary Arteries.

Absent pulmonary valve with tricuspid atresia or tricuspid stenosis (APV-TA/TS) is an extremely rare congenital heart defect associated with significant morbidity and mortality. Compared to Tetralogy of Fallot with Absent Pulmonary Valve Syndrome, branch pulmonary arteries are not typically significantly dilated. We present the case of a newborn male prenatally diagnosed APV-TA with intact ventricular septum (IVS) and nearly discontinuous branch pulmonary arteries, the surgical strategy employed, and the salient hemodynamic factors considered in the medical decision-making.

Combined tricuspid atresia- AV septal defect-a rare congenital cardiac abnormality.

INTRODUCTION: Congenital heart diseases (CHDs) are one of the most common birth defects worldwide with a prevalence of 1%. CHDs can be classified into cyanotic and acyanotic diseases based on the presence or absence of the characteristic bluish discoloration of skin and mucus membranes. A subset of cyanotic diseases is single ventricle malformations. This group of disorders comprises 1% of all CHDs. A remarkable yet rare and underreported entity of single ventricle malformations is combined tricuspid atresia (TA) and atrioventricular (AV) septal defect which is characterized by the anatomical features of both entities. Combined TA-AV septal malformation was first anatomically described in 1953 and further explored through echocardiography and cardiac catheterization in 1987 and then 1991. Since then, no studies have been documented in the literature prompting us to share our findings. METHODS: Herein we are describing a rare and underreported cardiac lesion based of a retrospective revision of medical charts at the American University of Beirut Medical Center (AUBMC) Children's Heart Center, a tertiary medical center in the Middle East RESULTS: Out of 200 cases with confirmed single ventricle physiology, we identified a few patients with characteristics of combined TA-AV septal defect. Our patients exhibited characteristic echocardiographic findings of primum ASD, VSD, atretic RAVV, and clefted LAVV. CONCLUSION: In short, TA-AV septal defect is a rare, underreported congenital malformation. Tracking our patients' clinical profiles will help improve our understanding of the prognosis of this entity. Our findings may also improve treatment modalities since replacing the left-sided valve is often overlooked if the defect is inaccurately diagnosed. In addition, such findings can help shed light on the embryological development of the rarely encountered variation of AV septal malformation.

Dichorionic Diamniotic Twin Pairs with Complex Congenital Heart Disease.

Complex congenital heart disease (CHD) in each of dichorionic diamniotic (DiDi) twin pairs is extremely rare and has not been well characterized. Four DiDi twin pairs were included in this multi-institutional case series. The congenital cardiac abnormalities noted included tetralogy of Fallot (ToF) with pulmonary atresia and collaterals (n = 1), ToF with absent pulmonary valve (n = 1), ToF (n = 2), discontinuous right pulmonary artery (RPA) (n = 1), tricuspid atresia (TA) with normally related great arteries and pulmonary valve stenosis or atresia (n = 2) and coarctation of aorta (CoA) with bicuspid aortic valve (BAV) and borderline left-sided structures (n = 1). Genetic testing was obtained on seven of the eight twins but did not reveal any causal abnormality. A comprehensive review of literature yielded another 8 DiDi twin pairs with complex CHD. The CHD noted in these twin pairs included ToF (n = 2), CoA (n = 4), corrected transposition of great arteries (ccTGA) (n = 2), truncus arteriosus (n = 2), complete common atrioventricular canal (CCAVC) (n = 2), hypoplastic left heart syndrome (HLHS) (n = 2), Shone's complex (n = 1), and hypoplastic right heart syndrome (HRHS) (n = 1). Limited genetic testing was obtained on 4 of these twins and revealed trisomy 21 in a twin pair. Conotruncal abnormalities (42%), CoA (21%), and abnormalities of the right ventricle, the right ventricular outflow tract and pulmonary arteries (17%) are more prevalent in DiDi twins with complex CHD. Clustering of these abnormalities suggests a possible genetic basis; however, genetic testing was obtained on eleven of the twins, and except for trisomy 21 in a twin pair both of whom had CCAVC, did not reveal any causal abnormality. A major direct genetic contribution is therefore unlikely and like other CHD, the underlying etiopathological basis is likely multifactorial.

The prognostic role of liver volumetry in Fontan patients.

BACKGROUND AND HYPOTHESES: High venous pressures and associated hepatic congestion are important drivers for Fontan-associated liver disease. The prognostic significance of hepatomegaly as a marker of congestion however is not well defined and is further explored in this research study. METHODS: Fontan patients who have had liver ultrasound scans were identified from the Prince Sultan Cardiac Centre Fontan Database and had their anatomic, surgical, clinical histories abstracted from the electronic medical records following institutional ethics approval. Liver volumes were determined retrospectively from reviewing individual US images, and these, divided into tertiles, were analysed in the context of the predefined endpoints of (i) Primary - death or heart or liver transplantation, or (ii) Secondary - combined endpoint of death, transplantation, arrhythmia, or protein-losing enteropathy. RESULTS: Mean indexed liver volumes for the entire cohort (n = 199) were 1065.1 ± 312.1 ml/m2, range 387 to 2071 ml/m2. Patients with the largest liver volumes (highest tertile) were less likely to have a functioning fenestration compared to those in the lowest tertile 44% versus 56% p = 0.016 and experienced the highest burden of mortality and heart or heart-liver transplantation, p = 0.016, and were more likely to reach the composite endpoint of death, protein-losing enteropathy, arrhythmia, or transplantation, p = 0.010. Liver volumes had an overall predictive accuracy for the combined outcome of 61% (CI 53%, 67%, p = 0.009). CONCLUSIONS: Liver volumetry may serve as a potentially important congestion biomarker for adverse outcomes after the Fontan operation.

Postmortem magnetic resonance imaging findings of tricuspid atresia with ventricular and atrial septal defects and subvalvular pulmonic stenosis in a Japanese native Noma horse.

The necropsy of a 2-day-old Noma horse that died of weakness showed an enlarged cardiac base and a narrow cardiac apex, suggesting cardiac malformation. The excised heart underwent imaging to investigate its luminal structure. On three-dimensional magnetic resonance imaging, the right atrium and right ventricle were discontinuous. The right atrium communicated with the left atrium and the left ventricle communicated with the right ventricle. The lumen narrowed near the pulmonary artery valve. Since the same findings were observed on gross examination, the foal was diagnosed with tricuspid atresia with ventricular and atrial septal defects, along with subvalvular pulmonic stenosis.

Isoproterenol Challenge Unmasking Dynamic Bulbo-Ventricular Foramen Restriction.

Isoproterenol stress test during cardiac catheterization unmasked dynamic bulbo-ventricular foramen restriction in a 5-year-old boy with bidirectional Glenn anastomosis for tricuspid atresia/transposed great arteries and unexplained syncope.

Juxtaposition of the Atrial Appendages: A Large Echocardiographic Series.

Juxtaposition of the atrial appendages is known to occur in specific congenital heart lesions. Recognition of these variants is critical in balloon atrial septostomy and atrial switch operations. There remains little clinical data on the prevalence and associations of these lesions. This is the largest echocardiographic study of juxtaposition of the atrial appendages. This is a retrospective study using the Mt. Sinai echocardiogram database (EchoLAN), which contains echocardiogram reports performed or reviewed at Mt. Sinai Hospital (New York, NY) between 1992 and 2019. Each report was reviewed for associated intracardiac and extracardiac anomalies and the prevalence of juxtaposed atrial appendage among specific diagnosis, including tricuspid atresia, transposition of the great arteries, and double outlet right ventricle, was calculated. Descriptive and analytical statistics were performed as applicable, including Fisher's exact test, with p value < 0.05 considered statistically significant. Forty-nine patients had juxtaposed atrial appendages (1.2/1000 patients): Thirty-eight had LJRAA (0.9 per 1000 patients) and eleven had RJLAA (0.3 per 1000 patients). LJRAA was seen in 22% of tricuspid atresia, 6% of d-TGA, 1% of l-TGA, and 5% of DORV. RJLAA was seen in 2% of DORV, and none of the other lesions. Of associated lesions, dextrocardia, mesocardia, transposition, tricuspid atresia, double inlet left ventricle, and pulmonary valve stenosis were more likely to be present in LJRAA, while bicuspid aortic valve and left ventricular hypoplasia were more likely to be present in RJLAA. This study reaffirms our understanding of juxtaposition of the atrial appendages, its prevalence, and clinical importance.

Tricuspid atresia with absent pulmonary valve: A rare form of single ventricle.

Tricuspid atresia with an absent pulmonary valve is a rare congenital cardiac defect. Although extensive pathological reviews have been published in the past, there are only a handful of cases that have been successfully palliated to the stage of Fontan. We hereby describe the successful management of one such case and review the surgical strategies described in the literature.

Fontan operation for tricuspid atresia with absent pulmonary valve: a case series.

Combined tricuspid atresia and absent pulmonary valve with dysplasia of the right ventricular myocardium is a very rare congenital heart anomaly with a poor prognosis. We present three cases of this rare disease that reached the Fontan operation without prior surgical intervention of the right ventricle or pulmonary artery; no right ventriclar dilation was detected. All patients had uneventful post-operative courses.

An echocardiographic finding mimicking tricuspid atresia in a neonate with dilated cardiomyopathy.

We report a neonate with dilated cardiomyopathy and have echocardiographic findings consistent with "functional" tricuspid atresia. There was an echo-bright, plate-like tissue at the tricuspid valve position with no forward flow across it. This report underscores the role of right ventricle intracavitary haemodynamic influence on the tricuspid valve leaflet excursion and demonstrates a phenomenon of "pseudo or functional tricuspid atresia" mimicking tricuspid atresia in a patient with acute presentation of cardiomyopathy.

Monochorionic Twin Discordance for Horseshoe Lung and Tricuspid Atresia.

Background: The horseshoe lung is a congenital malformation in which the bases of the right and the left lung are fused. Case report: We describe a monochorionic twin gestation with malformation discordance. The abnormal twin had a horseshoe lung with hypoplasia of the right lung, tricuspid atresia, cleft lip, and a pelvic right kidney. Conclusion: The discordance of anomalies in this monochorionic twin suggests that a postzygotic mutation, epigenetic change, or environmental factors may be responsible for these malformations.

A unique arrangement of "kissing" atrial appendages.

We report a case of a 2-month-old boy with tricuspid and pulmonary atresia with a unique configuration of "kissing" atrial appendages. The case highlights the importance of computed tomography angiography in identifying such anomalies associated with complex congenital heart defects.

The pulmonary vascular bed in patients with functionally univentricular physiology and a Fontan circulation.

Fontan palliation represents one of the most remarkable surgical advances in the management of individuals born with functionally univentricular physiology. The operation secures adult survival for all but a few with unfavourable anatomy and/or physiology. Inherent to the physiology is passive transpulmonary blood flow, which produces a vulnerability to adequate filling of the systemic ventricle at rest and during exertion. Similarly, the upstream effects of passive flow in the lungs are venous congestion and venous hypertension, especially marked during physical activity. The pulmonary vascular bed has emerged as a defining character on the stage of Fontan circulatory behaviour and clinical outcomes. Its pharmacologic regulation and anatomic rehabilitation therefore seem important strategic therapeutic targets. This review seeks to delineate the important aspects of pulmonary artery development and maturation in functionally univentricular physiology patients, pulmonary artery biology, pulmonary vascular reserve with exercise, and pulmonary artery morphologic and pharmacologic rehabilitation.

Tricuspid atresia: Where are we now?

Tricuspid atresia (TA) is a complex congenital heart disease that presents with cyanosis in the neonatal period. It is invariably fatal if left untreated and requires multiple stages of palliation. Early recognition and timely surgical intervention are therefore pivotal in the management of these infants. This literature review considers the pathophysiology, presentation, investigations, and classification of TA. Moreover, it discusses the evidence upon which the latest medical and surgical treatments are based, as well as numerous recent case reports. Further work is needed to elucidate the etiology of TA, clarify the role of pharmacotherapy, and optimize the surgical management that these patients receive.

Tricuspid atresia with absent pulmonary valve and intact ventricular septum: successful bidirectional cavopulmonary anastomosis with complete exclusion of the right ventricle.

Tricuspid atresia with absent pulmonary valve and intact ventricular septum is an extremely rare cardiac malformation, historically associated with a poor prognosis. Only a few cases with successful surgical palliation have been reported in the literature. We present the case of an 8-month-old infant with this malformation who underwent successful bidirectional cavopulmonary anastomosis with complete exclusion of the right ventricle.

Learning from a case of right ventricular outflow tract stenting in tricuspid atresia with critical pulmonary stenosis.

Tricuspid valve atresia with severe pulmonary stenosis is one of the common cyanotic diseases in neonate. Child can succumb due to profound cyanosis and arterial hypoxaemia after closure of patent ductus arteriosus. Evolving procedure of right ventricular outflow tract stenting may be considered as a palliative procedure in such vulnerable group, destined for a later definitive management. The right ventricular outflow tract stenting is described essentially for tetralogy of Fallot physiology with a catheter course across tricuspid valve. We describe a case of successful right ventricular outflow tract stenting in a 5-day-old symptomatic neonate. We discuss the possible routes and the tips to facilitate right ventricular outflow tract stenting in such a case. This happens to be the first reported case description with successful stenting of neonate with tricuspid atresia with critical pulmonic stenosis.

Surgery of single ventricles in humanitarian practice: surgery for which patients?

OBJECTIVES: To analyse the feasibility and effectiveness in humanitarian practice of surgical management of children with single-ventricle heart condition. METHODS: Retrospective study of children with a single ventricle, managed by the association Mécénat-Chirurgie Cardiaque since 1996, with long-term follow-up after their return home. RESULTS: Of the 138 children in our cohort, 119 had one or more surgeries (180 procedures): palliative surgery alone (systemic-pulmonary anastomosis or banding), 41; partial cavo-pulmonary connection, 47; total cavo-pulmonary connection (mean age 8.5 years), 31. Operative mortality is 5.5%. After a mean follow-up of 5.6 years, 18 children (13%) were lost to follow-up. Survival at 10 years is 79% in children receiving surgery (palliative only, 72%; partial cavo-pulmonary connection, 77%; total cavo-pulmonary connection, 97%) versus 29% in children with no surgical intervention. The prognosis is better for tricuspid atresia and double-inlet left ventricle (86 and 83% survival at 10 years) than for double-outlet right ventricle or complete atrio-ventricular canal defect (64 and 68% at 5 years). CONCLUSION: The surgery of the single ventricle in humanitarian medicine allows a very satisfactory survival after one or more surgeries tending towards a total cavo-pulmonary connection as soon as possible.