Genetic heterogeneity and phenotypic anomalies in children with atrioventricular canal defect and tetralogy of Fallot

The particular anatomy of atrioventricular septal defect with a common valvar orifice in patients with Down syndrome: an echocardiographic study

OBJECTIVES

Atrioventricular septal defect with a common valvar orifice is associated with Down syndrome in almost half of cases. Clinical studies have shown that associated tetralogy of Fallot is more frequent in Down patients. The aim of this study was to compare the anatomy of the ventricles and of the ventricular component of the atrioventricular septal defect, looking for an outlet septum malalignment like in tetralogy of Fallot, in patients with and without Down syndrome.

METHODS

We reviewed retrospectively the echocardiographic examinations of all consecutive patients hospitalized with atrioventricular septal defect with a common orifice between 01/01/2016 and 01/09/2023. Anatomic and functional characteristics were compared between Down and non-Down patients.

RESULTS

A total of 310 patients were included (Down syndrome 210, 67.7 %). Outlet extension of the ventricular component of the defect with outlet septum anterior malalignment was found in 90.6 % of Down vs 12.8 % of non-Down patients (p < 0.001). Hypoplasia and apical filling of the right ventricle were more frequent in Down patients (p < 0.001). Associated tetralogy of Fallot was found in 16 Down vs 1 non-Down patients (p = 0.04). Atrioventricular septal malalignment was observed only in Down patients.

CONCLUSION

Outlet extension of the ventricular component of the defect is the rule in atrioventricular septal defect with a common orifice in Down patients, which could influence surgical repair. Hypoplastic right ventricle occurs only in Down patients. The presence of these characteristics in a fetus with atrioventricular septal defect with a common orifice should raise awareness of the high risk of associated Down syndrome.

A splicing variant in EFCAB7 hinders ciliary transport and disrupts cardiac development

The Tetralogy of Fallot (TOF), the most prevalent form of cyanotic congenital heart disease, stems from abnormal development of the outflow tract during embryogenesis. Despite the crucial role played by primary cilia in heart development, there is currently insufficient evidence to establish a causal relationship between defects in genes related to primary cilia and non-syndromic TOF. Here, we performed Sanger sequencing on 131 Chinese patients diagnosed with TOF and identified a splicing variant (c.683-1G > C) in the EFCAB7 gene. This splicing variant triggered exon skipping, leading to the production of a non-functional protein both in vitro and in vivo. Mice carrying this variant exhibited abnormal cardiac development, impaired ciliogenesis, disrupted Hedgehog signaling, and hindered Shh/Gli pathway activity. Through the integration of CUT&Tag data on Glis and bulk RNA-seq profiles of embryonic hearts at E10.5, we found that transcriptional downregulation of Gli target genes, including Myh6, Zfpm1, and Nkx2-5, is a consequence of Shh signaling inhibition. Our findings implicate EFCAB7 as a potential causative gene for TOF, underscoring the indispensable function of primary cilia in the intricate process of cardiac septation during heart development.

Human Genetics of Tetralogy of Fallot and Double-Outlet Right Ventricle

Tetralogy of Fallot (TOF) and double-outlet right ventricle (DORV) are conotruncal defects resulting from disturbances of the second heart field and the neural crest, which can occur as isolated malformations or as part of multiorgan syndromes. Their etiology is multifactorial and characterized by overlapping genetic causes. In this chapter, we present the different genetic alterations underlying the two diseases, which range from chromosomal abnormalities like aneuploidies and structural mutations to rare single nucleotide variations affecting distinct genes. For example, mutations in the cardiac transcription factors NKX2-5, GATA4, and HAND2 have been identified in isolated TOF cases, while mutations of TBX5 and 22q11 deletion, leading to haploinsufficiency of TBX1, cause Holt-Oram and DiGeorge syndrome, respectively. Moreover, genes involved in signaling pathways, laterality determination, and epigenetic mechanisms have also been found mutated in TOF and/or DORV patients. Finally, genome-wide association studies identified common single nucleotide polymorphisms associated with the risk for TOF.

The Burden of Congenital Heart Disease and Urogenital Lesions in a National Cohort of Hirschsprung Patients

BACKGROUND

Hirschsprung's disease (HSCR) is often associated with other congenital and chromosomal defects. This study aimed to describe the prevalence of congenital heart disease (CHD) and congenital urogenital lesions in children with HSCR, with and without Trisomy 21 and other associated anomalies, to guide appropriate screening.

METHODS

The Pediatric Health Information System was queried for patients with HSCR who underwent surgical treatment between 2016 and 2021. The prevalence of CHD, congenital urogenital lesions, Trisomy 21 and other congenital syndromes were calculated. Multivariable regression modeling was used to identify predictors of postoperative intensive care unit (ICU) admission and postoperative length of stay (LOS).

RESULTS

Of 2021 HSCR patients at 47 children's hospitals, 264 (13.1%) had CHD, 244 (12.1%) had Trisomy 21, and 103 (5.1%) had a congenital urogenital lesion. The prevalence of CHD (49.6 vs. 8.1%, P < 0.001) and of undergoing a cardiac intervention with associated CHD (40.5 vs. 23.1%, P = 0.002) were higher in patients with Trisomy 21 compared to those without. CHD was associated with an increased likelihood of postoperative ICU admission (OR: 1.6, 95% CI: 1.1, 2.2) and greater postoperative LOS (IRR: 2.6, 95% CI: 2.6, 2.7), irrespective of Trisomy 21 diagnosis.

CONCLUSIONS

The prevalence of CHD among HSCR patients (13.1%) was higher than previously reported, and CHD patients required more resource-intensive care after pull-through. While Trisomy 21 was associated with higher rates of CHD and cardiac intervention, 8.1% of HSCR patients without Trisomy 21 had CHD. Screening echocardiogram should be considered in all children diagnosed with HSCR, as CHD may influence perioperative risk stratification. However, screening renal ultrasound may have limited utility given the low prevalence of urogenital lesions in this population.

LEVEL OF EVIDENCE

Level III.

Genetics of atrioventricular canal defects

Atrioventricular canal defect (AVCD) represents a quite common congenital heart defect (CHD) accounting for 7.4% of all cardiac malformations. AVCD is a very heterogeneous malformation that can occur as a phenotypical cardiac aspect in the context of different genetic syndromes but also as an isolated, non-syndromic cardiac defect. AVCD has also been described in several pedigrees suggesting a pattern of familiar recurrence. Targeted Next Generation Sequencing (NGS) techniques are proved to be a powerful tool to establish the molecular heterogeneity of AVCD.

Given the complexity of cardiac embryology, it is not surprising that multiple genes deeply implicated in cardiogenesis have been described mutated in patients with AVCD. This review attempts to examine the recent advances in understanding the molecular basis of this complex CHD in the setting of genetic syndromes or in non-syndromic patients.

A single misstep in cardiac development explains the co-occurrence of tetralogy of fallot and complete atrioventricular septal defect in Down syndrome

Tetralogy of Fallot and a complete atrioventricular septal defect are thought to arise by distinct mechanisms, yet their co-occurrence is a recognized association. Analysis of the prevalence of co-occurrence in Down syndrome suggests a common developmental basis. Trisomy 21 may perturb cardiac progenitor cells before they enter the heart tube.

Types and distribution of congenital heart defects associated with trisomy 21 in Singapore

AIM

Atrioventricular septal defect (AVSD) is widely accepted as the most common type of congenital heart defect in trisomy 21. Most of these studies, however, were conducted in Caucasian communities. The few Asian studies that had been conducted on this subject yielded different results. In the largest study of its kind in Asia, we described the distribution of types of congenital heart defects associated with trisomy 21 in Singapore.

METHODS

Five hundred and eighty-eight patients with trisomy 21 born in 1996-2010, and confirmed by karyotyping, were included in the study. The diagnosis of congenital heart defects were made on echocardiography. Variables extracted for analysis were demographics (race and gender) and the types of congenital heart defects. Except for complex cyanotic heart defects, haemodynamically significant lesions were accounted for separately in cases where more than one type of congenital heart defect coexisted in a patient.

RESULTS

Ventricular septal defect (VSD) (39.2%) was the most common congenital heart defect associated with trisomy 21 in our study, followed by patent ductus arteriosus (34.3%), secundum atrial septal defect (23.4%) and AVSD (15.6%). This study validates previous smaller Asian studies identifying VSD as the most common cardiac lesion associated with trisomy 21. A high proportion (25.0%) of trisomy 21 patients with tetralogy of Fallot also had AVSDs. Coarctation of the aorta was uncommon.

CONCLUSION

VSD was the most common congenital heart defect seen in trisomy 21 in our study. A high proportion (25.0%) of trisomy 21 patients with tetralogy of Fallot also had AVSDs.

Maternal transmission of interstitial 8p23.1 deletion detected during prenatal diagnosis

We report on the first prenatally diagnosed interstitial 8p23.1 maternally inherited deletion. At 20 weeks of gestation (WG) the fetus was diagnosed with a complete atrioventricular canal. In infancy, the mother underwent a two-step cardiac surgery for an interrupted aortic arch type A associated to an inlet ventricular septal defect (VSD). A straddling of the tricuspid valve type B was confirmed during surgery. The outcome showed no cardiac failure or conduction anomalies. However, she presented with moderate intellectual disability. Classical and molecular cytogenetic studies on amniotic and maternal lymphocytes cells showed a nearly identical interstitial deletion of the 8p23.1 region encompassing the GATA4 gene locus (Mother: nt 6,913,337-12,580,828, fetus: nt 7,074,449-12,580,828) with no modification of the telomeric region. The relevance of our report is not only the maternal syndromic interstitial 8p23.1 deletion, but also maternal transmission which has never been reported before. The maternal and fetal phenotypes were not identical, however, even though they had the same cellular and molecular background: an alteration of the epithelial mesenchymal transition of the atrioventricular valvulo-septal complex where GATA4 plays a positive role in the regulation. We reviewed all cases of interstitial 8p23.1 deletions diagnosed either prenatally or postnatally.

Prenatal diagnosis of complete atrioventricular canal associated with tetralogy of Fallot

A complete atrioventricular canal defect occurs when an embryonic common atrioventricular valve fails to divide completely into 2 common atrioventricular valves. Tetralogy of Fallot is an abnormal embryologic development in which an unequal conotruncal division results in a small pulmonary artery and a large aortic artery. We report a case of prenatal diagnosis of a complete atrioventricular canal defect associated with tetralogy of Fallot.