Occurrence of cardiac malformations in relatives of children with transposition of the great arteries

Common Genetic Variants Contribute to Risk of Transposition of the Great Arteries

RATIONALE

Dextro-transposition of the great arteries (D-TGA) is a severe congenital heart defect which affects approximately 1 in 4,000 live births. While there are several reports of D-TGA patients with rare variants in individual genes, the majority of D-TGA cases remain genetically elusive. Familial recurrence patterns and the observation that most cases with D-TGA are sporadic suggest a polygenic inheritance for the disorder, yet this remains unexplored.

OBJECTIVE

We sought to study the role of common single nucleotide polymorphisms (SNPs) in risk for D-TGA.

METHODS AND RESULTS

We conducted a genome-wide association study in an international set of 1,237 patients with D-TGA and identified a genome-wide significant susceptibility locus on chromosome 3p14.3, which was subsequently replicated in an independent case-control set (rs56219800, meta-analysis P=8.6x10-10, OR=0.69 per C allele). SNP-based heritability analysis showed that 25% of variance in susceptibility to D-TGA may be explained by common variants. A genome-wide polygenic risk score derived from the discovery set was significantly associated to D-TGA in the replication set (P=4x10-5). The genome-wide significant locus (3p14.3) co-localizes with a putative regulatory element that interacts with the promoter of WNT5A, which encodes the Wnt Family Member 5A protein known for its role in cardiac development in mice. We show that this element drives reporter gene activity in the developing heart of mice and zebrafish and is bound by the developmental transcription factor TBX20. We further demonstrate that TBX20 attenuates Wnt5a expression levels in the developing mouse heart.

CONCLUSIONS

This work provides support for a polygenic architecture in D-TGA and identifies a susceptibility locus on chromosome 3p14.3 near WNT5A. Genomic and functional data support a causal role of WNT5A at the locus.

How Suitable Are Registry Data for Recurrence Risk Calculations? Validation of Diagnoses on 1,593 Families With Congenital Heart Disease

Background:

Congenital heart disease (CHD) occurs in approximately 1% of all live births, and 3% to 8% of these have until now been considered familial cases, defined as the occurrence of two or more affected individuals in a family. The validity of CHD diagnoses in Danish administrative registry data has only been studied previously in highly selected patient populations. These studies identified high positive predictive values (PPVs) and recurrence risk ratios (RRRs—ratio between probabilities of CHD given family history of CHD and no family history). However, the RRR can be distorted if registry data are used indiscriminately. Here, we investigated the consequences of misclassifications for the RRR using validated diagnoses on Danish patients with familial CHD.

Methods:

Danish citizens are assigned a civil registration number (CPR number) at birth or immigration, which acts as a unique identifier in the Danish registries, thus enabling connection of information from several registries. Utilizing the CPR number, we identified Danish patients with familial CHD and reviewed each patient’s file. We compared diagnoses from the registries with those manually assigned, which enabled calculation of the PPVs of diagnoses in the Danish registries, and from this, we deduced the false discovery rate (FDR). To measure the consequences on the RRR, the FDR was applied to a simulated data set with true RRR values of 2 and 10.

Results:

We validated diagnoses of 2,442 patients from 1,593 families. Of these, 874 patients were misclassified corresponding to an FDR of 36%. Applying this FDR on the simulated data sets, we found that the RRR decreased from 2 and 10 to 1.4 and 5.1, respectively. Lastly, we estimated that 11% of all cases with CHD were familial.

Conclusion:

We found that approximately one of nine of all cases with CHD are familial, and we also found that 36% of individuals with CHD in administrative medical registries are misclassified, which distort the RRR in simulated scenarios.

D-transposition of the great arteries: the current era of the arterial switch operation

This paper aims to update clinicians on "hot topics" in the management of patients with D-loop transposition of the great arteries (D-TGA) in the current surgical era. The arterial switch operation (ASO) has replaced atrial switch procedures for D-TGA, and 90% of patients now reach adulthood. The Adult Congenital and Pediatric Cardiology Council of the American College of Cardiology assembled a team of experts to summarize current knowledge on genetics, pre-natal diagnosis, surgical timing, balloon atrial septostomy, prostaglandin E1 therapy, intraoperative techniques, imaging, coronary obstruction, arrhythmias, sudden death, neoaortic regurgitation and dilation, neurodevelopmental (ND) issues, and lifelong care of D-TGA patients. In simple D-TGA: 1) familial recurrence risk is low; 2) children diagnosed pre-natally have improved cognitive skills compared with those diagnosed post-natally; 3) echocardiography helps to identify risk factors; 4) routine use of BAS and prostaglandin E1 may not be indicated in all cases; 5) early ASO improves outcomes and reduces costs with a low mortality; 6) single or intramural coronary arteries remain risk factors; 7) post-ASO arrhythmias and cardiac dysfunction should raise suspicion of coronary insufficiency; 8) coronary insufficiency and arrhythmias are rare but are associated with sudden death; 9) early- and late-onset ND abnormalities are common; 10) aortic regurgitation and aortic root dilation are well tolerated; and 11) the aging ASO patient may benefit from "exercise-prescription" rather than restriction. Significant strides have been made in understanding risk factors for cardiac, ND, and other important clinical outcomes after ASO.

[Congenital heart defects of the septa, endocardial cushions and the conotruncus]

During embryological development the heart develops from a simple tube into a complex fully developed heart with four chambers. Hence all congenital heart defects develop before the ninth week of gestation. Currently a steadily increasing number of genetic mutations have been found to be responsible for congenital heart defects. Nevertheless, up to now it has been impossible to diagnose a heart defect just on the basis of molecular pathology. Despite the current excellent prenatal and postnatal ultrasound diagnostics, the post-mortem examination is still the gold standard for the diagnosis of complex heart malformations. However, this requires knowledge of the pathomorphology of the heart malformation in question. Therefore, characteristic and distinguishing features of septal defects including atrioventricular septal defects are presented, especially as the latter are part of complex heart defects, such as conotruncal heart malformations.

Familial recurrence of congenital heart diseases

Familial recurrence of congenital heart disease (CHD), in particular, d-transposition of great arteries (d-TGA) is rare. However, there have been several reports in the literature of sibling recurrence of total anomalous pulmonary venous return (TAPVR). This is the first case report in the literature, describing mother to offspring recurrence of d-TGA. We describe two cases of non-syndromic CHD with mother to offspring and sibling recurrence. The first case is an antenatally diagnosed d-TGA on fetal echocardiogram at 25 weeks of gestational age in the offspring of a 30-year-old mother with d-TGA. The second case is a sibling reoccurrence of TAPVR diagnosed antenatally at 30 weeks of gestational age, with supradiaphragmatic TAPVR on fetal echocardiogram in a mother, whose first child was diagnosed with infradiaphragmatic TAPVR in infancy.

Increased prevalence of cardiovascular defects among 56,709 California twin pairs

This study compared the prevalence of cardiovascular defects in twin and singleton births and explored the influences of zygosity (monozygotic and dizygotic) and maternal age (<35 and >or=35 years of age) on concordance. Data on twin and singleton infants with (n = 628 twin pairs and n = 14,078 singletons) and without (n = 53,974 twin pairs and n = 4,858,255 singletons) cardiovascular defects were obtained from the California Birth Defects Monitoring Program and the California vital statistics birth and fetal death records during the period 1983-2003. Prevalence ratios (PR) (prevalence of twin/singleton) and approximate 95% confidence intervals were calculated for 16 congenital cardiovascular categories. Poisson regression techniques using log-linear models were employed to assess whether the probability of concordance of defects within each cardiovascular category varied by zygosity or maternal age. An increased prevalence was observed in twins compared to singletons in all 16 cardiovascular categories. Seven of the cardiovascular categories had at least double the prevalence in twins compared to singletons. Like-sex twins, as a proxy of monozygosity, had an increased prevalence of cardiovascular defects compared to unlike sex twins. Probabilities of concordance for flow lesions were higher among monozygotic than dizygotic twins. Our study provides evidence that twinning is associated with more cardiovascular defects than singletons. Increased concordance for flow lesions in monozygotic twins was observed, an observation that is in agreement with findings from familial recurrence studies of cardiovascular defects.

Congenital heart disease and genetics

Improvements in the diagnosis and treatment of congenital heart disease have drastically reduced the morbidity and mortality associated with such defects. Knowledge regarding the genetic contributions to congenital heart disease is considered to be in its infancy; however, the field of cardiovascular genetics in humans is moving at a rapid pace. This article discusses what is currently known about the genetic contribution to congenital heart disease, including structural defects and congenital cardiac arrhythmias. Genetic and chromosomal syndromes that involve the heart are reviewed along with genetic testing.

An echocardiographic study of diagnostic accuracy, prediction of surgical approach, and outcome for fetuses diagnosed with discordant ventriculo-arterial connections

Our aims were to examine the diagnostic accuracy of prenatal diagnosis of concordant atrioventricular and discordant ventriculo-arterial connections, the accuracy of predictions made concerning the postnatal surgical approach, and a description of the different subtypes related to outcome. All fetuses were evaluated at a tertiary centre for fetal cardiology between January, 1994, and December, 2003. In this period, we identified congenitally malformed hearts in 1,835 fetuses, of whom 56 (3%) met the criterions of inclusion. Of the total, 30 (54%) had an intact ventricular septum, 9 (16%) had an associated ventricular septal defect, 7 (13%) had a ventricular septal defect and pulmonary stenosis, 1 (2%) had pulmonary stenosis and an intact ventricular septum, 8 (14%) had a ventricular septal defect and aortic coarctation, and 1 (2%) had coarctation of the aorta with an intact ventricular septum. All the discordant ventriculo-arterial connections were correctly identified. For associated ventricular septal defects, the diagnostic sensitivity was 96%, with specificity of 88%, positive predictive value of 85%, and negative predictive value of 97%. For aortic coarctation, the sensitivity was 100%, specificity 96%, positive predictive value 82%, and negative predictive value 100%. The prediction of the surgical approach was accurate in 41 of 48 cases (85%). For those fetuses with pulmonary stenosis and ventricular septal defect, the ratio of the diameters of the pulmonary trunk was shown to be helpful in predicting the possibility of an arterial switch as opposed to the Rastelli type of repair. Of the 49 liveborn infants, 46 were alive at 30 days (94%, with 95% confidence intervals from 83 to 99%), and 43 at one year (88%, 95% confidence intervals from 75 to 95%). Deaths were mainly related to the anatomy of the coronary arteries, and associated cardiac lesions.

Elucidation of penetrance variability of aZIC3mutation in a family with complex heart defects and functional analysis ofZIC3mutations in the first zinc finger domain

We studied a series of 42 cases of transposition of the great arteries (TGA), a complex heart defect (CHD) that is two times more prevalent in males than in females. A mutation in the X chromosome at the ZIC3 gene was found in two affected siblings (one male, one female) and their unaffected mother. A second factor, skewed X-inactivation pattern explained the discrepancy between the daughter/mother phenotype. In this family, the missense mutation (p.W255G) was found in the first zinc finger of ZIC3, a domain that is relatively specific to each of the five human ZIC genes. It was tested further along with two other mutations of this domain (p.C253S and p.H286R). In transfected 3T3 cells, mutants p.W255G and p.H286R expressed lower protein levels, and an increased protein degradation (p.W255G only). Moreover, mutants p.C253S and p.W255G had a decreased transcription activation of the TK-luciferase reporter gene. Nuclear translocation of the three ZIC3 mutants varied considerably depending on the experimental models. Finally, p.W255G and p.H286R showed diminished activities for both left-right axis disturbance and neural crest induction in Xenopus embryos. These results suggest that mutations in the first zinc finger of ZIC3 mildly affect several functions of the protein.

Familial recurrence of heart defects in subjects with congenitally corrected transposition of the great arteries

Familial recurrence of congenitally corrected transposition of the great arteries (CCTGA) is considered uncommon. Most of the previous familial studies involved a small number of patients and referred to all situs and looping anomalies including single ventricle, heterotaxia, and other cardiac defects different from CCTGA. We performed a large, consecutive clinical case series study in order to detect the recurrence of congenital heart defects in families of children with the classic form of CCTGA. From January 1997 through December 2004, 102 consecutive patients with CCTGA were evaluated in four institutions. There were 59 male (57.8%) and 43 female (42.2%). Mean age was 8.6 +/- 7.8 years. Eighty-eight patients (86.3%) had situs solitus of the atria, 14 (13.7%) situs inversus. The cardiac and extracardiac anomalies among relatives and the patterns of familial recurrence were investigated. Relatives with congenital heart defects were found in 16/102 families (15.7%). Transposition of the great arteries (TGA) was the most common recurrent defect (6/102 families). Consanguinity was identified in the parents of three probands. Six probands had an unaffected twin-sib. Recurrence risks for congenital heart defects were calculated at 5.2% (6/116) for siblings. In conclusion, CCTGA is not always sporadic in families. The pattern of inheritance, the presence of consanguinity among parents and the recurrence of situs inversus could suggest, in some families, an autosomal recessive mechanism with similarities with that occurring in some pedigrees with heterotaxia. The recurrence of TGA and CCTGA in the same family suggests a pathogenetic link between these two anatomically different malformations.

CFC1 mutations in patients with transposition of the great arteries and double-outlet right ventricle

Recent investigations identified heterozygous CFC1 mutations in subjects with heterotaxy syndrome, all of whom had congenital cardiac malformations, including malposition of the great arteries. We hypothesized that a subset of patients with similar types of congenital heart disease---namely, transposition of the great arteries and double-outlet right ventricle, in the absence of laterality defects---would also have CFC1 mutations. Our analysis of the CFC1 gene in patients with these cardiac disorders identified two disease-related mutations in 86 patients. The present study identifies the first autosomal single-gene defect for these cardiac malformations and indicates that some cases of transposition of the great arteries and double-outlet right ventricle can share a common genetic etiology with heterotaxy syndrome. In addition, these results demonstrate that the molecular pathway involving CFC1 plays a critical role in normal and abnormal cardiovascular development.

Complete transposition of the great arteries: patterns of congenital heart disease in familial precurrence

BACKGROUND

Transposition of the great arteries (TGA) is considered to be associated only rarely with genetic syndromes and to have a low risk of precurrence among relatives of affected patients. Because most family studies have involved a relatively small number of patients and evaluated all types of TGA as a single group, we performed a large, prospective study investigating the precurrence of congenital heart disease in families of children with complete, nonsyndromic TGA.

METHODS AND RESULTS

From January 1997 through December 2000, 370 patients with nonsyndromic, complete TGA were consecutively evaluated and enrolled in the study. The occurrence of cardiac and noncardiac anomalies among relatives of the probands was investigated. Relatives with congenital heart disease were found in 37 of 370 families (10%), including 5 of 37 families (13.5%) with more than one affected relative. TGA itself was the most common precurrent malformation: complete TGA occurred in 6 families and congenitally corrected TGA occurred in 5 families. Precurrence risks for congenital heart disease were calculated at 1.8% (8 of 436) for siblings, 0.5% (4 of 740) for parents, 0.5% (16 of 3261) for first cousins, 0.2% (4 of 2101) for uncles/aunts, and 0.06% (1 of 1480) for grandparents.

CONCLUSIONS

The present study shows that TGA is not always sporadic in families. Precurrence of concordant cardiac defects within affected family members supports monogenic or oligogenic inheritance of TGA in certain kindreds. Moreover, the occurrence of complete TGA and congenitally corrected TGA among first-degree relatives in several different families strongly suggests an underlying pathogenetic link between these 2 malformations that has been previously unrecognized.