Familial recurrence of congenital heart disease: an overview and review of the literature

Triple repeated fetal congenital heart disease linked to PLD1 mutation: a case report

BACKGROUND

Congenital heart disease occurs in approximately 1 in 100 cases. Although sibling occurrence is high (3-9%), the causative genes for this disease are still being elucidated. PLD1 (Phospholipase D1) is a recently discovered gene; however, few case reports have been published on it. In this report, we describe a case of triplicate fetal congenital heart disease that was diagnosed as a PDL1 mutation. Our objective is to explore the clinical manifestations of PLD1 mutations in this particular case.

CASE PRESENTATION

A 32-year-old Japanese woman (gravida, para 0) was introduced since fetus four chamber view was not clear and was diagnosed with ductus arteriosus-dependent left ventricular single ventricle and pulmonary atresia at 21 weeks and 1 day of gestation during her first pregnancy. Artificial abortion using Gemeprost was performed at 21 weeks and 5 days of gestation. The second pregnancy was diagnosed as pulmonary atresia with intact ventricular septum with cardiomegaly, a cardiothoracic area ratio of more than 35%, and a circulatory shunt at 13 weeks and 3 days of gestation. Subsequently, intrauterine fetal death was confirmed at 14 weeks and 3 days of gestation. Regarding the third pregnancy, fetal ultrasonography at 11 weeks and 5 days of gestation showed mild fetal hydrops and moderate tricuspid valve regurgitation. At 16 weeks and 5 days of gestation, the fetus was suspected to have a left ventricular-type single ventricle, trace right ventricle, pulmonary atresia with intact ventricular septum, or cardiomyopathy. Cardiac function gradually declined at 26 weeks of gestation, and intrauterine fetal death was confirmed at 27 weeks and 5 days of gestation. The fourth pregnancy resulted in a normal heart with good progression and no abnormal baby. We submitted the first and second fetuses' umbilical cord, third fetus' placenta, and the fourth fetus' blood to genetic testing using whole exome analysis with next generation sequencing. Genetic analysis identified hemizygous PLD1 mutations in the first, second, and third fetuses. The fourth fetus was heterozygous. In addition, the parents were heterozygous for PLD1. This case is based on three consecutive cases of homozygosity for the PLD1 gene in the sibling cases and the fetuses with recurrent right ventricular valve dysplasia. This will elucidate the cause of recurrent congenital heart disease and intrauterine fetal death and may serve as an indicator for screening the next fetus. To date, homozygous mutations in PLD1 that repeat three times in a row are not reported, only up to two times. The novelty of this report is that it was repeated three times, followed by a heterozygous live birth.

CONCLUSIONS

This report is consistent with previous reports that mutations in PLD1 cause right ventricular valve dysplasia. However, there have been few case reports of PLD1 mutations, and we hope that this report will contribute to elucidate the causes of congenital heart disease, especially right ventricular valve dysplasia, and that the accumulation of such information will provide more detailed information on PLD1 mutations in heart disease.

Systems analysis of de novo mutations in congenital heart diseases identified a protein network in the hypoplastic left heart syndrome

Despite a strong genetic component, only a few genes have been identified in congenital heart diseases (CHDs). We introduced systems analyses to uncover the hidden organization on biological networks of mutations in CHDs and leveraged network analysis to integrate the protein interactome, patient exomes, and single-cell transcriptomes of the developing heart. We identified a CHD network regulating heart development and observed that a sub-network also regulates fetal brain development, thereby providing mechanistic insights into the clinical comorbidities between CHDs and neurodevelopmental conditions. At a small scale, we experimentally verified uncharacterized cardiac functions of several proteins. At a global scale, our study revealed developmental dynamics of the network and observed its association with the hypoplastic left heart syndrome (HLHS), which was further supported by the dysregulation of the network in HLHS endothelial cells. Overall, our work identified previously uncharacterized CHD factors and provided a generalizable framework applicable to studying many other complex diseases. A record of this paper's Transparent Peer Review process is included in the supplemental information.

Recurrence pattern of non-syndromic familial congenital heart diseases among a large cohort of families from Egypt

Background

Congenital heart diseases (CHD) are the commonest congenital anomalies with increased risk in children born from families with affected members. However, various recurrence patterns of CHDs have been reported in different populations. Therefore, this work aimed to assess the recurrence patterns of CHDs in a large sample of Egyptian families.

Methods

From January 2020 to October 2021, non-syndromic children with confirmed CHDs were recruited. Data were collected from guardians of the recruited children and hospital records, including the index case’s cardiac diagnosis and CHD diagnosis of other affected family members with to determine their recurrence pattern, consanguinity, and multi-gestation status.

Results

A total of 130 recurrent cases with CHD were documented in 1960 families of children with CHD, including 66,989 members. Most recurrences were detected among first-degree relatives 50/130 (38.46%), especially siblings. Discordant recurrence was the most detected pattern (45.38%), followed by concordant recurrence (42.31%), and the least was group concordance. Recurrence rate was the highest for septal defects with left ventricular outflow tract obstruction (LVOTO) (11.8%) and anomalous venous drainage (11.1%), followed by septal defect with right ventricular outflow tract obstruction (RVOTO) (9.4%), isolated ventricular septal defect (VSD) category (8.2%) and LVOTO (8%). Familial recurrence was significant in consanguineous marriages [p = 0.0001; OR (95%CI) = 4.5 (2.25–9.01)] and in multi-gestations siblings: [p = 0.036; OR (95%CI) = 12.5(1.03–6.04)].

Conclusion

The recurrence of non-syndromic CHD is evident among first-degree relatives in Egyptian families, with mostly a discordant recurrence pattern. Recurrence was more notable in septal defects with LVOTO, anomalous venous drainage, septal defect with RVOTO, isolated VSD, and isolated LVOTO diagnostic categories. This finding will significantly impact family counseling, emphasizing higher recurrence in consanguineous parents.

Supplementary information

The online version contains supplementary material available at 10.1186/s12887-022-03640-4.

Exome Sequencing and Congenital Heart Disease in Sub-Saharan Africa

BACKGROUND

Congenital heart disease (CHD) is the most common birth defect and affects roughly 1% of the global population. There have been many large CHD sequencing projects in developing countries but none in sub-Saharan Africa. In this exome sequencing study, we recruited families from Lagos, Nigeria, affected by structural heart disease.

METHODS

Ninety-eight participants with CHD and an average age of 3.6 years were recruited from Lagos, Nigeria. Exome sequencing was performed on probands and parents when available. For genes of high interest, we conducted functional studies in Drosophila using a cardiac-specific RNA interference-based gene silencing system.

RESULTS

The 3 most common CHDs were tetralogy of Fallot (20%), isolated ventricular septal defect (14%), and transposition of the great arteries (8%). Ten percent of the cohort had pathogenic or likely pathogenic variants in genes known to cause CHD. In 64 complete trios, we found 34 de novo variants that were not present in the African population in the Genome Aggregation Database (v3). Nineteen loss of function variants were identified using the genome-wide distribution of selection effects for heterozygous protein-truncating variants (s_het). Nine genes caused a significant mortality when silenced in the Drosophila heart, including 4 novel disease genes not previously associated with CHD (UBB, EIF4G3, SREBF1, and METTL23).

CONCLUSIONS

This study identifies novel candidate genes and variants for CHD and facilitates comparisons with previous CHD sequencing studies in predominantly European cohorts. The study represents an important first step in genomic studies of CHD in understudied populations. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01952171.

High Familial Recurrence of Congenital Heart Defects in Laterality Defects Patients: An Evaluation of 184 Families

As a rare disease with genetic pathogenesis, observational study about familial CHD recurrence risk on CHD patients with laterality defects is lacking. This study aimed to investigate familial recurrence among families of patients with CHD and laterality defects, and compare them with CHD patients without laterality defects. A total of 184 patients with CHD and laterality defects treated in Cardiovascular Center, Children's Hospital of Fudan University were observed from 2008 to 2019. A detailed family history was documented by trained staff using questionnaires, and information about the subtypes of CHD and laterality defects was also collected. In addition, positive family history information, including all three degrees relatives and all affected family members, was reconfirmed by trained medical staff through face-to-face interviews, telephone interviews, and letter return visits. Of the 184 included patients, 30 had at least one family member (from among three linear generations and distant relatives) with CHD. The familial recurrence rate of CHD in our cohort was 16.3% (30/184), which was higher than the 3.3% (67/2024) of patients with CHD without laterality defects. This result shows that the recurrence rate among the first-, second-, and third-degree relatives was 11.7% (11/94), 1.5% (3/204), and 3.1% (6/91) and that the recurrence rate among siblings (21.4%, 9/42) was higher than that among parents (3.8%, 2/52). The familial recurrence risk of CHD among patients with CHD and laterality defects is high, which is consistent with the previous study that reported a high familial recurrence of heterotaxy of 10%. First-degree relatives have a higher recurrence rate than second- and third-degree relatives, especially siblings. These findings have important significance for prenatal screening, intervention, and genetic counseling in the Chinese population, but may not be generalizable to other populations that may have different rates of familial and sporadic cases.

Genetic Basis of Human Congenital Heart Disease

Congenital heart disease (CHD) is the most common major congenital anomaly with an incidence of ∼1% of live births and is a significant cause of birth defect-related mortality. The genetic mechanisms underlying the development of CHD are complex and remain incompletely understood. Known genetic causes include all classes of genetic variation including chromosomal aneuploidies, copy number variants, and rare and common single-nucleotide variants, which can be either de novo or inherited. Among patients with CHD, ∼8%-12% have a chromosomal abnormality or aneuploidy, between 3% and 25% have a copy number variation, and 3%-5% have a single-gene defect in an established CHD gene with higher likelihood of identifying a genetic cause in patients with nonisolated CHD. These genetic variants disrupt or alter genes that play an important role in normal cardiac development and in some cases have pleiotropic effects on other organs. This work reviews some of the most common genetic causes of CHD as well as what is currently known about the underlying mechanisms.

Genetics in congenital heart disease. Are we ready for it?

Genetics has rightly acquired an important place in almost all medical disciplines in recent years and this is certainly the case in the field of congenital cardiology. Not only has this led to greater insight into the pathophysiology of congenital heart defects but it also has a beneficial impact on patient management. Integration of clinical genetics in multidisciplinary centers of expertise for CHD is therefore a clear recommendation. Adult and pediatric cardiologists play a crucial role in the process of genetic evaluation of patients and families and should have be familiar with red flags for referral for further clinical genetic elaboration, counseling, and eventual testing. Some basic knowledge is also important for the correct interpretation of genetic testing results. In this review article, we provide a practical overview of what genetic evaluation entails, which type of genetic tests are possible today, and how this can be used in practice for the individual patient.

Genetic and genomics in congenital heart disease: a clinical review

OBJECTIVE

Discuss evidence referring to the genetic role in congenital heart diseases, whether chromosomic alterations or monogenic diseases.

DATA SOURCE

LILACS, PubMed, MEDLINE, SciELO, Google Scholar, and references of the articles found. Review articles, case reports, book chapters, master's theses, and doctoral dissertations were included.

SUMMARY OF FINDINGS

Congenital heart diseases are among the most common type of birth defects, afflicting up to 1% of the liveborn. Traditionally, the etiology was defined as a multifactorial model, with both genetic and external contribution, and the genetic role was less recognized. Recently, however, as the natural evolution and epidemiology of congenital heart diseases change, the identification of genetic factors has an expanding significance in the clinical and surgical management of syndromic or non-syndromic heart defects, providing tools for the understanding of heart development.

CONCLUSIONS

Concrete knowledge of congenital heart disease etiology and recognition of the genetic alterations may be helpful in the bedside management, defining prognosis and anticipating complications.

Genetic considerations for adults with congenital heart disease

Congenital heart disease (CHD) remains the most common birth defect, with an estimated incidence of approximately 1% of all births. The population of adults with CHD is growing rapidly with advances in medical care. Overall survival to adulthood in the current era estimated to exceed 90%. Genetic causes of CHD can be classified into several broad categories: (a) chromosomal aneuploidy, (b) large chromosomal deletion or duplication, (c) single gene mutation, and (d) copy number variation. However, only 20-30% of CHD cases have an established etiology characterized by either genetic abnormalities or environmental factors. The role of genetics in the field of adult CHD is only increasing. More adult patients with CHD are seeking genetic counseling to understand the etiology of their underlying CHD and the risks to future offspring. A multidisciplinary approach is essential to provide appropriate counseling to patients regarding indications for genetic testing and interpretations of results. Novel advances with precision medicine may soon enable clinicians to individualize therapies for a comprehensive approach to the care of adult patients with CHD.

Genetic Basis for Congenital Heart Disease: Revisited: A Scientific Statement From the American Heart Association

This review provides an updated summary of the state of our knowledge of the genetic contributions to the pathogenesis of congenital heart disease. Since 2007, when the initial American Heart Association scientific statement on the genetic basis of congenital heart disease was published, new genomic techniques have become widely available that have dramatically changed our understanding of the causes of congenital heart disease and, clinically, have allowed more accurate definition of the pathogeneses of congenital heart disease in patients of all ages and even prenatally. Information is presented on new molecular testing techniques and their application to congenital heart disease, both isolated and associated with other congenital anomalies or syndromes. Recent advances in the understanding of copy number variants, syndromes, RASopathies, and heterotaxy/ciliopathies are provided. Insights into new research with congenital heart disease models, including genetically manipulated animals such as mice, chicks, and zebrafish, as well as human induced pluripotent stem cell-based approaches are provided to allow an understanding of how future research breakthroughs for congenital heart disease are likely to happen. It is anticipated that this review will provide a large range of health care-related personnel, including pediatric cardiologists, pediatricians, adult cardiologists, thoracic surgeons, obstetricians, geneticists, genetic counselors, and other related clinicians, timely information on the genetic aspects of congenital heart disease. The objective is to provide a comprehensive basis for interdisciplinary care for those with congenital heart disease.

Risk factors for congenital heart defects in two populations residing in the same geographic area: a long-term population-based study, Southern Israel

BACKGROUND

Congenital Heart Defects (CHD) are the most common structural defects of newborns. Southern Israel's population is comprised of Jews (75%) and Arab-Bedouins (25%). The latter has a high rate of consanguinity and low abortion rate compared with the Jewish population, which led us to suspect a higher CHD prevalence in this population. Our aim was to compare maternal risk factors that are associated with CHD in these populations.

METHODS

All births during 1991-2011 in Soroka University Medical Center (n = 247, 289) with 6078 newborns having CHD were included. To account for same-woman deliveries, general estimating equation models adjusted for ethnicity, gender and birth number were used.

RESULTS

The total prevalence of CHD was 24.6/1000 live births, with 21.4 and 30 among Jewish and Bedouin populations, respectively, (p = 0.001). Multi-variant analysis of risk factors for CHD revealed that risk factors common to both populations included conception with fertility medications, sibling CHD, maternal CHD, diabetes mellitus, hypertension and anaemia. Risk factors that were specific for the Bedouin population were - maternal age over 35 years, recurrent pregnancy loss and in vitro fertilisation. However, sibling CHD was more common as a CHD risk factor in the Jewish compared with the Bedouin population (Adjusted OR 10.23 versus 3.19, respectively).

CONCLUSIONS

The prevalence of CHD is higher in both the Bedouin and Jewish populations than previously reported. Several maternal factors were associated with CHD specifically for a certain population. Risk factors for CHD vary in populations residing in the same geographic area.

Fetal cardiac abnormalities: Genetic etiologies to be considered

Congenital heart diseases are a common prenatal finding. The prenatal identification of an associated genetic syndrome or a major extracardiac anomaly helps to understand the etiopathogenic diagnosis. Besides, it also assesses the prognosis, management, and familial recurrence risk while strongly influences parental decision to choose termination of pregnancy or postnatal care. This review article describes the most common genetic diagnoses associated with a prenatal finding of a congenital heart disease and a suggested diagnostic process.

Recurrent Congenital Heart Diseases Among Neonates Born to Mothers with Congenital Heart Diseases

The frequency of newborns with congenital heart disease (CHD) is approximately 1% in the general population; however, the recurrence rate of CHD in mothers with CHD differs in ethnicity and reports. We therefore aimed to determine the prevalence of CHD among neonates born to mothers with CHD in our institute in Japan. We reviewed the medical charts of 803 neonates delivered by 529 women with CHD at the National Cerebral and Cardiovascular Center from 1982 to 2016. They included isolated ventricular septal defect (VSD,31.4%), isolated atrial septal defect (ASD, 23.3%), tetralogy of Fallot (TOF,10.6%). We defined CHD in neonates as being diagnosed within 1 month of birth. We estimated that the average rate of the CHD recurrence was 3.1%. The recurrence ratios in each maternal CHD were 8.6%, 7.1%, 6.2%, 4.8%, 3.6%, and 1.5% for PS, CoA, TOF, atrioventricular septal defect, VSD, and ASD, respectively. The rate of CHD in offsprings whose mothers have CHD was 3 times greater than that of mothers with healthy hearts. Almost half of neonates with CHD had the same phenotype as their mother in our series. Especially, PS and CoA were closely related to the type of maternal CHD.

The Combined Use of Ultrasound and Fetal Magnetic Resonance Imaging for a Comprehensive Fetal Neurological Assessment in Fetal Congenital Cardiac Defects: Scientific Impact Paper No. 60

Heart problems are common in newborn babies, affecting approximately 5-10 in 1000 babies. Some are more serious than others, but most babies born with heart problems do not have other health issues. Of those babies who have a serious heart problem, almost 1 in 4 will have heart surgery in their first year. In the UK, pregnant women are offered a scan at around 20 weeks to try and spot any heart problems. In most cases there is not a clear reason for the problem, but sometimes other issues, such as genetic conditions, are discovered. In recent years the care given to these babies after they are born has improved their chances of surviving. However, it is recognised that babies born with heart problems have a risk of delays in their learning and development. This may be due to their medical condition, or as a result of surgery and complications after birth. In babies with heart problems, there is a need for more research on ultrasound and magnetic resonance imaging (MRI) to understand how the brain develops and why these babies are more likely to have delays in learning and development. This paper discusses the way ultrasound and MRI are used in assessing the baby's brain. Ultrasound is often used to spot any problems, looking at how the baby's brain develops in pregnancy. Advances in ultrasound technologies have made this easier. MRI is well-established and safe in pregnancy, and if problems in the brain have been seen on ultrasound, MRI may be used to look at these problems in more detail. While it is not always clear what unusual MRI findings can mean for the baby in the long term, increased understanding may mean parents can be given more information about possible outcomes for the baby and may help to improve the counselling they are offered before their baby's birth.

Impact of Improved Survival in Congenital Heart Disease on Incidence of Disease

Survival rates and life expectancies for patients with congenital heart disease (CHD) have dramatically increased, and these patients are now reaching reproductive age. As they reproduce, questions pertaining to recurrent risk of disease and the impact on incidence rates have emerged. Recurrence rates for CHD have been estimated at 3% to 5%, although, due to the complex genetics underlying CHD, this range may represent an underestimation of the true risk. Debate still exists on whether the impact of recurrence of disease has been reflected in incidence rates. Although incidence rates have undoubtedly increased, the mechanism underlying this remains unclear; improved detection likely accounts for the majority of the observed increase; however, a true increase may be present simultaneously. Concurrently, certain factors, including improved fetal detection and elective terminations, infertility, increased rates of spontaneous abortion and intrauterine fetal demise in women with CHD, and folic acid supplementation, are leading to decreases in the incidence of CHD. It is likely that the full impact of improved survival and heritability of CHD on incidence rates remains to be seen and will likely be attenuated by other factors acting to decrease incidence.

Whole-exome sequencing identifies R1279X of MYH6 gene to be associated with congenital heart disease

BACKGROUND

Myosin VI, encoded by MYH6, is expressed dominantly in human cardiac atria and plays consequential roles in cardiac muscle contraction and comprising the cardiac muscle thick filament. It has been reported that the mutations in the MYH6 gene associated with sinus venosus atrial septal defect (ASD type III), hypertrophic (HCM) and dilated (DCM) cardiomyopathies.

METHODS

Two patients in an Iranian family have been identified who affected to Congenital Heart Disease (CHD). The male patient, besides CHD, shows that the thyroglossal sinus, refractive errors of the eye and mitral stenosis. The first symptoms emerged at the birth and diagnosis based on clinical features was made at about 5 years. The family had a history of ASD. For recognizing mutated gene (s), whole exome sequencing (WES) was performed for the male patient and variants were analyzed by autosomal dominant inheritance mode.

RESULTS

Eventually, by several filtering processes, a mutation in MYH6 gene (NM_002471.3), c.3835C > T; R1279X, was identified as the most likely disease-susceptibility variant and then confirmed by Sanger sequencing in the family. The mutation frequency was checked out in the local databases. This mutation results in the elimination of the 660 amino acids in the C-terminal of Myosin VI protein, including the vital parts of the coiled-coil structure of the tail domain.

CONCLUSIONS

Our study represents the first case of Sinus venosus defect caused directly by MYH6 stop codon mutation. Our data indicate that by increase haploinsufficiency of myosin VI, c.3835C > T mutation with reduced penetrance could be associated with CHD.

Some Isolated Cardiac Malformations Can Be Related to Laterality Defects

Human beings are characterized by a left–right asymmetric arrangement of their internal organs, and the heart is the first organ to break symmetry in the developing embryo. Aberrations in normal left–right axis determination during embryogenesis lead to a wide spectrum of abnormal internal laterality phenotypes, including situs inversus and heterotaxy. In more than 90% of instances, the latter condition is accompanied by complex and severe cardiovascular malformations. Atrioventricular canal defect and transposition of the great arteries—which are particularly frequent in the setting of heterotaxy—are commonly found in situs solitus with or without genetic syndromes. Here, we review current data on morphogenesis of the heart in human beings and animal models, familial recurrence, and upstream genetic pathways of left–right determination in order to highlight how some isolated congenital heart diseases, very common in heterotaxy, even in the setting of situs solitus, may actually be considered in the pathogenetic field of laterality defects.

Familial Aggregation and Heritability of Congenital Heart Defects

BACKGROUND

Congenital heart defects (CHD) are known to cluster within families, but existing evidence varies for the estimates of familial relative risk (RR). We aimed to examine familial aggregation and heritability of CHD in the general population of Taiwan.Methods and Results:We conducted a population-based family study using the Taiwan National Health Insurance (NHI) research database. Individuals with affected first-degree (n=295,636) or second-degree (n=73,985) relatives were identified from all NHI beneficiaries (n=23,422,955) registered in 2012. Diagnoses of CHD for all study subjects were ascertained between January 1, 1996 and December 31, 2012. Having a twin, a first-degree relative and an affected second-degree relative were associated with an adjusted RR of 12.03 (11.59-12.49), 4.91 (4.85-4.97) and 1.21 (1.14-1.28) for CHD, respectively. Individuals with 1 affected first-degree relative had a RR of 4.78 (4.72-4.84), and those with ≥2 had an RR of 7.10 (6.77-7.45) for CHD. The estimated accountability for phenotypic variance of CHD was 37.3% for familial transmission and 62.8% for non-shared environmental factors.

CONCLUSIONS

Our results indicated that CHD tend to cluster within families, and approximately one-third of phenotypic variance was explained by familial factors.

Advances in the Genetics of Congenital Heart Disease: A Clinician's Guide

Our understanding of the genetics of congenital heart disease (CHD) is rapidly expanding; however, many questions, particularly those relating to sporadic forms of disease, remain unanswered. Massively parallel sequencing technology has made significant contributions to the field, both from a diagnostic perspective for patients and, importantly, also from the perspective of disease mechanism. The importance of de novo variation in sporadic disease is a recent highlight, and the genetic link between heart and brain development has been established. Furthermore, evidence of an underlying burden of genetic variation contributing to sporadic and familial forms of CHD has been identified. Although we are still unable to identify the cause of CHD for most patients, recent findings have provided us with a much clearer understanding of the types of variants and their individual contributions and collectively mark an important milestone in our understanding of both familial and sporadic forms of disease.

Conditional Creation and Rescue of Nipbl-Deficiency in Mice Reveals Multiple Determinants of Risk for Congenital Heart Defects

Elucidating the causes of congenital heart defects is made difficult by the complex morphogenesis of the mammalian heart, which takes place early in development, involves contributions from multiple germ layers, and is controlled by many genes. Here, we use a conditional/invertible genetic strategy to identify the cell lineage(s) responsible for the development of heart defects in a Nipbl-deficient mouse model of Cornelia de Lange Syndrome, in which global yet subtle transcriptional dysregulation leads to development of atrial septal defects (ASDs) at high frequency. Using an approach that allows for recombinase-mediated creation or rescue of Nipbl deficiency in different lineages, we uncover complex interactions between the cardiac mesoderm, endoderm, and the rest of the embryo, whereby the risk conferred by genetic abnormality in any one lineage is modified, in a surprisingly non-additive way, by the status of others. We argue that these results are best understood in the context of a model in which the risk of heart defects is associated with the adequacy of early progenitor cell populations relative to the sizes of the structures they must eventually form.

Cilia gene mutations cause atrioventricular septal defects by multiple mechanisms

Atrioventricular septal defects (AVSDs) are a common severe form of congenital heart disease (CHD). In this study we identified deleterious non-synonymous mutations in two cilia genes, Dnah11 and Mks1, in independent N-ethyl-N-nitrosourea-induced mouse mutant lines with heritable recessive AVSDs by whole-exome sequencing. Cilia are required for left/right body axis determination and second heart field (SHF) Hedgehog (Hh) signaling, and we find that cilia mutations affect these requirements differentially. Dnah11^avc4 did not disrupt SHF Hh signaling and caused AVSDs only concurrently with heterotaxy, a left/right axis abnormality. In contrast, Mks1^avc6 disrupted SHF Hh signaling and caused AVSDs without heterotaxy. We performed unbiased whole-genome SHF transcriptional profiling and found that cilia motility genes were not expressed in the SHF whereas cilia structural and signaling genes were highly expressed. SHF cilia gene expression predicted the phenotypic concordance between AVSDs and heterotaxy in mice and humans with cilia gene mutations. A two-step model of cilia action accurately predicted the AVSD/heterotaxyu phenotypic expression pattern caused by cilia gene mutations. We speculate that cilia gene mutations contribute to both syndromic and non-syndromic AVSDs in humans and provide a model that predicts the phenotypic consequences of specific cilia gene mutations.

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.

Genetic testing in congenital heart disease: A clinical approach

Congenital heart disease (CHD) is the most common type of birth defect. Traditionally, a polygenic model defined by the interaction of multiple genes and environmental factors was hypothesized to account for different forms of CHD. It is now understood that the contribution of genetics to CHD extends beyond a single unified paradigm. For example, monogenic models and chromosomal abnormalities have been associated with various syndromic and non-syndromic forms of CHD. In such instances, genetic investigation and testing may potentially play an important role in clinical care. A family tree with a detailed phenotypic description serves as the initial screening tool to identify potentially inherited defects and to guide further genetic investigation. The selection of a genetic test is contingent upon the particular diagnostic hypothesis generated by clinical examination. Genetic investigation in CHD may carry the potential to improve prognosis by yielding valuable information with regards to personalized medical care, confidence in the clinical diagnosis, and/or targeted patient follow-up. Moreover, genetic assessment may serve as a tool to predict recurrence risk, define the pattern of inheritance within a family, and evaluate the need for further family screening. In some circumstances, prenatal or preimplantation genetic screening could identify fetuses or embryos at high risk for CHD. Although genetics may appear to constitute a highly specialized sector of cardiology, basic knowledge regarding inheritance patterns, recurrence risks, and available screening and diagnostic tools, including their strengths and limitations, could assist the treating physician in providing sound counsel.

Pedigree-based Analysis of Inherited and Noninherited Risk Factors of Congenital Heart Defects

BACKGROUND

Although congenital heart defect (CHD) pedigrees are rare, they are generally taken as evidence of the existence of a genetic etiologic mechanism or environmental factors common to family members, or a combination of both. Therefore, the analysis of CHD pedigrees is important for bridging the gap in our knowledge of its etiology.

AIMS

To assess the prevalence of CHD and evaluate the nongenetic factors in the CHD patients and healthy controls in the pedigrees.

STUDY DESIGN

Observational retrospective study.

SUBJECTS

Twenty-three CHD pedigrees were involved in the prevalence statistics; thirty-nine CHD cases and fifty-two healthy controls in the CHD pedigrees were included in the family-based noninherited factors analysis.

OUTCOME MEASURES

The three-degree relatives and overall CHD prevalence were calculated. Thirty-four noninherited risk factors were compared between the CHD and control groups, first by univariate analysis and later by multivariable logistic stepwise regression analysis.

RESULTS

The CHD prevalence of the probands' relatives in all pedigrees was 8.0%, and it was 10.9%, 2.9% and 11.9% in first-, second- and third-degree relatives, respectively. The three risk factors, including maternal febrile illnesses (OR=14.2, 95%CI: [1.5 - 133.7]), influenza (OR=6.9 [2.0 - 23.6]) and air pollution (OR=13.5 [2.6 - 70.5]), were strongly associated with a higher risk of CHD in our sample.

CONCLUSIONS

For the cluster and high prevalence of CHD in the collected pedigrees, our study confirms that genetic factors play a major role in the pathogenesis of CHD, while environmental factors, such as maternal febrile illnesses, influenza and air pollution, may also increase the burden of risk for CHD pathogenesis.

Genetics and genetic testing in congenital heart disease

Congenital heart defects (CHDs) are structural abnormalities of the heart and great vessels that are present from birth. The presence or absence of extracardiac anomalies has historically been used to identify patients with possible monogenic, chromosomal, or teratogenic CHD causes. These distinctions remain clinically relevant, but it is increasingly clear that nonsyndromic CHDs can also be genetic. This article discusses key morphologic, molecular, and signaling mechanisms relevant to heart development, summarizes overall progress in molecular genetic analyses of CHDs, and provides current recommendations for clinical application of genetic testing.

Functional zebrafish studies based on human genotyping point to netrin-1 as a link between aberrant cardiovascular development and thyroid dysgenesis

Congenital hypothyroidism caused by thyroid dysgenesis (CHTD) is a common congenital disorder with a birth prevalence of 1 case in 4000 live births, and up to 8% of individuals with CHTD have co-occurring congenital heart disease. Initially we found nine patients with cardiac and thyroid congenital disorders in our cohort of 158 CHTD patients. To enrich for a rare phenotype likely to be genetically simpler, we selected three patients with a ventricular septal defect for molecular studies. Then, to assess whether rare de novo copy number variants and coding mutations in candidate genes are a source of genetic susceptibility, we used a genome-wide single-nucleotide polymorphism array and Sanger sequencing to analyze blood DNA samples from selected patients with co-occurring CHTD a congenital heart disease. We found rare variants in all three patients, and we selected Netrin-1 as the biologically most plausible contributory factor for functional studies. In zebrafish, ntn1a and ntn1b were not expressed in thyroid tissue, but ntn1a was expressed in pharyngeal arch mesenchyme, and ntn1a-deficient embryos displayed defective aortic arch artery formation and abnormal thyroid morphogenesis. The functional activity of the thyroid in ntn1a-deficient larvae was, however, preserved. Phenotypic analysis of affected zebrafish indicates that abnormal thyroid morphogenesis resulted from a lack of proper guidance exerted by the dysplastic vasculature of ntn1a-deficient embryos. Hence, careful phenotyping of patients combined with molecular and functional studies in zebrafish identify Netrin-1 as a potential shared genetic factor for cardiac and thyroid congenital defects.

Preconceptual Folic Acid Use and Recurrence Risk Counseling for Congenital Heart Disease

OBJECTIVE

Recurrence risk of congenital heart disease (CHD) in families with an affected first-degree relative is increased as compared with the general population. Advances in genetic testing and evidence that preconceptual folic acid supplementation may decrease risk of CHD warrant preventative counseling for at-risk families. Our goal was to document patterns of preconceptual folic acid supplementation and recurrence risk counseling in at-risk families in order to identify opportunities for improved preventative care.

DESIGN

Mothers referred for a fetal echocardiogram were prospectively enrolled. Cases were defined as mothers deemed to be at higher risk of having an affected fetus with CHD given an affected parent or affected previous pregnancy with CHD. Controls were defined as mothers with no prenatal risk factors. Mothers completed a validated questionnaire assessing use of folic acid supplementation and receipt of recurrence risk counseling. Chi-square analyses were performed to analyze questionnaire responses and demographic data.

RESULTS

A total of 314 subjects participated (controls = 216, cases = 98). Cases took preconceptual folic acid supplementation more often than controls (P < .001), but only 55% started preconceptually. Maternal advanced education and counseling (P < .001) were associated with preconceptual supplementation, whereas complexity of CHD in the relative was not. While 70% of cases received some recurrence risk counseling, those with advanced education and complex CHD in the affected relative were more likely to receive counseling. Few at-risk cases interacted with genetic services (19%).

CONCLUSIONS

At-risk mothers with lower education are less likely to take preconceptual folic acid supplementation or receive recurrence risk counseling. Health care providers should proactively provide this information to all at-risk patients and develop collaborations with genetic services.

Diagnosis and treatment of fetal cardiac disease: a scientific statement from the American Heart Association

BACKGROUND

The goal of this statement is to review available literature and to put forth a scientific statement on the current practice of fetal cardiac medicine, including the diagnosis and management of fetal cardiovascular disease.

METHODS AND RESULTS

A writing group appointed by the American Heart Association reviewed the available literature pertaining to topics relevant to fetal cardiac medicine, including the diagnosis of congenital heart disease and arrhythmias, assessment of cardiac function and the cardiovascular system, and available treatment options. The American College of Cardiology/American Heart Association classification of recommendations and level of evidence for practice guidelines were applied to the current practice of fetal cardiac medicine. Recommendations relating to the specifics of fetal diagnosis, including the timing of referral for study, indications for referral, and experience suggested for performance and interpretation of studies, are presented. The components of a fetal echocardiogram are described in detail, including descriptions of the assessment of cardiac anatomy, cardiac function, and rhythm. Complementary modalities for fetal cardiac assessment are reviewed, including the use of advanced ultrasound techniques, fetal magnetic resonance imaging, and fetal magnetocardiography and electrocardiography for rhythm assessment. Models for parental counseling and a discussion of parental stress and depression assessments are reviewed. Available fetal therapies, including medical management for arrhythmias or heart failure and closed or open intervention for diseases affecting the cardiovascular system such as twin-twin transfusion syndrome, lung masses, and vascular tumors, are highlighted. Catheter-based intervention strategies to prevent the progression of disease in utero are also discussed. Recommendations for delivery planning strategies for fetuses with congenital heart disease including models based on classification of disease severity and delivery room treatment will be highlighted. Outcome assessment is reviewed to show the benefit of prenatal diagnosis and management as they affect outcome for babies with congenital heart disease.

CONCLUSIONS

Fetal cardiac medicine has evolved considerably over the past 2 decades, predominantly in response to advances in imaging technology and innovations in therapies. The diagnosis of cardiac disease in the fetus is mostly made with ultrasound; however, new technologies, including 3- and 4-dimensional echocardiography, magnetic resonance imaging, and fetal electrocardiography and magnetocardiography, are available. Medical and interventional treatments for select diseases and strategies for delivery room care enable stabilization of high-risk fetuses and contribute to improved outcomes. This statement highlights what is currently known and recommended on the basis of evidence and experience in the rapidly advancing and highly specialized field of fetal cardiac care.

Risk of congenital heart disease in relatives of probands with conotruncal cardiac defects: an evaluation of 1,620 families

Current recurrence risk counseling for conotruncal cardiac defects (CTD) is based on empiric estimates from multiple studies. We examined the risk of congenital heart disease (CHD) in relatives of probands with CTDs to assist in counseling practices in the current era. One thousand six-twenty probands with CTDs and no reported chromosomal or genetic abnormalities were recruited sequentially. A three-generation pedigree was obtained for each proband by a genetic counselor detailing the presence and type of CHD in each family member. Risks and 95% confidence intervals (CI) were calculated for sub-groups of relatives based on degree of relationship for all probands and by individual lesion of the proband. For pairs of affected relatives, concordance rates were calculated. Severity of CHD in the affected relative was assessed. The risk of CHD was higher in siblings (4.4%, 95% CI 3.4-5.4) than in parents (1.5%, 95% CI 1.1-1.9). Risk varied by the cardiac lesion of the proband with the highest risk in first-degree relatives of probands with tetralogy of Fallot and the lowest in D-transposition of the great arteries. 39% of affected parents and 69% of affected siblings had a concordant lesion (i.e., CTD). Most affected siblings of probands with severe CTDs had complex defects (58%), whereas very few affected parents had complex defects (20%). These data suggest that recurrence risk varies by lesion and relationship, with substantial concordance observed by cardiac lesion and complexity of disease, particularly among siblings. These findings contribute to risk counseling in the current era.

New molecular genetic tests in the diagnosis of heart disease

With the increasing use of next-generation sequencing applications, there has been an increase in identification of genetic causes of cardiac disease. This technology has also enabled the transition of these genes into the clinical setting and the rapid growth of large gene tests for the diagnosis of heart disorders. The ability to combine tests to include similar, but distinct, diseases has shown that many genes can be responsible for a wide variety of both syndromic and nonsyndromic disorders. This article discusses the current state of molecular genetic diagnosis for cardiac disorders, focusing on diseases with mendelian inheritance.

Prevalence, pattern and outcome of congenital heart disease in Bhabha Atomic Research Centre Hospital, Mumbai

OBJECTIVE

To assess the prevalence, pattern and outcome of congenital heart disease (CHD) among the babies born in Bhabha Atomic Research Centre (BARC) Hospital, Mumbai and to compare the pattern of CHD with the study done in the same hospital in year 1999.

METHODS

A prospective, longitudinal study was conducted from January 2006 through December 2011. Babies presenting with murmur were closely followed up till the diagnosis and further to assess the outcome. 2-D Echocardiography was used as a diagnostic tool.

RESULTS

The overall prevalence of CHD was 13.28 per 1,000 live births. Ventricular septal defect (VSD) was the commonest CHD (42.86 %) followed by Atrial septal defect (ASD) (25.71 %) giving the prevalence of 5.69 and 3.41 per 1,000 live births respectively. Tetrology of Fallot's (TOF) was the main cyanotic CHD (8.57 %) with the prevalence of 1.13 per 1,000 live births. VSD and TOF were prevalent in males. ASD was prevalent in females. Associated structural anomalies were detected in 22.86 % cases; Down's syndrome being the commonest.Spontaneous closure rate of 71.4 % in muscular VSD and 50 % in perimembranous VSD was observed. All small sized VSD's closed spontaneously and all large sized VSD's required surgical intervention. Spontaneous closure was observed in 44.44 % of ASD cases. Overall, device closure was required in 17.14 % and 25.71 % underwent open heart surgery.

CONCLUSIONS

The pattern of CHD has remained almost the same compared to the previous study. The outcome was excellent due to early diagnosis, regular follow up and timely intervention.

Is a shorter atrioventricular septal length an intermediate phenotype in the spectrum of nonsyndromic atrioventricular septal defects?

BACKGROUND

Atrioventricular septal defects (AVSDs) account for 7% of all congenital cardiovascular malformations. The atrioventricular septum (AVS) is the portion of the septal tissue that separates the right atrium from the left ventricle; deficiency of the AVS contributes to the AVSD phenotype. A study of case and control families was performed to identify whether an intermediate phenotype consisting of a shortened AVS existed in relatives of children with AVSDs.

METHODS

AVS length (AVSL) was measured on the echocardiograms of clinically unaffected parents and siblings from families that were identified through children with nonsyndromic AVSDs and in families with no histories of congenital heart disease.

RESULTS

No significant differences were seen between case and control family members in terms of gender, age, weight, and height. AVSLs were significantly shorter in case parents compared with control parents. Similar findings were noted within the sibling groups. There was significant evidence for two-component distributions in the case parent, case sibling, and control sibling groups after standardizing AVSL for age and body surface area. Heritability of AVSL standardized for age and body surface area was 0.82 and 0.71 in nonsyndromic case and control families, respectively.

CONCLUSIONS

Evidence for two-component distributions from the analysis of AVSL standardized for age and body surface area for case parents and case siblings suggests the presence of an intermediate phenotype for nonsyndromic AVSD. The high heritability in the control families suggests that there may be polygenic involvement in the determination of AVSL. Broadening the definition of AVSD to include those with shortened AVSL may increase the power of genetic association and mapping studies to identify susceptibility genes for AVSD.

Consanguinity and the risk of congenital heart disease

Consanguineous unions have been associated with an increased susceptibility to various forms of inherited disease. Although consanguinity is known to contribute to recessive diseases, the potential role of consanguinity in certain common birth defects is less clear, particularly since the disease pathophysiology may involve genetic and environmental/epigenetic factors. In this study, we ask whether consanguinity affects one of the most common birth defects, congenital heart disease, and identify areas for further research into these birth defects, since consanguinity may now impact health on a near-global basis. A systematic review of consanguinity in congenital heart disease was performed, focusing on non-syndromic disease, with the methodologies and results from studies of different ethnic populations compared. The risks for congenital heart disease have been assessed and summarized collectively and by individual lesion. The majority of studies support the view that consanguinity increases the prevalence of congenital heart disease, however, the study designs differed dramatically. Only a few (n = 3) population-based studies that controlled for potential sociodemographic confounding were identified, and data on individual cardiac lesions were limited by case numbers. Overall the results suggest that the risk for congenital heart disease is increased in consanguineous unions in the studied populations, principally at first-cousin level and closer, a factor that should be considered in empiric risk estimates in genetic counseling. However, for more precise risk estimates a better understanding of the underlying disease factors is needed.

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.

Recurrence of congenital heart disease in cases with familial risk screened prenatally by echocardiography

Objectives. To evaluate the recurrence of congenital heart disease (CHD) in pregnant women with familial risk who had been referred for fetal echocardiography. Material and Methods. 1634 pregnancies from 1483 women with familial history of CHD in one or more relatives were studied. Fetal cardiologic diagnosis was compared with postnatal findings at 6 months or at autopsy. Results. Total recurrence rate of CHD was 3.98%, 4.06% in single familial risk, 2.9% in double, and 5% in multiple risk. It was 3.5% in case of one previously affected child; 4.5% with 2 children; 5.2% with the mother alone affected and 7,5% with father alone affected and 3.5% with a single distant relative. Exact concordance of CHD was found in 21.5% and a partial concordance in 20% of cases. Conclusions. Our data show a higher recurrence rate of CHD than previously published data and high relative risk ratios compared to normal population.

The changing epidemiology of congenital heart disease

Congenital heart disease is the most common congenital disorder in newborns. Advances in cardiovascular medicine and surgery have enabled most patients to reach adulthood. Unfortunately, prolonged survival has been achieved at a cost, as many patients suffer late complications, of which heart failure and arrhythmias are the most prominent. Accordingly, these patients need frequent follow-up by physicians with specific knowledge in the field of congenital heart disease. However, planning of care for this population is difficult, because the number of patients currently living with congenital heart disease is difficult to measure. Birth prevalence estimates vary widely according to different studies, and survival rates have not been well recorded. Consequently, the prevalence of congenital heart disease is unclear, with estimates exceeding the number of patients currently seen in cardiology clinics. New developments continue to influence the size of the population of patients with congenital heart disease. Prenatal screening has led to increased rates of termination of pregnancy. Improved management of complications has changed the time and mode of death caused by congenital heart disease. Several genetic and environmental factors have been shown to be involved in the etiology of congenital heart disease, although this knowledge has not yet led to the implementation of preventative measures. In this Review, we give an overview of the etiology, birth prevalence, current prevalence, mortality, and complications of congenital heart disease.

Investigating 22q11.2 deletion and other chromosomal aberrations in fetuses with heart defects detected by prenatal echocardiography

Congenital heart disease (CHD) is the most common birth defect and the leading cause of mortality in the first year of life. In fetuses with a heart defect, chromosomal abnormalities are very frequent. Besides aneuploidy, 22q11.2 deletion is one of the most recognizable chromosomal abnormalities causing CHD. The frequency of this abnormality varies in nonselected populations. This study aimed to investigate the incidence of the 22q11.2 deletion and other chromosomal alterations in a Brazilian sample of fetuses with structural cardiac anomalies detected by fetal echocardiography. In a prospective study, 68 fetuses with a heart defect were evaluated. Prenatal detection of cardiac abnormalities led to identification of aneuploidy or structural chromosomal anomaly in 35.3% of these cases. None of the fetuses with apparently normal karyotypes had a 22q11.2 deletion. The heart defects most frequently associated with chromosomal abnormalities were atrioventricular septal defect (AVSD), ventricular septal defect (VSD), and tetralogy of Fallot. Autosomal trisomies 18 and 21 were the most common chromosomal abnormalities. The study results support the strong association of chromosome alterations and cardiac malformation, especially in AVSD and VSD, for which a chromosome investigation is indicated. In fetuses with an isolated conotruncal cardiopathy, fluorescence in situ hybridization (FISH) to investigate a 22q11.2 deletion is not indicated.

New mutations in ZFPM2/FOG2 gene in tetralogy of Fallot and double outlet right ventricle

Conotruncal defects (CTDs) represent 15-20% of all congenital heart defects. Mutations in a number of genes have been associated with CTD in humans and animal models. We investigated the occurrence and the prevalence of GATA4, NKX2.5, ZFPM2/FOG2, GDF1, and ISLET1 gene mutations in a large cohort of individuals with CTD, including tetralogy of Fallot with or without pulmonary atresia (TOF, 178 patients), double outlet right ventricle (DORV, 13 patients), and truncus arteriosus (11 patients). Denaturing high-performance liquid chromatography (DHPLC) analysis followed by bidirectional sequencing disclosed no putative pathogenic mutation in GATA4, ISLET1, and GDF1 genes. Two novel (Ile227Val, Met544Ile) and one previously reported (Glu30Gly) possibly pathogenic missense variants were identified in the ZFPM2/FOG2 gene in 3 sporadic patients of 202 (1.5%) with CTD, including 1 of 178 (0.6%) with TOF and 2 of 13 (15.4%) with DORV. Mutation analysis also detected one known missense change (Arg25Cys) in NKX2.5 gene in two (1.1%) sporadic patients with TOF. These sequence alterations were found to be absent in 500 population-matched controls. In conclusion, the present results (i) indicate and confirm that mutations in the GATA4, GDF1, and ISLET1 genes are not major determinants in the pathogenesis of TOF, (ii) provide supportive evidence of an association between ZFPM2/FOG2 gene and TOF/DORV, and (iii) provide additional examples of the possible contribution of the Arg25Cys change in the NKX2.5 to a small number of TOF cases.

Haploinsufficiency of TAB2 causes congenital heart defects in humans

Congenital heart defects (CHDs) are the most common major developmental anomalies and the most frequent cause for perinatal mortality, but their etiology remains often obscure. We identified a locus for CHDs on 6q24-q25. Genotype-phenotype correlations in 12 patients carrying a chromosomal deletion on 6q delineated a critical 850 kb region on 6q25.1 harboring five genes. Bioinformatics prioritization of candidate genes in this locus for a role in CHDs identified the TGF-beta-activated kinase 1/MAP3K7 binding protein 2 gene (TAB2) as the top-ranking candidate gene. A role for this candidate gene in cardiac development was further supported by its conserved expression in the developing human and zebrafish heart. Moreover, a critical, dosage-sensitive role during development was demonstrated by the cardiac defects observed upon titrated knockdown of tab2 expression in zebrafish embryos. To definitively confirm the role of this candidate gene in CHDs, we performed mutation analysis of TAB2 in 402 patients with a CHD, which revealed two evolutionarily conserved missense mutations. Finally, a balanced translocation was identified, cosegregating with familial CHD. Mapping of the breakpoints demonstrated that this translocation disrupts TAB2. Taken together, these data clearly demonstrate a role for TAB2 in human cardiac development.

Genome-wide identification of mouse congenital heart disease loci

Empirical evidence supporting a genetic basis for the etiology of congenital heart disease (CHD) is limited and few disease-causing mutations have been identified. To identify novel CHD genes, we performed a forward genetic screen to identify mutant mouse lines with heritable CHD. Lines with recessive N-ethyl-N-nitrsourea-induced CHD-causing mutations were identified using a three-generation backcross. A hierarchical screening protocol was used to test the hypothesis that the fetal-to-neonatal circulatory transition unmasks the specific structural heart defects observed in CHD. Mice with heart defects were efficiently ascertained by selecting for pups exhibiting perinatal lethality and characterizing their cardiac pathology. A marked increase of perinatal lethality was observed in the mutagen-treated cohort compared with an untreated backcross population. Cardiac pathology on perinatal lethals revealed cardiovascular defects in 79 pups from 47 of 321 mutagenized lines. All identified structural abnormalities were analogous to previously described forms of human CHD. Furthermore, the phenotypic recurrence and variance patterns across all lines were similar to human CHD prevalence and recurrence patterns. We mapped the locus responsible for heritable atrioventricular septal defects in six lines (avc1-6). Our screen demonstrated that 'sporadic' CHD may have major genetic component and established a practical, efficient approach for identifying CHD candidate genes.

Recurrence of discordant congenital heart defects in families

BACKGROUND

Variation within a single gene might produce different congenital heart defects (CHDs) within a family, which could explain the previously reported familial aggregation of discordant CHDs. We investigated whether certain groups of discordant CHDs are more common in families than others.

METHODS AND RESULTS

Using Danish national population and health registers, we identified CHDs among all singletons born in Denmark during 1977-2005 and their first-degree relatives. In a cohort of 1 711 641 persons, 16 777 had CHDs, which we classified into 14 phenotypes. We estimated relative risks of discordant CHDs by history of specific CHDs in first-degree relatives. The relative risk of any dissimilar CHD given the specified CHD in first-degree relatives was as follows: heterotaxia, 2.00 (95% CI, 0.96 to 4.17); conotruncal defects, 2.78 (95% CI, 2.12 to 3.66); atrioventricular septal defects, 2.25 (95% CI, 1.39 to 3.66); anomalous pulmonary venous return, 1.76 (95% CI, 0.66 to 4.64); left- and right-ventricular outflow tract obstruction, 2.55 (95% CI, 1.87 to 3.48) and 3.09 (95% CI, 2.03 to 4.71), respectively; isolated atrial septal defects, 2.76 (95% CI, 2.11 to 3.61); isolated ventricular septal defects, 2.27 (95% CI, 1.75 to 2.94); persistent ductus arteriosus, 1.92 (95% CI, 1.32 to 2.79); other specified CHDs, 3.29 (95% CI, 2.51 to 4.32); and unspecified CHDs, 2.30 (95% CI, 1.76 to 3.00). Relative risks for all pairwise combinations of discordant CHD phenotypes gave no indications that certain constellations of CHDs cluster more in families than others.

CONCLUSIONS

We documented strong familial aggregation of discordant CHD phenotypes. However, we observed no excess clustering of specific CHD phenotypes among the first-degree relatives.

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.