Echocardiographic evaluation of asymptomatic parental and sibling cardiovascular anomalies associated with congenital left ventricular outflow tract lesions

Cardiac problems in the fetus: a review for pediatric providers

PURPOSE OF REVIEW

The aim of this study was to provide pediatric providers with a review of the diagnosis and management of fetal cardiac disease in the current era.

RECENT FINDINGS

Prenatal detection of congenital heart disease (CHD) has improved but is still imperfect. In experienced hands, fetal echocardiography can detect severe CHD as early as the first trimester and a majority of more subtle conditions in the second and third trimesters. Beyond detection, a prenatal diagnosis allows for lesion-specific counseling for families as well as for development of a multidisciplinary perinatal management plan, which may involve in-utero treatment. Given the diversity of cardiac diagnoses and the rarity of some, collaborative multicenter fetal cardiac research has gained momentum in recent years.

SUMMARY

Accurate diagnosis of fetal cardiac disease allows for appropriate counseling, pregnancy and delivery planning, and optimization of immediate neonatal care. There is potential for improving fetal CHD detection rates. Fetal interventions are available for certain conditions, and fetal and pediatric cardiac centers have developed management plans specific to the expected postnatal physiology.

Association of Maternal Betaine-Homocysteine Methyltransferase (BHMT) and BHMT2 Genes Polymorphisms with Congenital Heart Disease in Offspring

To systematically explore the association of single nucleotide polymorphisms (SNPs) of maternal BHMT and BHMT2 genes with the risk of congenital heart disease (CHD) and its three subtypes including atrial septal defect (ASD), ventricular septal defect (VSD), and patent ductus arteriosus (PDA) in offspring. A hospital-based case-control study involving 683 mothers of CHD children and 740 controls was performed. Necessary exposure information was captured through epidemiological investigation. Totally twelve SNPs of maternal BHMT and BHMT2 genes were detected and analyzed systematically. The study showed that maternal BHMT gene polymorphisms at rs1316753 (CG vs. CC: OR = 1.96 [95% CI 1.41-2.71]; GG vs. CC: OR = 1.99 [95% CI 1.32-3.00]; dominant model: OR = 1.97 [95% CI 1.44-2.68]) and rs1915706 (TC vs. TT: OR = 1.93 [95% CI 1.44-2.59]; CC vs. TT: OR = 2.55 [95% CI 1.38-4.72]; additive model: OR = 1.77 [95% CI 1.40-2.24]) were significantly associated with increased risk of total CHD in offspring. And two haplotypes were observed to be significantly associated with risk of total CHD, including C-C haplotype involving rs1915706 and rs3829809 in BHMT gene (OR = 1.30 [95% CI 1.07-1.58]) and C-A-A-C haplotype involving rs642431, rs592052, rs626105, and rs682985 in BHMT2 gene (OR = 0.71 [95% CI 0.58-0.88]). Besides, a three-locus model involving rs1316753 (BHMT), rs1915706 (BHMT), and rs642431 (BHMT2) was identified through gene-gene interaction analyses (P < 0.01). As for three subtypes including ASD, VSD, and PDA, significant SNPs and haplotypes were also identified. The results indicated that maternal BHMT gene polymorphisms at rs1316753 and rs1915706 are significantly associated with increased risk of total CHD and its three subtypes in offspring. Besides, significant interactions between different SNPs do exist on risk of CHD. Nevertheless, studies with larger sample size in different ethnic populations and involving more SNPs in more genes are expected to further define the genetic contribution underlying CHD and its subtypes.

Considering the Genetic Architecture of Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is among the most severe cardiovascular malformations and understanding its causes is crucial to making progress in prevention and treatment. Genetic analysis is a broadly useful tool for dissecting complex causal mechanisms and it is playing a significant role in HLHS research. However, unlike classical Mendelian disorders where a relatively small number of genes are largely determinative of the occurrence and severity of the disease, the picture in HLHS is complex. De novo single-gene and copy number variant (CNV) disorders make an important contribution, but there is emerging evidence for causal contributions from lower penetrance and common variation. Integrating this emerging knowledge into clinical diagnostics and translating the findings into effective prevention and treatment remain challenges for the future.

Clinical implications of the biomechanics of bicuspid aortic valve and bicuspid aortopathy

Bicuspid aortic valve (BAV), which affects up to 2% of the general population, results from the abnormal fusion of the cusps of the aortic valve. Patients with BAV are at a higher risk for developing aortic dilatation, a condition known as bicuspid aortopathy, which is associated with potentially life-threatening sequelae such as aortic dissection and aortic rupture. Although BAV biomechanics have been shown to contribute to aortopathy, their precise impact is yet to be delineated. Herein, we present the latest literature related to BAV biomechanics. We present the most recent definitions and classifications for BAV. We also summarize the current evidence pertaining to the mechanisms that drive bicuspid aortopathy. We highlight how aberrant flow patterns can contribute to the development of aortic dilatation. Finally, we discuss the role cardiac magnetic resonance imaging can have in assessing and managing patient with BAV and bicuspid aortopathy.

Exome sequencing in multiplex families with left-sided cardiac defects has high yield for disease gene discovery

Congenital heart disease (CHD) is a common group of birth defects with a strong genetic contribution to their etiology, but historically the diagnostic yield from exome studies of isolated CHD has been low. Pleiotropy, variable expressivity, and the difficulty of accurately phenotyping newborns contribute to this problem. We hypothesized that performing exome sequencing on selected individuals in families with multiple members affected by left-sided CHD, then filtering variants by population frequency, in silico predictive algorithms, and phenotypic annotations from publicly available databases would increase this yield and generate a list of candidate disease-causing variants that would show a high validation rate. In eight of the nineteen families in our study (42%), we established a well-known gene/phenotype link for a candidate variant or performed confirmation of a candidate variant’s effect on protein function, including variants in genes not previously described or firmly established as disease genes in the body of CHD literature: BMP10, CASZ1, ROCK1 and SMYD1. Two plausible variants in different genes were found to segregate in the same family in two instances suggesting oligogenic inheritance. These results highlight the need for functional validation and demonstrate that in the era of next-generation sequencing, multiplex families with isolated CHD can still bring high yield to the discovery of novel disease genes.

Congenital heart disease is a common group of birth defects that are a leading cause of death in children under one year of age. There is strong evidence that genetics plays a role in causing congenital heart disease. While studies using individual cases have identified causative genes for those with a heart defect when accompanied by other birth defects or intellectual disabilities, for individuals who have only a heart defect without other problems, a genetic cause can be found in fewer than 10%. In this study, we enrolled families where there was more than one individual with a heart defect. This allowed us to take advantage of inheritance by searching for potential disease-causing genetic variants in common among all affected individuals in the family. Among 19 families studied, we were able to find a plausible disease-causing variant in eight of them and identified new genes that may cause or contribute to the presence of a heart defect. Two families had potential disease-causing variants in two different genes. We designed assays to test if the variants led to altered function of the protein coded by the gene, demonstrating a functional consequence that support the gene and variant as contributing to the heart defect. These findings show that studying families may be more effective than using individuals to find causes of heart defects. In addition, this family-based method suggests that changes in more than one gene may be required for a heart defect to occur.

Point on the Aortic Bicuspid Valve

Background—Bicuspid aortic valve (BAV) disease is the most prevalent congenital heart disease in the world. Knowledge about its subtypes origin, development, and evolution is poor despite the frequency and the potential gravity of this condition. Its prognosis mostly depends on the risk of aortic aneurysm development with an increased risk of aortic dissection. Aims—This review aims to describe this complex pathology in way to improve the bicuspid patients’ management. Study design—We reviewed the literature with MEDLINE and EMBASE databases using MeSH terms such as “bicuspid aortic valve”, “ascending aorta”, and “bicuspid classification”. Results—There are various classifications. They depend on the criteria chosen by the authors to differentiate subtypes. Those criteria can be the number and position of the raphes, the cusps, the commissures, or their arrangements regarding coronary ostia. Sievers’ classification is the reference. The phenotypic description of embryology revealed that all subtypes of BAV are the results of different embryological pathogenesis, and therefore, should be considered as distinct conditions. Their common development towards aortic dilatation is explained by the aortic media’s pathological histology with cystic medial necrosis. At the opposite, BAV seems to display a profound genetic heterogeneity with both sporadic and familial forms. BAV can be even isolated or combined with other congenital malformations. Conclusions—All those characteristics make this pathology a highly complex condition that needs further genetic, embryological, and hemodynamic explorations to complete its well described anatomy.

Retrospective comparison of parent-reported genetics knowledge, empowerment, and familial uptake of cardiac screening between parents who received genetic counseling by a certified genetic counselor and those who did not: A single US academic medical center study

Bicuspid aortic valve (BAV) is the most common congenital heart defect, which can cause severe cardiac complications. BAVs cluster in families and demonstrate high heritability. Cardiac screening for first-degree relatives of individuals with a BAV is recommended. This retrospective two-group study evaluated the impact of cardiovascular genetic counseling provided by a board-certified genetic counselor on parent-reported outcomes by comparing parental responses of those who received genetic counseling by a genetic counselor (GC group) for family history of BAV to those who did not (non-GC group). A retrospective chart review from May 2016 to June 2019 identified 133 pediatric patients with an isolated BAV. Parents of eligible probands were invited to complete an online survey assessing genetics knowledge, empowerment (Genomics Outcome Scale), and familial uptake of cardiac screening. Surveys were completed by 38/97 (39%) parents in the non-GC group and 20/36 (56%) parents in the GC group. The median genetics knowledge score was not significantly different between the two groups (GC group: 8, range 3-11 out of a maximum possible of 12; non-GC group: 7, range 2-11; p = .08). The mean empowerment score was not significantly different between the two groups (GC group: mean 24.6, SD 2.2; non-GC group: mean 23.2, SD 3.5; p = .06). The uptake of cardiac screening was significantly higher in the GC group with 39/59 (66%) total first-degree relatives reported as having been screened compared with 36/91 (40%) in the non-GC group (p = .002). Parent-reported outcomes in our study suggest that receiving genetic counseling by a board-certified genetic counselor significantly increased familial uptake of cardiac screening for first-degree relatives of pediatric patients with a BAV. Studies with larger sample sizes are needed to confirm the findings of this study; however, a referral to a genetic counselor should be considered for patients with a BAV.

Pregnancy related changes in Doppler gradients and left ventricular mechanics in women with sub-valvular or valvular aortic stenosis

BACKGROUND

The aim of our study was to characterize echocardiographic changes during pregnancy in women with known LVOT obstruction or AS compared to the healthy pregnancy controls, and to assess the relationship with pregnancy outcomes.

METHODS

We retrospectively studied 34 pregnant patients with congenital LVOT obstruction or AS with healthy age-matched pregnant controls. Patients with other significant valvular lesions, structural heart disease (LVEF < 40%), or prior valve surgery were excluded. All LVOTO/AS patients underwent a minimum of two consecutive echocardiograms between 1 year pre-conception and 1 year postpartum, with at least two studies during the pregnancy. Comprehensive echocardiographic evaluation was performed including speckle-tracking LV global longitudinal strain.

RESULTS

A total of 83 echocardiograms from the study group and 34 echocardiograms from the control group were evaluated. Over the range of LVOTO/AS, a significantly greater increase in the AV gradients and LV and LA volumes were observed as compared with the controls. In the sub-group of LVOTO/AS pregnant women with ≥ moderate (n = 8) versus < moderate LVOTO/AS (n = 26), averaged 2^nd /3^rd trimester LVEF was lower (51 ± 12)% versus (58 ± 4)%, (p = 0.02) and GLS was lower (-19.5 ± 2.8) versus (21.2 ± 2.4), (p = 0.06). Pregnancy was well tolerated despite these changes.

CONCLUSION

Among pregnant women with even milder forms of LVOTO/AS, increases in cardiac volumes and AV gradients can be expected over the course of pregnancy. Significant decreases in LV function and mechanics were only observed in women with moderate or greater LVOTO/AS, although still remained in normal range.

Common deletion variants causing protocadherin-α deficiency contribute to the complex genetics of BAV and left-sided congenital heart disease

Bicuspid aortic valve (BAV) with ~1%-2% prevalence is the most common congenital heart defect (CHD). It frequently results in valve disease and aorta dilation and is a major cause of adult cardiac surgery. BAV is genetically linked to rare left-heart obstructions (left ventricular outflow tract obstructions [LVOTOs]), including hypoplastic left heart syndrome (HLHS) and coarctation of the aorta (CoA). Mouse and human studies indicate LVOTO is genetically heterogeneous with a complex genetic etiology. Homozygous mutation in the Pcdha protocadherin gene cluster in mice can cause BAV, and also HLHS and other LVOTO phenotypes when accompanied by a second mutation. Here we show two common deletion copy number variants (delCNVs) within the PCDHA gene cluster are associated with LVOTO. Analysis of 1,218 white individuals with LVOTO versus 463 disease-free local control individuals yielded odds ratios (ORs) at 1.47 (95% confidence interval [CI], 1.13-1.92; p = 4.2 × 10-3) for LVOTO, 1.47 (95% CI, 1.10-1.97; p = 0.01) for BAV, 6.13 (95% CI, 2.75-13.7; p = 9.7 × 10-6) for CoA, and 1.49 (95% CI, 1.07-2.08; p = 0.019) for HLHS. Increased OR was observed for all LVOTO phenotypes in homozygous or compound heterozygous PCDHA delCNV genotype comparison versus wild type. Analysis of an independent white cohort (381 affected individuals, 1,352 control individuals) replicated the PCDHA delCNV association with LVOTO. Generalizability of these findings is suggested by similar observations in Black and Chinese individuals with LVOTO. Analysis of Pcdha mutant mice showed reduced PCDHA expression at regions of cell-cell contact in aortic smooth muscle and cushion mesenchyme, suggesting potential mechanisms for BAV pathogenesis and aortopathy. Together, these findings indicate common variants causing PCDHA deficiency play a significant role in the genetic etiology of common and rare LVOTO-CHD.

Genetic Etiology of Left-Sided Obstructive Heart Lesions: A Story in Development

Congenital heart disease is the most common congenital defect observed in newborns. Within the spectrum of congenital heart disease are left‐sided obstructive lesions (LSOLs), which include hypoplastic left heart syndrome, aortic stenosis, bicuspid aortic valve, coarctation of the aorta, and interrupted aortic arch. These defects can arise in isolation or as a component of a defined syndrome; however, nonsyndromic defects are often observed in multiple family members and associated with high sibling recurrence risk. This clear evidence for a heritable basis has driven a lengthy search for disease‐causing variants that has uncovered both rare and common variants in genes that, when perturbed in cardiac development, can result in LSOLs. Despite advancements in genetic sequencing platforms and broadening use of exome sequencing, the currently accepted LSOL‐associated genes explain only 10% to 20% of patients. Further, the combinatorial effects of common and rare variants as a cause of LSOLs are emerging. In this review, we highlight the genes and variants associated with the different LSOLs and discuss the strengths and weaknesses of the present genetic associations. Furthermore, we discuss the research avenues needed to bridge the gaps in our current understanding of the genetic basis of nonsyndromic congenital heart disease.

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.

Genetics in bicuspid aortic valve disease: Where are we?

Bicuspid aortic valve (BAV) is the most common congenital heart defect, found in up to 2% of the population and associated with a 30% lifetime risk of complications. BAV is inherited as an autosomal dominant trait with incomplete penetrance and variable expressivity due to a complex genetic architecture that involves many interacting genes. In this review, we highlight the current state of knowledge about BAV genetics, principles and methods for BAV gene discovery, clinical applications of BAV genetics, and important future directions.

The genetic workup for structural congenital heart disease

Congenital heart disease (CHD) is the most prevalent birth defect and is the result of multiple etiologies including genetic and environmental causes. This article reviews the genetic workup for structural CHD in the clinical setting, beginning with CHD epidemiology and etiology and then moving to genetic testing, clinical evaluation, and genetic counseling. An algorithm is presented as a guide to genetic test selection, and available tests are explained with their respective advantages and limitations. Finally, future advances are discussed. As this review focuses on structural heart disease, isolated cardiomyopathies, inherited primary arrhythmia syndromes and aortopathies are not discussed.

Familial co-occurrence of congenital heart defects follows distinct patterns

Aims

Congenital heart defects (CHD) affect almost 1% of all live born children and the number of adults with CHD is increasing. In families where CHD has occurred previously, estimates of recurrence risk, and the type of recurring malformation are important for counselling and clinical decision-making, but the recurrence patterns in families are poorly understood. We aimed to determine recurrence patterns, by investigating the co-occurrences of CHD in 1163 families with known malformations, comprising 3080 individuals with clinically confirmed diagnosis.

Methods and results

We calculated rates of concordance and discordance for 41 specific types of malformations, observing a high variability in the rates of concordance and discordance. By calculating odds ratios for each of 1640 pairs of discordant lesions observed between affected family members, we were able to identify 178 pairs of malformations that co-occurred significantly more or less often than expected in families. The data show that distinct groups of cardiac malformations co-occur in families, suggesting influence from underlying developmental mechanisms. Analysis of human and mouse susceptibility genes showed that they were shared in 19% and 20% of pairs of co-occurring discordant malformations, respectively, but none of malformations that rarely co-occur, suggesting that a significant proportion of co-occurring lesions in families is caused by overlapping susceptibility genes.

Conclusion

Familial CHD follow specific patterns of recurrence, suggesting a strong influence from genetically regulated developmental mechanisms. Co-occurrence of malformations in families is caused by shared susceptibility genes.

Hypoplastic Left Heart Syndrome: An Overview for Primary Care Providers

Hypoplastic left heart syndrome is one of the most complex congenital heart diseases and requires several cardiac surgeries for survival. The diagnosis is usually established prenatally or shortly after birth. Each stage of surgery poses a unique hemodynamic situation that requires deeper understanding to manage common pediatric problems such as dehydration and respiratory infections. Careful multidisciplinary involvement in the care of these complex patients is improving their outcome; however, morbidity and mortality are still substantial. In this review, we focus on the hemodynamic aspects of various surgical stages that a primary care provider should know to manage these challenging patients.

Left ventricular outflow tract obstruction: Uptake of familial cardiac screening and parental knowledge from a single tertiary care center

Left ventricular outflow tract obstruction (LVOTO) malformations exhibit higher heritability than other cardiac lesions and cardiac screening is encouraged for first-degree relatives. This study sought to determine the uptake of familial cardiac screening in families with an infant with an LVOTO and assess parental knowledge regarding genetics and heritability of LVOTO. A chart review of the period 2010-2015 identified 69 families who received genetic counseling regarding a diagnosis of LVOTO in an infant. Surveys assessing familial cardiac screening and parental knowledge were completed by a parent in 24 families (completion rate of 35%). Forty percent (36/89) of all at-risk first-degree family members completed cardiac screening. The presence of additional congenital malformations in the affected infant was the only significant factor reducing the uptake of familial cardiac screening (p = 0.003). The reported uptake of screening for subsequent at-risk pregnancies was 11/12 (92%) compared to 25/77 (32%) of living at-risk relatives. Survey respondents answered seven knowledge questions with an average score of 5.2 and all correctly identified that LVOTO can run in families. Uptake of familial cardiac screening is occurring in less than half of at-risk individuals, despite parents demonstrating basic knowledge and receiving genetic counseling. Follow-up counseling in the outpatient setting to review familial screening recommendations should be considered to increase uptake and optimize outcomes.

The Genetic Landscape of Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is one of the most lethal congenital heart defects, and remains clinically challenging. While surgical palliation allows most HLHS patients to survive their critical heart disease with a single-ventricle physiology, many will suffer heart failure, requiring heart transplantation as the only therapeutic course. Current paradigm suggests HLHS is largely of hemodynamic origin, but recent findings from analysis of the first mouse model of HLHS showed intrinsic cardiomyocyte proliferation and differentiation defects underlying the left ventricular (LV) hypoplasia. The findings of similar defects of lesser severity in the right ventricle suggest this could contribute to the heart failure risks in surgically palliated HLHS patients. Analysis of 8 independent HLHS mouse lines showed HLHS is genetically heterogeneous and multigenic in etiology. Detailed analysis of the Ohia mouse line accompanied by validation studies in CRISPR gene-targeted mice revealed a digenic etiology for HLHS. Mutation in Sap130, a component of the HDAC repressor complex, was demonstrated to drive the LV hypoplasia, while mutation in Pcdha9, a protocadherin cell adhesion molecule played a pivotal role in the valvular defects associated with HLHS. Based on these findings, we propose a new paradigm in which complex CHD such as HLHS may arise in a modular fashion, mediated by multiple mutations. The finding of intrinsic cardiomyocyte defects would suggest hemodynamic intervention may not rescue LV growth. The profound genetic heterogeneity and oligogenic etiology indicated for HLHS would suggest that the genetic landscape of HLHS may be complex and more accessible in clinical studies built on a familial study design.

EDUCATIONAL SERIES IN CONGENITAL HEART DISEASE: Congenital left-sided heart obstruction

Congenital obstruction of the left ventricular outflow tract remains a significant problem and multilevel obstruction can often coexist. Obstruction can take several morphological forms and may involve the subvalvar, valvar or supravalvar portion of the aortic valve complex. Congenital valvar stenosis presenting in the neonatal period represents a spectrum of disorders ranging from the hypoplastic left heart syndrome to almost normal hearts. Treatment options vary dependent on the severity of the left ventricular outflow tract obstruction (LVOTO) and the variable degree of left ventricular hypoplasia as well as the associated lesions such as arch hypoplasia and coarctation.

Familial Screening for Left-Sided Congenital Heart Disease: What Is the Evidence? What Is the Cost?

Since the American Heart Association’s recommendation for familial screening of adults with congenital heart disease for bicuspid aortic valve, similar recommendations for other left-sided heart defects, such as hypoplastic left heart syndrome (HLHS), have been proposed. However, defining at-risk populations for these heart defects based on genetics is less straightforward due to the wide variability of inheritance patterns and non-genetic influences such as environmental and lifestyle factors. We discuss whether there is sufficient evidence to standardize echocardiographic screening for first-degree relatives of children diagnosed with HLHS. Due to variations in the inclusion of cardiac anomalies linked to HLHS and the identification of asymptomatic individuals with cardiac malformations, published studies are open to interpretation. We conclude that familial aggregation of obstructive left-sided congenital heart lesions in families with history of HLHS is not supported and recommend that additional screening should adopt a more conservative definition of what truly constitutes this heart defect. More thorough consideration is needed before embracing familial screening recommendations of families of patients with HLHS, since this could inflict serious costs on healthcare infrastructure and further burden affected families both emotionally and financially.

Relationship of Echocardiographic Z Scores Adjusted for Body Surface Area to Age, Sex, Race, and Ethnicity: The Pediatric Heart Network Normal Echocardiogram Database

BACKGROUND

Published nomograms of pediatric echocardiographic measurements are limited by insufficient sample size to assess the effects of age, sex, race, and ethnicity. Variable methodologies have resulted in a wide range of Z scores for a single measurement. This multicenter study sought to determine Z scores for common measurements adjusted for body surface area (BSA) and stratified by age, sex, race, and ethnicity.

METHODS AND RESULTS

Data collected from healthy nonobese children ≤18 years of age at 19 centers with a normal echocardiogram included age, sex, race, ethnicity, height, weight, echocardiographic images, and measurements performed at the Core Laboratory. Z score models involved indexed parameters (X/BSAα) that were normally distributed without residual dependence on BSA. The models were tested for the effects of age, sex, race, and ethnicity. Raw measurements from models with and without these effects were compared, and <5% difference was considered clinically insignificant because interobserver variability for echocardiographic measurements are reported as ≥5% difference. Of the 3566 subjects, 90% had measurable images. Appropriate BSA transformations (BSAα) were selected for each measurement. Multivariable regression revealed statistically significant effects by age, sex, race, and ethnicity for all outcomes, but all effects were clinically insignificant based on comparisons of models with and without the effects, resulting in Z scores independent of age, sex, race, and ethnicity for each measurement.

CONCLUSIONS

Echocardiographic Z scores based on BSA were derived from a large, diverse, and healthy North American population. Age, sex, race, and ethnicity have small effects on the Z scores that are statistically significant but not clinically important.

Whole exome sequencing in 342 congenital cardiac left sided lesion cases reveals extensive genetic heterogeneity and complex inheritance patterns

BACKGROUND

Left-sided lesions (LSLs) account for an important fraction of severe congenital cardiovascular malformations (CVMs). The genetic contributions to LSLs are complex, and the mutations that cause these malformations span several diverse biological signaling pathways: TGFB, NOTCH, SHH, and more. Here, we use whole exome sequence data generated in 342 LSL cases to identify likely damaging variants in putative candidate CVM genes.

METHODS

Using a series of bioinformatics filters, we focused on genes harboring population-rare, putative loss-of-function (LOF), and predicted damaging variants in 1760 CVM candidate genes constructed a priori from the literature and model organism databases. Gene variants that were not observed in a comparably sequenced control dataset of 5492 samples without severe CVM were then subjected to targeted validation in cases and parents. Whole exome sequencing data from 4593 individuals referred for clinical sequencing were used to bolster evidence for the role of candidate genes in CVMs and LSLs.

RESULTS

Our analyses revealed 28 candidate variants in 27 genes, including 17 genes not previously associated with a human CVM disorder, and revealed diverse patterns of inheritance among LOF carriers, including 9 confirmed de novo variants in both novel and newly described human CVM candidate genes (ACVR1, JARID2, NR2F2, PLRG1, SMURF1) as well as established syndromic CVM genes (KMT2D, NF1, TBX20, ZEB2). We also identified two genes (DNAH5, OFD1) with evidence of recessive and hemizygous inheritance patterns, respectively. Within our clinical cohort, we also observed heterozygous LOF variants in JARID2 and SMAD1 in individuals with cardiac phenotypes, and collectively, carriers of LOF variants in our candidate genes had a four times higher odds of having CVM (odds ratio = 4.0, 95% confidence interval 2.5-6.5).

CONCLUSIONS

Our analytical strategy highlights the utility of bioinformatic resources, including human disease records and model organism phenotyping, in novel gene discovery for rare human disease. The results underscore the extensive genetic heterogeneity underlying non-syndromic LSLs, and posit potential novel candidate genes and complex modes of inheritance in this important group of birth defects.

Cardiac, mandibular and thymic phenotypical association indicates that cranial neural crest underlies bicuspid aortic valve formation in hamsters

Bicuspid aortic valve (BAV) is the most prevalent human congenital cardiac malformation. It may appear isolated, associated with other cardiovascular malformations, or forming part of syndromes. Cranial neural crest (NC) defects are supposed to be the cause of the spectrum of disorders associated with syndromic BAV. Experimental studies with an inbred hamster model of isolated BAV showed that alterations in the migration or differentiation of the cardiac NC cells in the embryonic cardiac outflow tract are most probably responsible for the development of this congenital valvular defect. We hypothesize that isolated BAV is not the result of local, but of early alterations in the behavior of the NC cells, thus also affecting other cranial NC-derived structures. Therefore, we tested whether morphological variation of the aortic valve is linked to phenotypic variation of the mandible and the thymus in the hamster model of isolated BAV, compared to a control strain. Our results show significant differences in the size and shape of the mandible as well as in the cellular composition of the thymus between the two strains, and in mandible shape regarding the morphology of the aortic valve. Given that both the mandible and the thymus are cranial NC derivatives, and that the cardiac NC belongs to the cephalic domain, we propose that the causal defect leading to isolated BAV during embryonic development is not restricted to local alterations of the cardiac NC cells in the cardiac outflow tract, but it is of pleiotropic or polytopic nature. Our results suggest that isolated BAV may be the forme fruste of a polytopic syndrome involving the cranial NC in the hamster model and in a proportion of affected patients.

Genetic Bases of Bicuspid Aortic Valve: The Contribution of Traditional and High-Throughput Sequencing Approaches on Research and Diagnosis

Bicuspid aortic valve (BAV) is a common (0.5-2.0% of general population) congenital heart defect with increased prevalence of aortic dilatation and dissection. BAV has an autosomal dominant inheritance with reduced penetrance and variable expressivity. BAV has been described as an isolated trait or associated with syndromic conditions [e.g., Marfan Marfan syndrome or Loeys-Dietz syndrome (MFS, LDS)]. Identification of a syndromic condition in a BAV patient is clinically relevant to personalize aortic surgery indication. A 4-fold increase in BAV prevalence in a large cohort of unrelated MFS patients with respect to general population was reported, as well as in LDS patients (8-fold). It is also known that BAV is more frequent in patients with thoracic aortic aneurysm (TAA) related to mutations in ACTA2, FBN1, and TGFBR2 genes. Moreover, in 8 patients with BAV and thoracic aortic dilation, not fulfilling the clinical criteria for MFS, FBN1 mutations in 2/8 patients were identified suggesting that FBN1 or other genes involved in syndromic conditions correlated to aortopathy could be involved in BAV. Beyond loci associated to syndromic disorders, studies in humans and animal models evidenced/suggested the role of further genes in non-syndromic BAV. The transcriptional regulator NOTCH1 has been associated with the development and acceleration of calcium deposition. Genome wide marker-based linkage analysis demonstrated a linkage of BAV to loci on chromosomes 18, 5, and 13q. Recently, a role for GATA4/5 in aortic valve morphogenesis and endocardial cell differentiation has been reported. BAV has also been associated with a reduced UFD1L gene expression or involvement of a locus containing AXIN1/PDIA2. Much remains to be understood about the genetics of BAV. In the last years, high-throughput sequencing technologies, allowing the analysis of large number of genes or entire exomes or genomes, progressively became available. The latter issue together with the development of "BigData" analysis methods improving their interpretation and integration with clinical data represents a promising opportunity to increase the disease knowledge and diagnosis in monogenic and multifactorial complex traits. This review summarized the main knowledge on the BAV genetic bases, the role of genetic diagnosis in BAV patient managements and the crucial challenges for the comprehension of genetics of BAV in research and diagnosis.

Assessment of large copy number variants in patients with apparently isolated congenital left-sided cardiac lesions reveals clinically relevant genomic events

Congenital left-sided cardiac lesions (LSLs) are a significant contributor to the mortality and morbidity of congenital heart disease (CHD). Structural copy number variants (CNVs) have been implicated in LSL without extra-cardiac features; however, non-penetrance and variable expressivity have created uncertainty over the use of CNV analyses in such patients. High-density SNP microarray genotyping data were used to infer large, likely-pathogenic, autosomal CNVs in a cohort of 1,139 probands with LSL and their families. CNVs were molecularly confirmed and the medical records of individual carriers reviewed. The gene content of novel CNVs was then compared with public CNV data from CHD patients. Large CNVs (>1 MB) were observed in 33 probands (∼3%). Six of these were de novo and 14 were not observed in the only available parent sample. Associated cardiac phenotypes spanned a broad spectrum without clear predilection. Candidate CNVs were largely non-recurrent, associated with heterozygous loss of copy number, and overlapped known CHD genomic regions. Novel CNV regions were enriched for cardiac development genes, including seven that have not been previously associated with human CHD. CNV analysis can be a clinically useful and molecularly informative tool in LSLs without obvious extra-cardiac defects, and may identify a clinically relevant genomic disorder in a small but important proportion of these individuals.

Autosomal and X chromosome structural variants are associated with congenital heart defects in Turner syndrome: The NHLBI GenTAC registry

Turner Syndrome (TS) is a developmental disorder caused by partial or complete loss of one sex chromosome. Bicuspid aortic valve and other left-sided congenital heart lesions (LSL), including thoracic aortic aneurysms and acute aortic dissections, are 30-50 times more frequent in TS than in the general population. In 454 TS subjects, we found that LSL are significantly associated with reduced dosage of Xp genes and increased dosage of Xq genes. We also showed that genome-wide copy number variation is increased in TS and identify a common copy number variant (CNV) in chromosome 12p13.31 that is associated with LSL with an odds ratio of 3.7. This CNV contains three protein-coding genes (SLC2A3, SLC2A14, and NANOGP1) and was previously implicated in congenital heart defects in the 22q11 deletion syndrome. In addition, we identified a subset of rare and recurrent CNVs that are also enriched in non-syndromic BAV cases. These observations support our hypothesis that X chromosome and autosomal variants affecting cardiac developmental genes may interact to cause the increased prevalence of LSL in TS. © 2016 Wiley Periodicals, Inc.

Impact of MYH6 variants in hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) is a clinically and anatomically severe form of congenital heart disease (CHD). Although prior studies suggest that HLHS has a complex genetic inheritance, its etiology remains largely unknown. The goal of this study was to characterize a risk gene in HLHS and its effect on HLHS etiology and outcome. We performed next-generation sequencing on a multigenerational family with a high prevalence of CHD/HLHS, identifying a rare variant in the α-myosin heavy chain (MYH6) gene. A case-control study of 190 unrelated HLHS subjects was then performed and compared with the 1000 Genomes Project. Damaging MYH6 variants, including novel, missense, in-frame deletion, premature stop, de novo, and compound heterozygous variants, were significantly enriched in HLHS cases (P < 1 × 10⁻⁵). Clinical outcomes analysis showed reduced transplant-free survival in HLHS subjects with damaging MYH6 variants (P < 1 × 10⁻²). Transcriptome and protein expression analyses with cardiac tissue revealed differential expression of cardiac contractility genes, notably upregulation of the β-myosin heavy chain (MYH7) gene in subjects with MYH6 variants (P < 1 × 10⁻³). We subsequently used patient-specific induced pluripotent stem cells (iPSCs) to model HLHS in vitro. Early stages of in vitro cardiomyogenesis in iPSCs derived from two unrelated HLHS families mimicked the increased expression of MYH7 observed in vivo (P < 1 × 10⁻²), while revealing defective cardiomyogenic differentiation. Rare, damaging variants in MYH6 are enriched in HLHS, affect molecular expression of contractility genes, and are predictive of poor outcome. These findings indicate that the etiology of MYH6-associated HLHS can be informed using iPSCs and suggest utility in future clinical applications.

Bicuspid Aortic Valve: a Review with Recommendations for Genetic Counseling

Bicuspid aortic valve (BAV) is the most common congenital heart defect and falls in the spectrum of left-sided heart defects, also known as left ventricular outflow tract obstructive (LVOTO) defects. BAV is often identified in otherwise healthy, asymptomatic individuals, but it is associated with serious long term health risks including progressive aortic valve disease (stenosis or regurgitation) and thoracic aortic aneurysm and dissection. BAV and other LVOTO defects have high heritability. Although recommendations for cardiac screening of BAV in at-risk relatives exist, there are no standard guidelines for providing genetic counseling to patients and families with BAV. This review describes current knowledge of BAV and associated aortopathy and provides guidance to genetic counselors involved in the care of patients and families with these malformations. The heritability of BAV and recommendations for screening are highlighted. While this review focuses specifically on BAV, the principles are applicable to counseling needs for other LVOTO defects.

A genome-wide association study of congenital cardiovascular left-sided lesions shows association with a locus on chromosome 20

Congenital heart defects involving left-sided lesions (LSLs) are relatively common birth defects with substantial morbidity and mortality. Previous studies have suggested a high heritability with a complex genetic architecture, such that only a few LSL loci have been identified. We performed a genome-wide case-control association study to address the role of common variants using a discovery cohort of 778 cases and 2756 controls. We identified a genome-wide significant association mapping to a 200 kb region on chromosome 20q11 [P= 1.72 × 10^-8 for rs3746446; imputed Single Nucleotide Polymorphism (SNP) rs6088703 P= 3.01 × 10^-9, odds ratio (OR)= 1.6 for both]. This result was supported by transmission disequilibrium analyses using a subset of 541 case families (lowest P in region= 4.51 × 10^-5, OR= 1.5). Replication in a cohort of 367 LSL cases and 5159 controls showed nominal association (P= 0.03 for rs3746446) resulting in P= 9.49 × 10^-9 for rs3746446 upon meta-analysis of the combined cohorts. In addition, a group of seven SNPs on chromosome 1q21.3 met threshold for suggestive association (lowest P= 9.35 × 10^-7 for rs12045807). Both regions include genes involved in cardiac development-MYH7B/miR499A on chromosome 20 and CTSK, CTSS and ARNT on chromosome 1. Genome-wide heritability analysis using case-control genotyped SNPs suggested that the mean heritability of LSLs attributable to common variants is moderately high ([Formula: see text] range= 0.26-0.34) and consistent with previous assertions. These results provide evidence for the role of common variation in LSLs, proffer new genes as potential biological candidates, and give further insight to the complex genetic architecture of congenital heart disease.

Familial Incidence of Cardiovascular Malformations in Hypoplastic Left Heart Syndrome

Obstructive left-sided congenital heart lesions exhibit familial clustering, and familial echocardiographic screening for bicuspid aortic valve has become standard practice. Hypoplastic left heart syndrome (HLHS) is a severe left-sided obstructive lesion; however, familial screening is not universally recommended. The purpose of this study was to define the incidence of cardiovascular malformations (CVMs) in first-degree relatives of HLHS probands. First-degree relatives were screened for CVM by transthoracic echocardiography. Screening was completed in 152 family members (97 parents and 55 siblings) of 52 probands. Of these, 17 of 152 (11%) had CVM. Anomalies detected included: bicuspid aortic valve in 5 (3%), isolated dilated ascending aorta in 4 (3%), coarctation of the aorta in 1, partial anomalous pulmonary venous connection in 1, anomalous, intramural coronary artery in 1, bicuspid pulmonary valve in 1, and other anomalies in 4. Most were previously undiagnosed (11 of 17, 65%). Fourteen of 52 families (27%) had ≥1 relative with CVM. Overall, 7 of 55 siblings (13%), 5 of 46 fathers (11%) and 5 of 51 mothers (10%) had CVM. Although the incidence of CVM in first-degree relatives of HLHS probands was lower in this cohort than previously reported, it remained substantial, with at least one additional member having CVM in 27% of families. The frequent occurrence of undiagnosed CVM highlights the importance of routine familial screening in HLHS. In fact, even if screening was done in childhood, it may be appropriate to screen again in the third or fourth decade to exclude isolated enlargement of the ascending aorta.

Genome-Wide Association Study of Down Syndrome-Associated Atrioventricular Septal Defects

The goal of this study was to identify the contribution of common genetic variants to Down syndrome−associated atrioventricular septal defect, a severe heart abnormality. Compared with the euploid population, infants with Down syndrome, or trisomy 21, have a 2000-fold increased risk of presenting with atrioventricular septal defects. The cause of this increased risk remains elusive. Here we present data from the largest heart study conducted to date on a trisomic background by using a carefully characterized collection of individuals from extreme ends of the phenotypic spectrum. We performed a genome-wide association study using logistic regression analysis on 452 individuals with Down syndrome, consisting of 210 cases with complete atrioventricular septal defects and 242 controls with structurally normal hearts. No individual variant achieved genome-wide significance. We identified four disomic regions (1p36.3, 5p15.31, 8q22.3, and 17q22) and two trisomic regions on chromosome 21 (around PDXK and KCNJ6 genes) that merit further investigation in large replication studies. Our data show that a few common genetic variants of large effect size (odds ratio >2.0) do not account for the elevated risk of Down syndrome−associated atrioventricular septal defects. Instead, multiple variants of low-to-moderate effect sizes may contribute to this elevated risk, highlighting the complex genetic architecture of atrioventricular septal defects even in the highly susceptible Down syndrome population.

Echocardiography screening of siblings of children with bicuspid aortic valve

BACKGROUND AND OBJECTIVE

Left heart defects, such as bicuspid aortic valve (BAV), are heritable. Consensus guidelines have recommended echocardiographic screening of first-degree relatives. The utility of this approach in siblings of children with BAV is not known. The objective of this study is to evaluate the yield of routine screening of siblings of children with BAV and undertake an economic analysis of this practice.

METHODS

Siblings of children with BAV who underwent echocardiographic screening in a single pediatric cardiology practice were identified. The anatomic features and hemodynamics of siblings newly diagnosed with BAV were recorded. A Markov model was constructed to determine cost-effectiveness ratios, and sensitivity analyses were performed.

RESULTS

There were 207 screened siblings of 181 children with BAV. The median age at screening was 7 years. BAV was identified in 21 (10.1%) of siblings screened. The median peak Doppler gradient was 18 mm Hg. Aortic insufficiency was mild or less in all. The mean cost to diagnose BAV in a sibling was $2109 per new case found. The estimated mean cost to avert a single aortic dissection in the third or fourth decade of life was $363 911. The estimated cost per life-year saved was $74 884 and ranged from $17 461 to $1 136 536 in sensitivity analysis.

CONCLUSIONS

Echo screening among siblings of those with BAV is effective and inexpensive and may lower the risk of the complications of such as dissection, although it comes at a moderate cost relative to benefits gained. Screening of siblings should be incorporated into clinical care.

Genetic basis of congenital cardiovascular malformations

Cardiovascular malformations are a singularly important class of birth defects and due to dramatic improvements in medical and surgical care, there are now large numbers of adult survivors. The etiologies are complex, but there is strong evidence that genetic factors play a crucial role. Over the last 15 years there has been enormous progress in the discovery of causative genes for syndromic heart malformations and in rare families with Mendelian forms. The rapid characterization of genomic disorders as major contributors to congenital heart defects is also notable. The genes identified encode many transcription factors, chromatin regulators, growth factors and signal transduction proteins- all unified by their required roles in normal cardiac development. Genome-wide sequencing of the coding regions promises to elucidate genetic causation in several disorders affecting cardiac development. Such comprehensive studies evaluating both common and rare variants would be essential in characterizing gene-gene interactions, as well as in understanding the gene-environment interactions that increase susceptibility to congenital heart defects.

Aortic stenosis at young adult age

Aortic stenosis at young adult age is usually the result of a stenotic bicuspid aortic valve, which is the most common cardiac congenital anomaly. In clinical practice, exercise and pregnancy are important topics. Furthermore, the timing of intervention is under debate, as little information is available on the natural history and outcome after aortic valve replacement in these young adults. In older patients, there is a trend towards earlier intervention. With the increased knowledge of the pathophysiology of aortic stenosis, studies have focused on the dilatation of the ascending aorta with risk of dissection. Recently, it has been suggested that pharmacologic treatment of aortic stenosis could be beneficial for these young adults.

Screening of families of patients with left-sided cardiovascular anomalies

BACKGROUND

There is increasing evidence of clustering of certain cardiac anomalies in some families. The frequency and echocardiographic features of such anomalies among the relatives of patients with bicuspid aortic valve (BAV) or other left-sided cardiovascular anomalies (LSCA) were evaluated.

METHODS

The patients with BAV or any other LSCA and their relatives were enrolled in the study. They underwent an echocardiographic examination. The probands were assessed in three groups: BAV, BAV + coarctation of aorta (CoA), and other LSCA. Their relatives were also grouped and evaluated accordingly. The echocardiographic measurements were standardized by Z-scores.

RESULTS

Eighty-six probands and 261 relatives were evaluated. The numbers of the patients in the BAV, BAV + CoA, and other LSCA group were 52, 14, and 20, respectively. Any LSCA was determined in 17 (6.5%) of the relatives. Thirteen (5%) had aortic dilatation and the remainder (1.5%) had BAV. Accordingly, BAV incidence among relatives of patients with BAV was found to be 1.9%. A second individual with an LSCA was observed in 12.8% of 86 families investigated. The frequencies of aortic stenosis, aortic regurgitation, aortic stenosis + aortic regurgitation, and aortic dilatation in the patients with BAV were found to be 37.9%, 53%, 25.8% and 48.5%, respectively. In contrast to previous reports, no enlargement was observed in the pulmonary arteries of BAV patients.

CONCLUSIONS

BAV and other LSCA are of clinical significance. Because the clustering of LSCA in some families is observed, we recommend echocardiographic screening of those relatives. If this is not possible, at least it should be achieved for BAV patients.

Family-based studies to identify genetic variants that cause congenital heart defects

Congenital heart defects (CHDs) are the most common congenital abnormalities. Analysis of large multigenerational families has led to the identification of a number of genes for CHDs. However, identifiable variations in these genes are the cause of a small proportion of cases of CHDs, suggesting significant genetic heterogeneity. In addition, large families with CHDs are rare, making the identification of additional genes difficult. Next-generation sequencing technologies will provide an opportunity to identify more genes in the future. However, the significant genetic variation between individuals will present a challenge to distinguish between 'pathogenic' and 'benign' variants. We have demonstrated that the analysis of multiple individuals in small families using combinations of algorithms can reduce the number of candidate variants to a small, manageable number. Thus, the analysis of small nuclear families or even distantly related 'sporadic' cases may begin to uncover the 'dark matter' of CHD genetics.

The Role of the Geneticist and Genetic Counselor in an ACHD Clinic

There is a growing population of adults with congenital heart disease due to the advancements in surgical repair and medical management. At the same time, the understanding of the genetic basis of both syndromic and isolated congenital heart disease has grown tremendously and is being rapidly translated into changes in clinical care, resulting in an increasing need for incorporation of genetic expertise into the care of adult congenital heart disease patients. Here we review the importance of delivery of genetic information to the adult congenital heart disease population and highlight the shared and distinct roles of clinical geneticists and genetic counselors in provision of services. The adult congenital heart disease patient population has unique needs and clinical geneticists and genetic counselors can play an important role in the diagnostic evaluation and assessment of these patients to provide an accurate etiologic diagnosis and to counsel regarding genetic testing, recurrence risk, family screening, and prenatal diagnosis.

New Genetic Insights into Congenital Heart Disease

There has been remarkable progress in understanding the genetic basis of cardiovascular malformations. Chromosome microarray analysis has provided a new tool to understand the genetic basis of syndromic cardiovascular malformations resulting from microdeletion or microduplication of genetic material, allowing the delineation of new syndromes. Improvements in sequencing technology have led to increasingly comprehensive testing for aortopathy, cardiomyopathy, single gene syndromic disorders, and Mendelian-inherited congenital heart disease. Understanding the genetic etiology for these disorders has improved their clinical recognition and management and led to new guidelines for treatment and family-based diagnosis and surveillance. These new discoveries have also expanded our understanding of the contribution of genetic variation, susceptibility alleles, and epigenetics to isolated congenital heart disease. This review summarizes the current understanding of the genetic basis of syndromic and non-syndromic congenital heart disease and highlights new diagnostic and management recommendations.

Submicroscopic chromosomal copy number variations identified in children with hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS), one of the most severe types of congenital heart disease (CHD), results in significant morbidity and mortality despite surgical palliation. The etiology of HLHS is unknown, but evidence supports genetic contributors. The authors hypothesized that submicroscopic chromosomal abnormalities exist in individuals with HLHS and are more frequent in those with additional birth defects. This study sought to determine the incidence and genomic location of submicroscopic chromosomal abnormalities in HLHS and potentially to identify novel genetic loci that may contribute to the disease. For this study, 43 children with HLHS were recruited and screened together with a control population of 16 subjects using array comparative genomic hybridization, also called chromosomal microarray, for chromosomal copy number variations (CNVs). A statistically greater number of CNVs were found in the HLHS group than in the control group (p < 0.03). The CNVs were predominantly small autosomal deletions and duplications (≤ 60,000 bp). The frequency of unique CNVs, those not previously reported in public databases, did not differ statistically between the HLHS subjects and the control subjects. No difference in the frequency of CNVs was noted between the patients with HLHS and additional anomalies and those with isolated HLHS. The identified CNVs did not harbor potential candidate genes for HLHS, but one microdeletion was located on chromosome 14q23, a genetic locus linked to left-sided CHD. The study data demonstrate that CNVs, specifically those relatively small in size, are more common in subjects with HLHS, but the frequency of large potentially disease-causing CNVs (>480,000 bp) did not differ between the HLHS and control populations.

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.

Association of common variants in ERBB4 with congenital left ventricular outflow tract obstruction defects

BACKGROUND

The left ventricular outflow tract (LVOT) defects aortic valve stenosis (AVS), coarctation of the aorta (COA), and hypoplastic left heart syndrome (HLHS) represent an embryologically related group of congenital cardiovascular malformations. They are common and cause substantial morbidity and mortality. Prior evidence suggests a strong genetic component in their causation.

METHODS

We selected NRG1, ERBB3, and ERBB4 of the epidermal growth factor receptor (EGFR) signaling pathway as candidate genes for investigation of association with LVOT defects based on the importance of this pathway in cardiac development and the phenotypes in knockout mouse models. Single nucleotide polymorphism (SNP) genotyping was performed on 343 affected case-parent trios of European ancestry.

RESULTS

We identified a specific haplotype in intron 3 of ERBB4 that was positively associated with the combined LVOT defects phenotype (p=0.0005) and in each anatomic defect AVS, COA, and HLHS separately. Mutation screening of individuals with an LVOT defect failed to identify a coding sequence or splice site change in ERBB4. RT-PCR on lymphoblastoid cells from LVOT subjects did not show altered splice variant ratios among those homozygous for the associated haplotype.

CONCLUSION

These results suggest ERBB4 is associated with LVOT defects. Further replication will be required in separate cohorts to confirm the consistency of the observed association.

Maternal use of bupropion and risk for congenital heart defects

OBJECTIVE

We sought to determine if maternal bupropion treatment in early pregnancy is associated with congenital heart defects in the infant.

STUDY DESIGN

We conducted a retrospective case-control study of birth defects risk factors. Data on 6853 infants with major heart defects were compared with 5869 control infants born in 1997-2004. Bupropion exposure was defined as any reported use between 1 month before and 3 months after conception.

RESULTS

Mothers of infants with left outflow tract heart defects were more likely to have reported taking bupropion than mothers of control infants (adjusted odds ratio, 2.6; 95% confidence interval, 1.2-5.7; P = .01).

CONCLUSION

We identified a positive association between early pregnancy bupropion use and left outflow tract heart defects; however, the magnitude of the observed increased risk was small. Nevertheless, further studies are needed to confirm these results.

Coarctation of the aorta: evaluation and management

PURPOSE OF REVIEW

Coarctation of the aorta is the discrete narrowing of the proximal descending aorta and is the sixth most common lesion in congenital heart disease. Repair of the coarctation can relieve the obstruction, but recurrent coarctation and future aneurysm formation can occur, and a heightened risk of vascular disease is present. This review focuses on advances in the management of native and previously treated coarctation and provides insights into future vascular risk.

RECENT FINDINGS

Coarctation of the aorta is associated with other left heart obstructive lesions, and advances in the genetic basis of these conditions have been made. Recurrent coarctation and aneurysm formation are common after surgical and endovascular repair of coarctation of the aorta. Endovascular treatment is an acceptable alternative to surgical repair of native and recurrent coarctation. Covered stents and stent grafts can be used to treat arch complications with a low risk of complications. In spite of repair of the obstruction, hypertension persists and appears to be multifactorial due to a variety of factors, including endothelial dysfunction, aortic stiffness, altered arch morphology and increased ventricular stiffness.

SUMMARY

People with previously repaired coarctation of the aorta require long-term surveillance for local complications with aortic imaging and surveillance and management of hypertension to prevent vascular disease.

Variants of folate metabolism genes and risk of left-sided cardiac defects

BACKGROUND

Congenital heart defects (CHDs) are the most common, serious group of birth defects. Although relatively little is known about the causes of these conditions and there are no established prevention strategies, evidence suggests that the risk of CHDs may be related to maternal folate status as well as genetic variants in folate-related genes. Efforts to establish the relationships between these factors and CHD risk have, however, been hampered by a number of factors, including small study sample sizes and phenotypic heterogeneity.

METHODS

The present study examined the relationship between nine genetic variants in eight folate-related genes and a relatively homogeneous group of left-sided cardiac defects in a cohort of 386 case-parent triads. Log-linear analyses were used to assess both maternal and inherited genetic effects.

RESULTS

Analyses of the study data provided marginal evidence that the maternal MTR A2756G (unadjusted p = 0.01) and the inherited BHMT G742A (unadjusted p = 0.06) genotypes influence the risk of this subset of CHDs. However, neither association achieved significance when the false-discovery rate was controlled at 0.05.

CONCLUSIONS

These results, which are based on the largest study sample and most comprehensive assessment of the relationship between left-sided cardiac defects and folate-related genes reported to date, provide little evidence that this subset of CHDs is folate related. However, even larger studies and more comprehensive evaluations of the folate pathway genes are required to fully explore the relationship between folate and left-sided cardiac defects.