Epidemiology of noncomplex left ventricular outflow tract obstruction malformations (aortic valve stenosis, coarctation of the aorta, hypoplastic left heart syndrome) in Texas, 1999-2001

CMR reference values of right ventricular volumetric variables in patients with hypoplastic left heart syndrome

BACKGROUND

Cardiovascular magnetic resonance (CMR) has established itself as the gold standard for serial assessment of systemic right ventricular (RV) performance but due to the lack of standardized RV reference values for HLHS patients, the interpretation of RV volumetric data in HLHS remains difficult. Therefore, this study aimed to close this gap by providing CMR reference values for the systemic RV in HLHS patients.

METHODS

CMR scans of 160 children, adolescents and young adults (age range 2.2 to 25.2 years, 106 males) with HLHS were retrospectively evaluated. All patients were studied following total cavopulmonary connection. Short axis stacks were used to measure RV end-diastolic and end-systolic volumes (RVEDV, RVESV), stroke volume (RVSV), ejection fraction (RVEF) and end-diastolic myocardial mass (RVEDMM). Univariable and multiple linear regression analyses was performed to assess associations between RV parameters and demographic and anthropometric characteristics. Following the results of the regression analysis, reference graphs and tables were created with the LMS-method.

RESULTS

Multiple linear regression analysis showed strong associations between body height and RVEDV, RVESV as well as RVSV. Age was highly associated with RVEDMM. Therefore, percentile curves and tables were created with respect to body height (RVEDV, RVESV, RVSV) and age (RVEDMM). The influence of demographic and anthropometric parameters on RVEF was mild, thus no percentile curves and tables for RVEF are provided.

CONCLUSION

We were able to define CMR reference values for RV volumetric variables for HLHS patients. These data might be useful for the assessment and interpretation of CMR scans in these patients and for research in this field.

Experiences of parents of children with hypoplastic left heart syndrome during their treatment: a qualitative study

AIM

To investigate the opinion and personal experience of parents of children born with Hypoplastic Left Heart Syndrome and what advice they would give to other parents who have to decide between treatment options.

METHODS

We conducted a qualitative, descriptive and retrospective study by means of a survey directed to parents of children born with Hypoplastic Left Heart Syndrome in a tertiary hospital in Buenos Aires (Argentina). Their answers and data regarding medical procedures were analysed.

RESULTS

Parents of thirteen out of sixteen patients with Hypoplastic Left Heart Syndrome were surveyed. Norwood surgery had been performed in all the patients, many had received other procedures, and five had died. In relation to the decision-making process, sixty-one percent of parents would recommend other parents to remain at peace after having done everything possible and 54% would suggest to not feel guilt despite the final result. None of the parents would recommend rejecting surgical treatment and choosing comfort care.

CONCLUSION

The majority of parents of children with Hypoplastic Left Heart Syndrome would recommend continuing with the therapeutic effort in order to feel at peace and reduce feelings of guilt.

Gender differences in congenital heart defects: a narrative review

Background and Objective

Congenital heart defects (CHD) represent the most frequent human birth defects, occurring in almost 1% of all live newborns. Understanding the effects of gender in the prevalence of CHD has a key role in defining personalized prevention, disease identification, prognosis definition and individualized therapeutic strategies. Recently, the attempt to achieve a holistic approach to patients with CHD cannot be separated from accounting for existing gender differences. The main aim of this narrative review is to provide an overview of gender differences in the epidemiology of CHD.

Methods

A standardized research through three electronic databases (PubMed/Scopus/Embase) was performed using a combination of keywords and Medical Subject Headings (MeSH) terms to include congenital heart diseases, gender difference(s), prevalence. Observational, prospective, population based and retrospective studies reporting gender differences in the prevalence of CHD were included. Conference abstracts were excluded as well as studies not written in English language and non-human studies. Further relevant papers were selected by hand-searching of the references list of selected articles.

Key Content and Findings

Search results returned 1,904 papers. Screening articles by title and abstracts resulted in 17 articles for full text review. Of these, 10 were included for analysis and additional 11 articles were included after hand searching review of reference lists. A total of 21 articles were included.

Conclusions

Our narrative review confirms that there is a significant gender variation in specific CHD subgroups. In particular, we summarized the evidence that there is a significantly greater risk for males to be born with severe CHD and for females with milder CHD subtypes. The etiology of the different distribution of CHD among genders is still under investigation and a deeper understanding of how gender influences the risk for CHD is warranted. In the future, a gender-based management of CHD should become an established medical approach.

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.

Risk of Congenital Heart Defects in Offspring of Affected Mothers and Fathers

Background:

Smaller studies have reported a higher offspring risk of congenital heart defects (CHDs) for mothers with CHDs than for fathers with CHDs. In a large population-based study, we investigated whether offspring risk of CHD differed for mothers and fathers with CHDs.

Methods:

All people born in Denmark, 1977 to 2011, with at least 1 registered parent, were included in our cohort (n=2 341 061). Parent-child recurrence of CHDs was evaluated using risk ratios (RRs) comparing risks of CHDs in individuals with and without a parent with a CHD, estimated using log-linear binomial regression.

Results:

The RRs for any CHD in offspring were 5.39 (95% CI, 4.88–5.96) for mothers and 3.04 (95% CI, 2.59–3.57) for fathers affected with any CHD; the ratio of RRs for mothers versus fathers was 1.82 ( P <0.0001). Recurrence RRs for the same cardiac phenotype in parent and offspring were significantly stronger for mothers than for fathers for conotruncal defects (ratio of RRs, 4.98), left ventricular outlet tract obstruction (ratio of RRs, 4.98), and ventricular septal defects (ratio of RRs, 2.51) but not for atrioventricular septal defects (ratio of RRs, 1.06). Birth rates among people with CHDs, relative to the general population, were 18% higher for women than for men, regardless of parental cardiac phenotype.

Conclusions:

Recurrence risks of CHDs were significantly greater in the offspring of affected women than in the offspring of affected men. The excess maternal recurrence risks could not be explained by the slightly higher birth rates in women with CHDs.

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.

Hypoplastic Left Heart Syndrome Across the Lifespan: Clinical Considerations for Care of the Fetus, Child, and Adult

Hypoplastic left heart syndrome (HLHS) is the most common anatomic lesion in children born with single ventricle physiology and is characterized by the presence of a dominant right ventricle and a hypoplastic left ventricle along with small left-sided heart structures. Diagnostic subgroups of HLHS reflect the extent of inflow and outflow obstruction at the aortic and mitral valves, specifically stenosis or atresia. If left unpalliated, HLHS is a uniformly fatal lesion in infancy. Following introduction of the Norwood operation, early survival has steadily improved over the past four decades, mirroring advances in operative and peri-operative management as well as reflecting refinements in patient surveillance and interstage clinical care. Notably, survival following staged palliation has increased from 0% to a 5-year survival of 60-65% for children in some centres. Despite the prevalence of HLHS in childhood with relatively favourable surgical outcomes in contemporary series, this cohort is only now reaching early adult life and longer-term outcomes have yet to be elucidated. In this article we focus on contemporary clinical management strategies for patients with HLHS across the lifespan, from fetal to adult life. Nomenclature and diagnostic considerations are discussed and current literature pertaining to putative genetic etiologies is reviewed. The spectrum of fetal and pediatric interventional strategies, both percutaneous and surgical, are described. Clinical, patient-reported and neurodevelopmental outcomes of HLHS are delineated. Finally, note is made of current areas of clinical uncertainty and suggested directions for future research are highlighted.

Maternal folic acid supplementation mediates the associations between maternal socioeconomic status and congenital heart diseases in offspring

Low maternal socioeconomic status (SES) is considered as a risk factor of congenital heart diseases (CHDs) in offspring. However, the pathways underpinning the SES-CHDs associations are unclear. We assessed if first trimester maternal folic acid supplementation (FAS) is a mediator of the SES-CHDs associations. This case-control study included 8379 CHD cases and 6918 CHD-free controls from 40 participating centers in Guangdong, Southern China, 2004-2016. All fetuses were screened for CHDs using ultrasound and cases were confirmed by echocardiogram. We collected SES and FAS information during face-to-face interview by obstetricians using a structured questionnaire. Low SES was defined as education attainment <12 years, household individual income <3000 Chinese Yuan/person/month or unemployment. FAS referred to at least 0.4 mg of daily folic acid intake over 5 days/week continuously. We used causal mediation analysis to estimate the direct, indirect and proportion mediated by FAS on the SES-CHDs associations adjusted for confounders. Both low maternal income and education were significantly associated with increased risks of CHDs and lower prevalence of FAS. Low maternal FAS prevalence mediated 10% [95%CI:5%,13%] and 3% [95%CI:1%,5%] of the maternal low income-CHDs and the maternal low education-CHDs associations, respectively. In addition, FAS mediated the highest proportion of the associations between income and multiple critical CHDs [46.9%, 95%CI:24.7%,77%] and conotruncal defects [31.5%, 95%CI:17.1%,52.0%], respectively. Maternal FAS partially mediated the SES-CHDs associations, especially among the most critical and common CHDs. Promoting FAS in low SES women of childbearing age may be a feasible intervention to help prevent CHDs.

Social determinants of health and outcomes for children and adults with congenital heart disease: a systematic review

BACKGROUND

Social determinants of health (SDH) can substantially impact health outcomes. A systematic review, however, has never been conducted on associations of SDH with congenital heart disease (CHD) outcomes. The aim, therefore, was to conduct such a systematic review.

METHODS

Seven databases were searched through May 2020 to identify articles on SDH associations with CHD. SDH examined included poverty, uninsurance, housing instability, parental educational attainment, immigration status, food insecurity, and transportation barriers. Studies were independently selected and coded by two researchers based on the PICO statement.

RESULTS

The search generated 3992 citations; 88 were included in the final database. SDH were significantly associated with a lower likelihood of fetal CHD diagnosis, higher CHD incidence and prevalence, increased infant mortality, adverse post-surgical outcomes (including hospital readmission and death), decreased healthcare access (including missed appointments, no shows, and loss to follow-up), impaired neurodevelopmental outcomes (including IQ and school performance) and quality of life, and adverse outcomes for adults with CHD (including endocarditis, hospitalization, and death).

CONCLUSIONS

SDH are associated with a wide range of adverse outcomes for fetuses, children, and adults with CHD. SDH screening and referral to appropriate services has the potential to improve outcomes for CHD patients across the lifespan.

IMPACT

Social determinants of health (SDH) are associated with a wide range of adverse outcomes for fetuses, children, and adults with congenital heart disease (CHD). This is the first systematic review (to our knowledge) on associations of SDH with congenital heart disease CHD outcomes. SDH screening and referral to appropriate services has the potential to improve outcomes for CHD patients across the lifespan.

Patient-specific genomics and cross-species functional analysis implicate LRP2 in hypoplastic left heart syndrome

Congenital heart diseases (CHDs), including hypoplastic left heart syndrome (HLHS), are genetically complex and poorly understood. Here, a multidisciplinary platform was established to functionally evaluate novel CHD gene candidates, based on whole-genome and iPSC RNA sequencing of a HLHS family-trio. Filtering for rare variants and altered expression in proband iPSCs prioritized 10 candidates. siRNA/RNAi-mediated knockdown in healthy human iPSC-derived cardiomyocytes (hiPSC-CM) and in developing Drosophila and zebrafish hearts revealed that LDL receptor-related protein LRP2 is required for cardiomyocyte proliferation and differentiation. Consistent with hypoplastic heart defects, compared to patents the proband's iPSC-CMs exhibited reduced proliferation. Interestingly, rare, predicted-damaging LRP2 variants were enriched in a HLHS cohort; however, understanding their contribution to HLHS requires further investigation. Collectively, we have established a multi-species high-throughput platform to rapidly evaluate candidate genes and their interactions during heart development, which are crucial first steps toward deciphering oligogenic underpinnings of CHDs, including hypoplastic left hearts.

Contribution of single-gene defects to congenital cardiac left-sided lesions in the prenatal setting

OBJECTIVES

To explore the contribution of single-gene defects to the genetic cause of cardiac left-sided lesions (LSLs), and to evaluate the incremental diagnostic yield of whole-exome sequencing (WES) for single-gene defects in fetuses with LSLs without aneuploidy or a pathogenic copy-number variant (pCNV).

METHODS

Between 10 April 2015 and 30 October 2018, we recruited 80 pregnant women diagnosed with a LSL who had termination of pregnancy and genetic testing. Eligible LSLs were aortic valve atresia or stenosis, coarctation of the aorta, mitral atresia or stenosis and hypoplastic left heart syndrome (HLHS). CNV sequencing (CNV-seq) and WES were performed sequentially on specimens from these fetuses and their parents. CNV-seq was used to identify aneuploidies and pCNVs, while WES was used to identify diagnostic genetic variants in cases without aneuploidy or pCNV.

RESULTS

Of 80 pregnancies included in the study, 27 (33.8%) had a genetic diagnosis. CNV-seq analysis identified six (7.5%) fetuses with aneuploidy and eight (10.0%) with pCNVs. WES analysis of the remaining 66 cases revealed diagnostic genetic variants in 13 (19.7%) cases, indicating that the diagnostic yield of WES for the entire cohort was 16.3% (13/80). KMT2D was the most frequently mutated gene (7/66 (10.6%)) in fetuses with LSL without aneuploidy or pCNVs, followed by NOTCH1 (4/66 (6.1%)). HLHS was the most prevalent cardiac phenotype (4/7) in cases with a KMT2D mutation in this cohort. An additional six (9.1%) cases were found to have potentially deleterious variants in candidate genes.

CONCLUSIONS

Single-gene defects contribute substantially to the genetic etiology of fetal LSLs. KMT2D mutations accounted for approximately 10% of LSLs in our fetal cohort. WES has the potential to provide genetic diagnoses in fetuses with LSLs without aneuploidy or pCNVs. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Management of adults with coarctation of aorta

Coarctation of the aorta (CoA) is a relatively common congenital cardiac defect often causing few symptoms and therefore can be challenging to diagnose. The hallmark finding on physical examination is upper extremity hypertension, and for this reason, CoA should be considered in any young hypertensive patient, justifying measurement of lower extremity blood pressure at least once in these individuals. The presence of a significant pressure gradient between the arms and legs is highly suggestive of the diagnosis. Early diagnosis and treatment are important as long-term data consistently demonstrate that patients with CoA have a reduced life expectancy and increased risk of cardiovascular complications. Surgical repair has traditionally been the mainstay of therapy for correction, although advances in endovascular technology with covered stents or stent grafts permit nonsurgical approaches for the management of older children and adults with native CoA and complications. Persistent hypertension and vascular dysfunction can lead to an increased risk of coronary disease, which, remains the greatest cause of long-term mortality. Thus, blood pressure control and periodic reassessment with transthoracic echocardiography and three-dimensional imaging (computed tomography or cardiac magnetic resonance) for should be performed regularly as cardiovascular complications may occur decades after the intervention.

Environmental and Socioeconomic Factors Influence the Live-Born Incidence of Congenital Heart Disease: A Population-Based Study in California

BACKGROUND

The development of congenital heart disease (CHD) is multifactorial with genetic and environmental influences. We sought to determine the relationship between socioeconomic and environmental factors with the incidence of CHD among live‐born infants in California and to determine whether maternal comorbidities are in the causal pathway.

METHODS AND RESULTS

This was a population‐based cohort study in California (2007–2012). The primary outcome was having significant CHD. Predictors included socioeconomic status and environmental exposure to pollutants determined by U.S. Census data. A social deprivation index and environmental exposure index was assigned based on neighborhood socioeconomic variables, categorized into 4 quartiles. Quartile 1 was the best with the least exposure to pollutants and social deprivation, and quartile 4 was the worst. Multivariate logistic regression and mediation analyses were performed. Among 2 419 651 live‐born infants, the incidence of CHD was 3.2 per 1000 live births. The incidence of CHD was significantly higher among those in quartile 4 compared with quartile 1 (social deprivation index: 0.35% versus 0.29%; odds ratio [OR], 1.31; 95% CI, 1.21–1.41; environmental exposure index: 0.35% versus 0.29%; OR, 1.23; 95% CI, 1.15–1.31) after adjusting for maternal race/ethnicity and age and accounting for the relationship between the 2 primary predictors. Maternal comorbidities explained 13% (95% CI, 10%–20%) of the relationship between social deprivation index and environmental exposure index with the incidence of CHD.

CONCLUSIONS

Increased social deprivation and exposure to environmental pollutants are associated with the incidence of live‐born CHD in California. Maternal comorbidities explain some, but not all, of this relationship. These findings identify targets for social policy initiatives to minimize health disparities.

Transplantation-free survival after Norwood surgery for hypoplastic left heart syndrome with aortic atresia: A Swedish national cohort study

BACKGROUND

Norwood surgery has been available in Sweden since 1993. In this national cohort study, we analysed transplantation-free survival after Norwood surgery for hypoplastic left heart syndrome with aortic atresia.

METHODS

Patients were identified from the complete national cohort of live-born with hypoplastic left heart syndrome/aortic atresia 1993-2010. Analysis of survival after surgery was performed using Cox proportional hazards models for the total cohort and for birth period and gender separately. Thirty-day mortality and inter-stage mortality were analysed. Patients were followed until September 2016.

RESULTS

The 1993-2010 cohort consisted of 208 live-born infants. Norwood surgery was performed in 121/208 (58%). The overall transplantation-free survival was 61/121 (50%). The survival was higher in the late period (10-year survival 63%) than in the early period (10-year survival 40%) (p = 0.010) and lower for female (10-year survival 34%) than for male patients (10-year survival 59%) (p = 0.002). Inter-stage mortality between stages I and II decreased from 23 to 8% (p = 0.008). For male patients, low birthweight in relation to gestational age was a factor associated with poor outcome.

CONCLUSION

The survival after Norwood surgery for hypoplastic left heart syndrome/aortic atresia improved by era of surgery, mainly explained by improved survival between stages I and II. Female gender was a significant risk factor for death or transplantation. For male patients, there was an increased risk of death when birthweight was lower than expected in relation to gestational age.

Changing Epidemiology of Hypoplastic Left Heart Syndrome: Results of a National Swedish Cohort Study

Background Norwood surgery provides a palliative surgical option for hypoplastic left heart syndrome and has been available in Sweden since 1993. The practice of prenatal ultrasound screening was gradually implemented in the same era, resulting in an increased prenatal detection rate. Our primary aims were to study changes in the incidence of live births, prenatal detection rate, and the termination of pregnancies over time. The secondary aims were to study the proportion of live-borns undergoing surgery and to identify factors that influenced whether surgery was or was not performed. Methods and Results Neonates with hypoplastic left heart syndrome with aortic atresia born 1990-2010 were identified through national databases, surgical files, and medical records. The fetal incidence was estimated from the period when prenatal screening was rudimentary. The study period was divided into the presurgical, early surgical, and late surgical periods. The incidence was calculated as the overall yearly incidence for each time period and sex separately. Factors influencing whether surgery was performed were analyzed using Cox-logistic regression. The incidence at live birth decreased from 15.4 to 8.4 per 100 000. The prenatal detection rate increased from 27% to 63%, and terminations increased from 19% to 56%. The odds of having surgery was higher in the late period and higher in the group with prenatal diagnosis. Conclusions We observed a decrease in incidence of live-borns with hypoplastic left heart syndrome aortic atresia. There was in increase in prenatal detection rate and an increase in termination of pregnancy. The proportion of live-borns who underwent surgery increased between time periods.

De novo and recessive forms of congenital heart disease have distinct genetic and phenotypic landscapes

The genetic architecture of sporadic congenital heart disease (CHD) is characterized by enrichment in damaging de novo variants in chromatin-modifying genes. To test the hypothesis that gene pathways contributing to de novo forms of CHD are distinct from those for recessive forms, we analyze 2391 whole-exome trios from the Pediatric Cardiac Genomics Consortium. We deploy a permutation-based gene-burden analysis to identify damaging recessive and compound heterozygous genotypes and disease genes, controlling for confounding effects, such as background mutation rate and ancestry. Cilia-related genes are significantly enriched for damaging rare recessive genotypes, but comparatively depleted for de novo variants. The opposite trend is observed for chromatin-modifying genes. Other cardiac developmental gene classes have less stratification by mode of inheritance than cilia and chromatin-modifying gene classes. Our analyses reveal dominant and recessive CHD are associated with distinct gene functions, with cilia-related genes providing a reservoir of rare segregating variation leading to CHD.

Large whole-exome sequencing studies have suggested that the genetic architecture of syndromic congenital heart disease (CHD) is different from sporadic forms. Here, Watkins et al. estimate the relative contribution of damaging recessive and de novo genotypes to CHD in 2391 trios and find them to be associated with different gene functions.

Congenital left heart obstruction: ethnic variation in incidence and infant survival

OBJECTIVE

To investigate the relationship between ethnicity and health outcomes among fetuses and infants with congenital left heart obstruction (LHO).

DESIGN

A retrospective population-based review was conducted of fetuses and infants with LHO including all terminations, stillbirths and live births from 20 weeks' gestation in New Zealand over a 9-year period. Disease incidence and mortality were analysed by ethnicity and by disease type: hypoplastic left heart syndrome (HLHS), aortic arch obstruction (AAO), and aortic valve and supravalvular anomalies (AVSA).

RESULTS

Critical LHO was diagnosed in 243 fetuses and newborns. There were 125 with HLHS, 112 with AAO and 6 with isolated AVSA. The incidence of LHO was significantly higher among Europeans (0.59 per 1000) compared with Māori (0.31 per 1000; p<0.001) and Pacific peoples (0.27 per 1000; p=0.002). Terminations were uncommon among Māori and Pacific peoples. Total case fatality was, however, lower in Europeans compared with other ethnicities (42% vs 63%; p=0.002) due to a higher surgical intervention rate and better infant survival. The perinatal and infant mortality rate was 82% for HLHS, 15% for AAO and 2% for AVSA.

CONCLUSION

HLHS carries a high perinatal and infant mortality risk. There are ethnic differences in the incidence of and mortality from congenital LHO with differences in mortality rate suggesting inequities may exist in the perinatal management pathway.

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.

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.

Utilization of Whole Exome Sequencing to Identify Causative Mutations in Familial Congenital Heart Disease

BACKGROUND

Congenital heart disease (CHD) is the most common type of birth defect with family- and population-based studies supporting a strong genetic cause for CHD. The goal of this study was to determine whether a whole exome sequencing (WES) approach could identify pathogenic-segregating variants in multiplex CHD families.

METHODS AND RESULTS

WES was performed on 9 kindreds with familial CHD, 4 with atrial septal defects, 2 with patent ductus arteriosus, 2 with tetralogy of Fallot, and 1 with pulmonary valve dysplasia. Rare variants (<1% minor allele frequency) that segregated with disease were identified by WES, and variants in 69 CHD candidate genes were further analyzed. These selected variants were subjected to in silico analysis to predict pathogenicity and resulted in the discovery of likely pathogenic mutations in 3 of 9 (33%) families. A GATA4 mutation in the transactivation domain, p.G115W, was identified in familial atrial septal defects and demonstrated decreased transactivation ability in vitro. A p.I263V mutation in TLL1 was identified in an atrial septal defects kindred and is predicted to affect the enzymatic functionality of TLL1. A disease-segregating splice donor site mutation in MYH11 (c.4599+1delG) was identified in familial patent ductus arteriosus and found to disrupt normal splicing of MYH11 mRNA in the affected individual.

CONCLUSIONS

Our findings demonstrate the clinical utility of WES to identify causative mutations in familial CHD and demonstrate the successful use of a CHD candidate gene list to allow for a more streamlined approach enabling rapid prioritization and identification of likely pathogenic variants from large WES data sets.

CLINICAL TRIAL REGISTRATION

URL: https://clinicaltrials.gov; Unique Identifier: NCT0112048.

Genome-Wide DNA Methylation Analysis and Epigenetic Variations Associated with Congenital Aortic Valve Stenosis (AVS)

Congenital heart defect (CHD) is the most common cause of death from congenital anomaly. Among several candidate epigenetic mechanisms, DNA methylation may play an important role in the etiology of CHDs. We conducted a genome-wide DNA methylation analysis using an Illumina Infinium 450k human methylation assay in a cohort of 24 newborns who had aortic valve stenosis (AVS), with gestational-age matched controls. The study identified significantly-altered CpG methylation at 59 sites in 52 genes in AVS subjects as compared to controls (either hypermethylated or demethylated). Gene Ontology analysis identified biological processes and functions for these genes including positive regulation of receptor-mediated endocytosis. Consistent with prior clinical data, the molecular function categories as determined using DAVID identified low-density lipoprotein receptor binding, lipoprotein receptor binding and identical protein binding to be over-represented in the AVS group. A significant epigenetic change in the APOA5 and PCSK9 genes known to be involved in AVS was also observed. A large number CpG methylation sites individually demonstrated good to excellent diagnostic accuracy for the prediction of AVS status, thus raising possibility of molecular screening markers for this disorder. Using epigenetic analysis we were able to identify genes significantly involved in the pathogenesis of AVS.

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.

A Systematic Review on the Cost-Effectiveness of Genetic and Electrocardiogram Testing for Long QT Syndrome in Infants and Young Adults

BACKGROUND

Recent improvements in the identification of the genetic basis of long QT syndrome (LQTS) have led to significant changes in the diagnosis and management of this life-threatening condition. Genetic and electrocardiogram (ECG) tests are the most relevant examples among testing strategies for LQTS, yet their cost-effectiveness remains controversial.

OBJECTIVE

The aim of this work was to review the available evidence on the cost-effectiveness of genetic and ECG testing strategies for the diagnosis of LQTS.

METHODS

We performed a systematic review of the literature on the cost-effectiveness of genetic and ECG screening strategies for the early detection of LQTS using MEDLINE, EMBASE, and CRD databases between 2000 and 2013. A weighted version of Drummond checklist was instrumental in further assessing the quality of the included studies.

RESULTS

We identified four eligible articles. Among them, genetic testing in the early detection of LQTS was cost-effective compared with no testing in symptomatic cases and not cost-effective when compared with watchful waiting in asymptomatic first-degree relatives of patients with established LQTS although it reached cost-effectiveness in higher risk subgroups, whereas ECG testing in neonates was highly cost-effective when compared with any screening strategy.

CONCLUSIONS

LQTS profiling and patients' stratification have the potential to improve the disease management. Because of the limited current knowledge in this field, the present review recommends to perform further cost-effectiveness evaluations of the genetic and ECG screening alternatives, especially within European health care systems, which are still not available in the literature on genetic testing.

Maternal socioeconomic status and the risk of congenital heart defects in offspring: a meta-analysis of 33 studies

Background

We conducted this meta-analysis to address the open question of a possible association between maternal socioeconomic status and congenital heart defects (CHDs).

Methods

We searched MEDLINE and EMBASE from their inception to January 1, 2014 for case-control and cohort studies that assessed the association between maternal socioeconomic status and the risk of CHDs. Study-specific relative risk estimates were polled according to random-effect or fixed-effect models.

Results

From 3343 references, a total of 31 case-control studies and 2 cohort studies were enrolled in this meta-analysis, including more than 50,000 cases. We observed that maternal educational attainment, family income and maternal occupation were negatively associated with an 11% (pooled RR = 1.11, 95% CI: 1.03, 1.21), 5% (pooled RR = 1.05, 95% CI: 1.01, 1.09) and 51% (pooled RR = 1.51, 95% CI: 1.02, 2.24) increased risk of CHDs, respectively. In a subgroup analysis by geographic region, the results were inconsistent for the European region (RR = 1.29, 95% CI: 0.99–1.69) and USA/Canada region (RR = 1.06, 95% CI: 0.97, 1.16) in maternal educational attainment.

Conclusion

In summary, this meta-analysis suggests that a lower degree of maternal socioeconomic status is modestly associated with an increased risk of CHDs. However, further investigations are needed to confirm the association.

The association between race/ethnicity and major birth defects in the United States, 1999-2007

OBJECTIVES

We investigated the relationship between race/ethnicity and 27 major birth defects.

METHODS

We pooled data from 12 population-based birth defects surveillance systems in the United States that included 13.5 million live births (1 of 3 of US births) from 1999 to 2007. Using Poisson regression, we calculated prevalence estimates for each birth defect and 13 racial/ethnic groupings, along with crude and adjusted prevalence ratios (aPRs). Non-Hispanic Whites served as the referent group.

RESULTS

American Indians/Alaska Natives had a significantly higher and 50% or greater prevalence for 7 conditions (aPR = 3.97; 95% confidence interval [CI] = 2.89, 5.44 for anotia or microtia); aPRs of 1.5 to 2.1 for cleft lip, trisomy 18, and encephalocele, and lower, upper, and any limb deficiency). Cubans and Asians, especially Chinese and Asian Indians, had either significantly lower or similar prevalences of these defects compared with non-Hispanic Whites, with the exception of anotia or microtia among Chinese (aPR = 2.08; 95% CI = 1.30, 3.33) and Filipinos (aPR = 1.90; 95% CI = 1.10, 3.30) and tetralogy of Fallot among Vietnamese (aPR = 1.60; 95% CI = 1.11, 2.32).

CONCLUSIONS

This is the largest population-based study to our knowledge to systematically examine the prevalence of a range of major birth defects across many racial/ethnic groups, including Asian and Hispanic subgroups. The relatively high prevalence of birth defects in American Indians/Alaska Natives warrants further attention.

Quantification of congenital aortic valve stenosis in pediatric patients: comparison between cardiac magnetic resonance imaging and transthoracic echocardiography

Previous studies showed the reliability of cardiac magnetic resonance imaging (cMRI) in the quantification of aortic valve stenosis in adults. The aim of this retrospective study was to assess the ability of cMRI in the quantification of congenital aortic valve stenosis (CAS) in children. Nineteen patients (mean age 14.0 ± 3.2 years, 15 boys and 4 girls) with CAS were imaged by cMRI and transthoracic echocardiography (TTE). cMRI was performed on a 1.5-Tesla MR scanner (Magnetom Avanto; Siemens Healthcare, Erlangen, Germany) using cine steady-state free precession sequences for the assessment of the aortic valve area (AVA) by MR planimetry and left-ventricular function. Phase-contrast measurement was used in cMRI to assess peak flow velocity above the aortic valve. A positive correlation was found between maximum systolic pressure gradient (MPG) as assessed by cMRI and TTE (28.9 ± 21.2 vs. 41.3 ± 22.7 mmHg, r = 0.84, p = 0.001) with a mean underestimation of 12.4 mmHg by cMRI. Only a weak correlation could be observed between AVA by cMRI and MPG at the aortic valve by TTE (r = -0.50, p = 0.029) and cMRI (r = -0.27, p = 0.40). Furthermore, a positive correlation between myocardial mass (cMRI) and MPG (TTE, r = 0.57, p = 0.01), but not between myocardial mass (cMRI) and AVA (cMRI, r = 0.07, p = 0.77), was found. The assessment of MPG by cMRI in patients with CAS is feasible with a trend toward underestimatation compared with TTE. Moreover, MPG seems to be a more accurate parameter than AVA regarding the prediction of myocardial hypertrophy.

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.

Ethnical variations in the incidence of congenital heart defects in gorgan, northern iran: a single-center study

Background : Congenital heart disease (CHD) is the most common congenital anomaly in newborns. This study was performed to determine the live birth incidence of CHD by ethnicity and sex in Gorgan, Northern Iran.

METHODS

In this longitudinal, hospital-based study, 18162 live births in Dezyani Hospital in Gorgan, North of Iran, were screened for CHD, from 2007 through 2009. Clinical examination, echocardiography, color Doppler, and cardio catheterization were used as diagnostic tools. Sex, ethnicity, and type of CHD for each case were recorded in a pre-designed questionnaire. Results : The incidence rates of CHD in the native Fars, Sistani, and Turkmen subjects were 5.73 (95%CI: 4.53-7.15), 12.27 (95%CI: 8.74-16.73), and 15.93 (95%CI: 10.00-24.02) per 1000 live births, respectively. The Turkmen to native Fars and Sistani to native Fars relative risk for congenital CHD malformations was 2.77 (95%CI: 1.73-4.44; p value < 0.001) and 1.29 (95%CI: 0.77-2.18; p value < 0.323), respectively. While atrial septal defect was the most common lesion in the native Fars subjects (2.14 per 1000 [95%CI: 1.42-3.06]) and in the Sistani subjects (2.84 per 1000 [95%CI: 1.29-5.36]), in the Turkmen subjects, ventricular septal defect (4.36 per 1000 [95%CI: 1.59-9.43]), followed by atrial septal defect, was the most frequent lesion. Conclusion : This study showed that the incidence and pattern of CHD among live births in Gorgan, North of Iran, varied according to ethnicity. The risk of CHD was higher in the Turkmen and Sistani groups than in the Fars population.

Risk factors in the origin of congenital left-ventricular outflow-tract obstruction defects of the heart: a population-based case-control study

The aim of our project was to study possible etiological factors in the origin of congenital heart defects (CHDs) because in the majority of patients the underlying causes are unclear. Cases with different CHD entities as homogeneously as possible were planned for evaluation in the population-based large data set of the Hungarian Case Control Surveillance of Congenital Abnormalities. Dead or surgically corrected 302 live-born cases with different types of left-ventricular outflow tract obstructive defects (LVOT, i.e., valvular aortic stenosis 76, hypoplastic left heart syndrome 76, coarctation of the aorta 113, and other congenital anomalies of aorta 32) were compared with 469 matched controls, 38,151 controls without any defects, and 20,750 malformed controls with other isolated defects. Medically recorded pregnancy complications and chronic diseases were evaluated based on prenatal maternity logbooks, whereas acute diseases, drug treatments, and folic acid/multivitamin supplementation were analyzed both on the basis of retrospective maternal information and medical records. The results of the study showed the role of maternal diabetes in the origin of LVOT in general, while panic disorder was associated with a higher risk of hypoplastic left heart syndrome and ampicillin treatment with a higher risk of coarctation of the aorta (COA). High doses of folic acid had a protective effect regarding the manifestation of LVOT, particularly COA. In conclusion, only a minor portion of causes was shown in our study; thus, further studies are needed to understand better the underlying causal factors in the origin of LVOT.

Folic acid fortification and the birth prevalence of congenital heart defect cases in Alberta, Canada

BACKGROUND

Congenital heart defects (CHDs) are the most common type of congenital anomaly. The precise etiology is unknown and the development of successful primary prevention strategies is challenging. Folic acid may have a protective role; however published results have been inconsistent. This study examines the impact of mandatory folic acid fortification (FAF) on the prevalence of CHDs.

METHODS

CHD cases were ascertained using the Alberta Congenital Anomalies Surveillance System, Pediatric Cardiology Clinics, Pathology, and hospital records. The birth prevalence and odds ratios (OR) of isolated CHD cases (i.e., without noncardiac anomalies) were calculated comparing pre-FAF (1995-1997) with post-FAF (1999-2002).

RESULTS

The prevalence of isolated CHD cases remained relatively unchanged when pre-FAF (9.34, 95% confidence interval [CI] 8.79-9.92) was compared with post-FAF (9.41, 95% CI, 8.93-9.91). Left ventricular outflow tract obstruction (LVOTO) decreased post-FAF (OR, 0.76; 95% CI, 0.61-0.94). Coarctation of the aorta contributed to this decline (OR, 0.55; 95% CI, 0.32-0.92). Atrial septal defect (ASD) (OR, 1.42; 95% CI, 1.13-1.80) and ASD with ventricular septal defect (OR, 1.52; 95% CI, 1.10-2.10) increased post-FAF. The remaining types of CHDs were unchanged.

CONCLUSION

FAF alone does not have an impact on the prevalence of CHDs as a group and the majority of selected types of CHDs in Alberta. The decrease in LVOTO, particularly coarctation of the aorta, may be due to FAF or other environmental factors. The increase in ASD and ASD with ventricular septal defect may reflect an increase in diagnosis and ascertainment.

The prevalence of 16p12.1 microdeletion in patients with left-sided cardiac lesions

SETTING

Left-sided cardiac lesions have a birth prevalence of approximately 1 in 1000 and have been shown to be heritable in pedigree studies. A large microdeletion at 16p12.1 is associated with childhood developmental delay, and initial studies describing this deletion identified left-sided lesions as an enriched phenotype compared with a control population.

OBJECTIVE

The aim of this study is to determine whether patients with left-sided cardiac lesions have an increased frequency of 16p12.1 microdeletions as compared with control populations.

DESIGN

A cohort of 262 probands with left-sided lesions, including 53 with isolated aortic stenosis/bicuspid aortic valve, 83 with coarctation of the aorta with or without aortic stenosis/bicuspid aortic valve, and 126 with hypoplastic left heart syndrome were assessed for copy number variation at 16p12.1. The control cohort included 595 patients with conotruncal defects as a cardiac control and 971 healthy children.

RESULTS

We detected one patient in the left-sided lesion cohort with a large duplication partially overlapping the reported 16p12.1 microdeletion, along with one patient each in the conotruncal and control cohorts with a deletion in the same region. None of these patients had dysmorphic features, extracardiac malformations, or developmental delay.

CONCLUSION

In our cohort, structural variation at 16p12.1 was not identified with increased frequency in patients with left-sided lesions as compared with controls.

Cardiac teratogenicity in mouse maternal phenylketonuria: defining phenotype parameters and genetic background influences

Maternal phenylketonuria (MPKU) is a syndrome including cardiovascular malformations (CVMs), microcephaly, intellectual impairment, and small size for gestational age, caused by in-utero exposure to elevated serum phenylalanine (Phe) due to PKU in the mother. It is becoming a public health concern as more women with PKU reach child bearing age. Although a mouse model of PKU, BTBR Pah(enu2), has been available for 20 years, it has not been well utilized for studying MPKU. We used this model to delineate critical parameters in Phe cardiovascular teratogenicity and study the effect of genetic background. Dosing and timing experiments were performed with the BTBR Pah(enu2) mouse. A dose response curve was noted, with CVM rates at maternal serum Phe levels <360 μM (control), 360-600 μM (low), 600-900 μM (mid), and >900 μM (high) of 11.86%, 16.67%, 30.86%, and 46.67% respectively. A variety of CVMs were noted on the BTBR background, including double outlet right ventricle (DORV), aortic arch artery (AAA) abnormalities, and ventricular septal defects (VSDs). Timed exposure experiments identified a teratogenic window from embryonic day 8.5-13.5, with higher rates of conotruncal and valve defects occurring in early exposure time and persistent truncus arteriosus (PTA) and aortic arch branching abnormalities occurring with late exposure. Compared to the BTBR strain, N10+ Pah(enu2) congenics on the C3H/HeJ background had higher rates of CVMs in general and propensity to left ventricular outflow tract (LVOT) malformations, while the C57B/L6 background had similar CVM rates but predominately AAA abnormalities. We have delineated key parameters of Phe cardiovascular teratogenicity, demonstrated the utility of this MPKU model on different mouse strains, and shown how genetic background profoundly affects the phenotype.

Bicuspid aortic valve and thoracic aortic aneurysm: three patient populations, two disease phenotypes, and one shared genotype

Bicuspid aortic valve (BAV) and thoracic aortic aneurysm (TAA) are two discrete cardiovascular phenotypes characterized by latent progressive disease states. There is a clear association between BAV and TAA; however the nature and extent of this relationship is unclear. There are both distinct and overlapping developmental pathways that have been established to contribute to the formation of the aortic valve and the aortic root, and the mature anatomy of these different tissue types is intimately intertwined. Likewise, human genetics studies have established apparently separate and common contributions to these clinical phenotypes, suggesting complex inheritance and a shared genetic basis and translating 3 patient populations, namely, BAV, TAA, or both, into a common but diverse etiology. A better understanding of the BAV-TAA association will provide an opportunity to leverage molecular information to modify clinical care through more sophisticated diagnostic testing, improved counseling, and ultimately new pharmacologic therapies.

Aortic valve disease and treatment: the need for naturally engineered solutions

The aortic valve regulates unidirectional flow of oxygenated blood to the myocardium and arterial system. The natural anatomical geometry and microstructural complexity ensures biomechanically and hemodynamically efficient function. The compliant cusps are populated with unique cell phenotypes that continually remodel tissue for long-term durability within an extremely demanding mechanical environment. Alteration from normal valve homeostasis arises from genetic and microenvironmental (mechanical) sources, which lead to congenital and/or premature structural degeneration. Aortic valve stenosis pathobiology shares some features of atherosclerosis, but its final calcification endpoint is distinct. Despite its broad and significant clinical significance, very little is known about the mechanisms of normal valve mechanobiology and mechanisms of disease. This is reflected in the paucity of predictive diagnostic tools, early stage interventional strategies, and stagnation in regenerative medicine innovation. Tissue engineering has unique potential for aortic valve disease therapy, but overcoming current design pitfalls will require even more multidisciplinary effort. This review summarizes the latest advancements in aortic valve research and highlights important future directions.

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.

Seasonality of hypoplastic left heart syndrome in the United States: a 10-year time-series analysis

OBJECTIVE

Hypoplastic left heart syndrome is a major congenital heart defect and is associated with significant morbidity and mortality. Its etiology remains unknown although genetic studies imply complex inheritance. Anecdotal reports of cluster presentations suggest the possible involvement of an environmental component, although previous epidemiologic studies have been of limited scope. The objective of this study was to examine seasonal and temporal patterns of hypoplastic left heart syndrome births compared with other left-sided heart defects in the United States.

METHODS

We conducted a retrospective analysis of the Pediatric Health Information System inpatient database from pediatric hospitals across the country from 1996 to 2006. Population and index case patterns were analyzed for each diagnostic category. An epidemiologic survey was performed through time-series analyses using Fisher's Kappa test and the Bartlett Kolmogorov-Smirnov test. The existence and strength of seasonality for the left-sided heart defects was quantified by the autoregression R2.

RESULTS

A seasonal occurrence was found in hypoplastic left heart syndrome but not other left-sided heart diseases. Significant seasonal differences occurred each year, with peaks in summer months and troughs in winter months. The seasonality inversely correlated with the incidence of chromosomal and extracardiac anomalies; such anomalies were highest in interrupted aortic arch, which had a random pattern of presentation.

CONCLUSIONS

There is a significant seasonal pattern in the presentation of hypoplastic left heart syndrome, with preponderance in summer months, in contrast to the random pattern in other left-sided heart diseases. Further studies are warranted to identify the influence of potential environmental factor(s) in hypoplastic left heart syndrome, as seen in diseases with seasonal patterns.

The severe end of the spectrum: Hypoplastic left heart in Potocki-Lupski syndrome

Potocki-Lupski syndrome (PTLS) is a recently described microduplication syndrome associated with duplication 17p11.2, including the RAI1 gene. Features of PTLS include hypotonia, feeding difficulties, failure to thrive, developmental delay and behavioral abnormalities including autistic spectrum disorder, anxiety, and inattention. Cardiovascular anomalies were not recognized as a feature of duplication 17p11.2 until 2007 when noted in over 50% of a clinically characterized cohort. We report a patient with hypoplastic left heart syndrome whose diagnosis of PTLS was delayed until a genetic evaluation at age 4 years because of severe expressive language impairment. We suggest that array comparative genomic hybridization be performed in infants with severe congenital heart defects.

NOTCH1 missense alleles associated with left ventricular outflow tract defects exhibit impaired receptor processing and defective EMT

Notch signaling is essential for proper cardiac development. We recently identified missense variants in the NOTCH1 receptor in patients with diverse left ventricular outflow tract (LVOT) malformations (NOTCH1(G661S) and NOTCH1(A683T)) that reduce ligand-induced Notch signaling. Here, we examine the molecular mechanisms that contribute to reduced signaling and perturbed development. We find that NOTCH1(A683T) exhibits reduced S1 cleavage due to impaired trafficking through the endoplasmic reticulum (ER). This observation is consistent with improper localization of the variant receptor to the ER and decreased presentation at the cell surface. In contrast, the nearby mutation NOTCH1(G661S) exhibits reduced cell-surface presentation in the absence of overt folding or trafficking defects. To examine the implications of these variants in disease pathogenesis, we investigated their effect on epithelial-to-mesenchymal transition (EMT), a critical process for development of the outflow tract. We find that these LVOT-associated NOTCH1 alleles can contribute to defective EMT in endothelial cell lines through impaired induction of Snail and Hes family members. These data represent the first description of a molecular mechanism underlying NOTCH1 mutations in individuals with LVOT malformations, and have important implications regarding the functional contribution of these alleles to a complex set of developmental defects.

Variation in the prevalence of congenital heart defects by maternal race/ethnicity and infant sex

OBJECTIVE

To determine the prevalence of major congenital heart defects (CHD) by ethnicity and sex.

STUDY DESIGN

Data from the Florida Birth Defects Registry was used to conduct a retrospective cohort study with 8029 singleton infants with 11 CHDs born 1998-2003 to resident non-Hispanic (NH) white, NH-black, and Hispanic women aged 15 to 49. Defect-specific prevalence rates, ratios, and 95% confidence intervals were calculated. Poisson regression was used to calculate adjusted ethnic-specific rate ratios (RR) for each CHD. Statistical significance was P < .0001.

RESULTS

Compared with NH-whites, NH-black males had significantly increased rates of pulmonary valve atresia/stenosis (RR = 1.66) but lower prevalence of aortic valve atresia/stenosis (RR = 0.33) and ventricular septal defect (VSD; RR = 0.78). Hispanic males had lower rates of aortic valve atresia/stenosis (RR = 0.28), coarctation of the aorta (RR = 0.61) and VSD (RR = 0.79). NH-black females had statistically significantly lower rates of VSD (RR = 0.75), and Hispanic females had lower rates of tetralogy of Fallot (RR = 0.54), VSD (RR = 0.84) and atrioventricular septal defects (RR = 0.53) compared with NH-whites.

CONCLUSIONS

We found differences in ethnic susceptibilities to CHD by sex, but the cause remains unclear.

Coarctation of the aorta: a case presentation

Coarctation is a constriction or narrowing of the aorta and presents most commonly within the first two weeks of life. This article reviews a case study of an infant diagnosed with coarctation of the aorta on day 8 of life. It includes an overview of the etiology, clinical presentation, and management plus an account of the infant's transport to a regional pediatric intensive care unit (PICU).

Linkage analysis of left ventricular outflow tract malformations (aortic valve stenosis, coarctation of the aorta, and hypoplastic left heart syndrome)

The left ventricular outflow tract (LVOT) malformations aortic valve stenosis (AVS), coarctation of the aorta (CoA), and hypoplastic left heart syndrome (HLHS) are significant causes of infant mortality. These three malformations are thought to share developmental pathogenetic mechanisms. A strong genetic component has been demonstrated earlier, but the underlying genetic etiologies are unknown. Our objective was to identify genetic susceptibility loci for the broad phenotype of LVOT malformations. We genotyped 411 microsatellites spaced at an average of 10 cM in 43 families constituting 289 individuals, with an additional 5 cM spaced markers for fine mapping. A non-parametric linkage (NPL) analysis of the combined LVOT malformations gave three suggestive linkage peaks on chromosomes 16p12 (NPL score (NPLS)=2.52), 2p23 (NPLS=2.41), and 10q21 (NPLS=2.14). Individually, suggestive peaks for AVS families occurred on chromosomes 16p12 (NPLS=2.64), 7q36 (NPLS=2.31), and 2p25 (NPLS=2.14); and for CoA families on chromosome 1q24 (NPLS=2.61), 6p23 (NPLS=2.29), 7p14 (NPLS=2.27), 10q11 (NPLS=1.98), and 2p15 (NPLS=2.02). Significant NPLS in HLHS families were noted for chromosome 2p15 (NPLS=3.23), with additional suggestive peaks on 19q13 (NPLS=2.16) and 10q21 (NPLS=2.07). Overlapping linkage signals on 10q11 (AVS and CoA) and 16p12 (AVS, CoA, and HLHS) led to higher NPL scores when all malformations were analyzed together. In conclusion, we report suggestive evidence for linkage to chromosomes 2p23, 10q21, and 16p12 for the LVOT malformations of AVS, CoA, and HLHS individually and in a combined analysis, with a significant peak on 2p15 for HLHS. Overlapping linkage peaks provide evidence for a common genetic etiology.

NOTCH1 mutations in individuals with left ventricular outflow tract malformations reduce ligand-induced signaling

Congenital aortic valve stenosis (AVS), coarctation of the aorta (COA) and hypoplastic left heart syndrome (HLHS) are congenital cardiovascular malformations that all involve the left ventricular outflow tract (LVOT). They are presumably caused by a similar developmental mechanism involving the developing endothelium. The exact etiology for most LVOT malformations is unknown, but a strong genetic component has been established. We demonstrate here that mutations in the gene NOTCH1, coding for a receptor in a developmentally important signaling pathway, are found across the spectrum of LVOT defects. We identify two specific mutations that reduce ligand (JAGGED1) induced NOTCH1 signaling. One of these mutations perturbs the S1 cleavage of the receptor in the Golgi. These findings suggest that the levels of NOTCH1 signaling are tightly regulated during cardiovascular development, and that relatively minor alterations may promote LVOT defects. These results also establish for the first time that AVS, COA and HLHS can share a common pathogenetic mechanism at the molecular level, explaining observations of these defects co-occurring within families.