Epidemiology of cardiovascular malformations: prevalence and risk factors

Nr2f1a maintains atrial nkx2.5 expression to repress pacemaker identity within venous atrial cardiomyocytes of zebrafish

Maintenance of cardiomyocyte identity is vital for normal heart development and function. However, our understanding of cardiomyocyte plasticity remains incomplete. Here, we show that sustained expression of the zebrafish transcription factor Nr2f1a prevents the progressive acquisition of ventricular cardiomyocyte (VC) and pacemaker cardiomyocyte (PC) identities within distinct regions of the atrium. Transcriptomic analysis of flow-sorted atrial cardiomyocytes (ACs) from nr2f1a mutant zebrafish embryos showed increased VC marker gene expression and altered expression of core PC regulatory genes, including decreased expression of nkx2.5, a critical repressor of PC differentiation. At the arterial (outflow) pole of the atrium in nr2f1a mutants, cardiomyocytes resolve to VC identity within the expanded atrioventricular canal. However, at the venous (inflow) pole of the atrium, there is a progressive wave of AC transdifferentiation into PCs across the atrium toward the arterial pole. Restoring Nkx2.5 is sufficient to repress PC marker identity in nr2f1a mutant atria and analysis of chromatin accessibility identified an Nr2f1a-dependent nkx2.5 enhancer expressed in the atrial myocardium directly adjacent to PCs. CRISPR/Cas9-mediated deletion of the putative nkx2.5 enhancer leads to a loss of Nkx2.5-expressing ACs and expansion of a PC reporter, supporting that Nr2f1a limits PC differentiation within venous ACs via maintaining nkx2.5 expression. The Nr2f-dependent maintenance of AC identity within discrete atrial compartments may provide insights into the molecular etiology of concurrent structural congenital heart defects and associated arrhythmias.

Double outlet ventricles: review of anatomic and imaging characteristics

Hearts with double outlet ventricles and concordant atrioventricular connections account for about 1%–3% of all cases of congenital heart disease. We review hearts with two ventricles and concordant atrioventricular connections with double outlet right ventricle (DORV), double outlet left ventricle (DOLV) and double outlet both ventricles (DOBV) from the morphological and clinical imaging perspectives. These hearts are a heterogeneous group of congenital cardiac malformations with a wide range of pathophysiologies that require an individualised surgical approach based on a precise understanding of the complex cardiovascular anatomy. Owing to their differing temporal, spatial and contrast resolutions, we propose that multimodality imaging provides optimal characterisation of various intracardiac morphological features of double outlet hearts. This approach aids clinical diagnosis for optimising treatment options across these malformations.

Three-dimensional printing and virtual reconstruction in surgical planning of double-outlet right ventricle repair

Objectives

For more than a decade, 3-dimensional (3D) printing has been identified as an innovative tool for the surgical planning of double-outlet right ventricle (DORV). Nevertheless, lack of evidence concerning its benefits encourages us to identify valuable criteria for future prospective trials.

Methods

We conducted a retrospective study involving 10 patients with DORV operated between 2015 and 2019 in our center. During a preoperative multidisciplinary heart team meeting, we harvested surgical decisions following a 3-increment step process: (1) multimodal imaging; (2) 3D virtual valvular reconstruction (3DVVR); and (3) 3D-printed heart model (3DPHM). The primary outcome was the proportion of predicted surgical strategy following each of the 3 steps, compared with the institutional retrospective surgical strategy. The secondary outcome was the change of surgical strategy through 3D modalities compared with multimodal imaging. The incremental benefit of the 3DVVR and 3DPHM over multimodal imaging was then assessed.

Results

The operative strategy was predicted in 5 cases after multimodal imaging, in 9 cases after 3DVVR, and the 10 cases after 3DPHM. Compared with multimodal imaging, 3DVVR modified the strategy for 4 cases. One case was correctly predicted only after 3DPHM inspection.

Conclusions

3DVVR and 3DPHM improved multimodal imaging in the surgical planning of patients with DORV. 3DVVR allowed a better appreciation of the relationships between great vessels, valves, and ventricular septal defects. 3DPHM offers a realistic preoperative view at patient scale and enhances the evaluation of outflow tract obstruction. Our retrospective study demonstrates benefits of preoperative 3D modalities and supports future prospective trials to assess their impact on postoperative outcomes.

LARP7 Suppresses Endothelial-to-Mesenchymal Transition by Coupling With TRIM28

[Figure: see text].

Folic acid prevents functional and structural heart defects induced by prenatal ethanol exposure

State-of-the-art biophotonic tools captured blood flow and endocardial cushion volumes in tiny beating quail embryo hearts, an accessible model for studying four-chambered heart development. Both hemodynamic flow and endocardial cushion volumes were altered with ethanol exposure but normalized when folic acid was introduced with ethanol. Folic acid supplementation preserved hemodynamic function that is intimately involved in sculpting the heart from the earliest stages of heart development.

Disruptions in the development of feeding for infants with congenital heart disease

Congenital heart disease (CHD) is the most common birth defect for infants born in the United States, with approximately 36,000 affected infants born annually. While mortality rates for children with CHD have significantly declined, there is a growing population of individuals with CHD living into adulthood prompting the need to optimise long-term development and quality of life. For infants with CHD, pre- and post-surgery, there is an increased risk of developmental challenges and feeding difficulties. Feeding challenges carry profound implications for the quality of life for individuals with CHD and their families as they impact short- and long-term neurodevelopment related to growth and nutrition, sensory regulation, and social-emotional bonding with parents and other caregivers. Oral feeding challenges in children with CHD are often the result of medical complications, delayed transition to oral feeding, reduced stamina, oral feeding refusal, developmental delay, and consequences of the overwhelming intensive care unit (ICU) environment. This article aims to characterise the disruptions in feeding development for infants with CHD and describe neurodevelopmental factors that may contribute to short- and long-term oral feeding difficulties.

Atrial and Sinoatrial Node Development in the Zebrafish Heart

Proper development and function of the vertebrate heart is vital for embryonic and postnatal life. Many congenital heart defects in humans are associated with disruption of genes that direct the formation or maintenance of atrial and pacemaker cardiomyocytes at the venous pole of the heart. Zebrafish are an outstanding model for studying vertebrate cardiogenesis, due to the conservation of molecular mechanisms underlying early heart development, external development, and ease of genetic manipulation. Here, we discuss early developmental mechanisms that instruct appropriate formation of the venous pole in zebrafish embryos. We primarily focus on signals that determine atrial chamber size and the specialized pacemaker cells of the sinoatrial node through directing proper specification and differentiation, as well as contemporary insights into the plasticity and maintenance of cardiomyocyte identity in embryonic zebrafish hearts. Finally, we integrate how these insights into zebrafish cardiogenesis can serve as models for human atrial defects and arrhythmias.

Mental Health Disorders in Children With Congenital Heart Disease

BACKGROUND

Data on anxiety, depression, and attention-deficit/hyperactivity disorder (ADHD) are lacking for youth with congenital heart disease (CHD), particularly those with simple CHD. This study aims to characterize these disorders in youth with CHD compared to those without CHD.

METHODS

A comparative cross-sectional study was conducted by using the electronic medical records of a large tertiary care hospital between 2011 and 2016. Inclusion criteria were youth aged 4 to 17 years with >1 hospitalization or emergency department visits. Exclusion criteria were patients with arrhythmias or treatment with clonidine and/or benzodiazepines. The primary predictor variable was CHD type: simple, complex nonsingle ventricle, and complex single ventricle. The primary outcome variable was a diagnosis and/or medication for anxiety and/or depression or ADHD. Data were analyzed by using logistic regression (Stata v15; Stata Corp, College Station, TX).

RESULTS

We identified 118 785 patients, 1164 with CHD. Overall, 18.2% (n = 212) of patients with CHD had a diagnosis or medication for anxiety or depression, compared with 5.2% (n = 6088) of those without CHD. All youth with CHD had significantly higher odds of anxiety and/or depression or ADHD. Children aged 4 to 9 years with simple CHD had ∼5 times higher odds (odds ratio: 5.23; 95% confidence interval: 3.87-7.07) and those with complex single ventricle CHD had ∼7 times higher odds (odds ratio: 7.46; 95% confidence interval: 3.70-15.07) of diagnosis or treatment for anxiety and/or depression. Minority and uninsured youth were significantly less likely to be diagnosed or treated for anxiety and/or depression or ADHD, regardless of disease severity.

CONCLUSIONS

Youth with CHD of all severities have significantly higher odds of anxiety and/or depression and ADHD compared to those without CHD. Screening for these conditions should be considered in all patients with CHD.

Reprogramming Axial Level Identity to Rescue Neural-Crest-Related Congenital Heart Defects

The cardiac neural crest arises in the hindbrain, then migrates to the heart and contributes to critical structures, including the outflow tract septum. Chick cardiac crest ablation results in failure of this septation, phenocopying the human heart defect persistent truncus arteriosus (PTA), which trunk neural crest fails to rescue. Here, we probe the molecular mechanisms underlying the cardiac crest's unique potential. Transcriptional profiling identified cardiac-crest-specific transcription factors, with single-cell RNA sequencing revealing surprising heterogeneity, including an ectomesenchymal subpopulation within the early migrating population. Loss-of-function analyses uncovered a transcriptional subcircuit, comprised of Tgif1, Ets1, and Sox8, critical for cardiac neural crest and heart development. Importantly, ectopic expression of this subcircuit was sufficient to imbue trunk crest with the ability to rescue PTA after cardiac crest ablation. Together, our results reveal a transcriptional program sufficient to confer cardiac potential onto trunk neural crest cells, thus implicating new genes in cardiovascular birth defects.

Mechanisms of heart valve development and disease

The valves of the heart are crucial for ensuring that blood flows in one direction from the heart, through the lungs and back to the rest of the body. Heart valve development is regulated by complex interactions between different cardiac cell types and is subject to blood flow-driven forces. Recent work has begun to elucidate the important roles of developmental pathways, valve cell heterogeneity and hemodynamics in determining the structure and function of developing valves. Furthermore, this work has revealed that many key genetic pathways involved in cardiac valve development are also implicated in diseased valves. Here, we review recent discoveries that have furthered our understanding of the molecular, cellular and mechanosensitive mechanisms of valve development, and highlight new insights into congenital and acquired valve disease.

Impacts of an Interdisciplinary Developmental Follow-Up Program on Neurodevelopment in Congenital Heart Disease: The CINC Study

Objectives: This study investigates the impact of an early systematic interdisciplinary developmental follow-up and individualized intervention program on the neurodevelopment of children with complex congenital heart disease (CHD) who required cardiac surgery. Study Design: We prospectively enrolled 80 children with CHD: 41 were already followed at our neurocardiac developmental follow-up clinic from the age of 4 months, while 39 were born before the establishment of the program and therefore received standard health care. We conducted cognitive, motor, and behavioral assessments at 3 years of age. We used one-way multivariate analyses of variance to compare the neurodevelopmental outcome of both groups. Results: Between-group analyses revealed a distinct neurodevelopmental profile with clinically significant effect size (P < 0.001, partial η² = 0.366). Children followed at our clinic demonstrated better receptive language performances (P = 0.048) and tended to show higher scores on visuo-constructive tasks (P = 0.080). Children who received standard health care exhibited greater performances in working memory tasks (P = 0.032). We found no group differences on global intellectual functioning, gross and fine motor skills, and behaviors. Referral rates for specific remedial services were higher in patients followed at our neurocardiac clinic compared to the historical cohort (P < 0.005). Conclusions: Overall, the impact of the developmental follow-up and individualized intervention program on neurodevelopmental outcomes remains subtle. Nevertheless, results, although limited by several factors, point toward an advantage for the children who took part in the program regarding receptive language skills over children who received standard health care. We hypothesize that group differences may be greater with growing age. Further research involving larger cohorts is needed to clearly assess the effectiveness of neurocardiac developmental follow-up programs at school age.

Say NO to ROS: Their Roles in Embryonic Heart Development and Pathogenesis of Congenital Heart Defects in Maternal Diabetes

Congenital heart defects (CHDs) are the most prevalent and serious birth defect, occurring in 1% of all live births. Pregestational maternal diabetes is a known risk factor for the development of CHDs, elevating the risk in the child by more than four-fold. As the prevalence of diabetes rapidly rises among women of childbearing age, there is a need to investigate the mechanisms and potential preventative strategies for these defects. In experimental animal models of pregestational diabetes induced-CHDs, upwards of 50% of offspring display congenital malformations of the heart, including septal, valvular, and outflow tract defects. Specifically, the imbalance of nitric oxide (NO) and reactive oxygen species (ROS) signaling is a major driver of the development of CHDs in offspring of mice with pregestational diabetes. NO from endothelial nitric oxide synthase (eNOS) is crucial to cardiogenesis, regulating various cellular and molecular processes. In fact, deficiency in eNOS results in CHDs and coronary artery malformation. Embryonic hearts from diabetic dams exhibit eNOS uncoupling and oxidative stress. Maternal treatment with sapropterin, a cofactor of eNOS, and antioxidants such as N-acetylcysteine, vitamin E, and glutathione as well as maternal exercise have been shown to improve eNOS function, reduce oxidative stress, and lower the incidence CHDs in the offspring of mice with pregestational diabetes. This review summarizes recent data on pregestational diabetes-induced CHDs, and offers insights into the important roles of NO and ROS in embryonic heart development and pathogenesis of CHDs in maternal diabetes.

EDUCATIONAL SERIES IN CONGENITAL HEART DISEASE: Tetralogy of Fallot: diagnosis to long-term follow-up

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect, affecting 3 in 10,000 live births. Surgical correction in early childhood is associated with good outcomes, but lifelong follow-up is necessary to identify the long-term sequelae that may occur. This article will cover the diagnosis of TOF in childhood, the objectives of surveillance through adulthood and the value of multi-modality imaging in identifying and guiding timely surgical and percutaneous interventions.

Improving neurodevelopmental outcomes in children with congenital heart disease: protocol for a randomised controlled trial of working memory training

INTRODUCTION

Executive function (EF) impairments are among the most prevalent neurodevelopmental morbidities in youth with congenital heart disease (CHD). To date, no studies have investigated the efficacy of cognitive interventions to improve EF outcomes in children with CHD.

METHODS AND ANALYSIS

This is a single-centre, single-blinded, two-arm randomised controlled trial to test the efficacy of Cogmed Working Memory Training (Cogmed) versus standard of care in children with CHD after open-heart surgery in infancy. Participants will consist of 100 children with CHD aged 7-12 years who underwent open-heart surgery before the age of 12 months. Participants are randomly allocated to either an intervention group including training on the home-based Cogmed intervention for a duration of approximately 5 weeks or a control group who receive the standard of care. We will evaluate the efficacy of Cogmed at post-treatment and 3 months after completion of the intervention. Baseline, post-treatment and 3-month follow-up assessments will include specific measures of EF, cognitive and social functioning, and attention deficit hyperactivity disorder (ADHD) symptoms. The primary outcome of this study is the change in standardised mean score on the List Sorting Working Memory test from the National Institutes of Health Toolbox for the Assessment of Neurological and Behavioral Function. Secondary outcomes include measures of social skills, inhibitory control, cognitive flexibility and behavioural EF as well as ADHD symptoms as measured by the Behavior Rating Inventory of Executive Function, Second Edition, and the Conners Third Edition. The efficacy of the intervention will be evaluated by comparing within-subject differences (baseline to post-treatment, baseline to 3-month follow-up) between the two groups using an intention-to-treat analysis.

ETHICS AND DISSEMINATION

This study has received Institutional Review Board (IRB) approval from Boston's Children's Hospital IRB (P00022440) and the Human Protection Agency from the US Department of Defense.

TRIAL REGISTRATION NUMBER

NCT03023644; Pre-results.

Grief and coping of parents whose child has a constant life-threatening disability, hypoplastic left heart syndrome with reference to the Dual-Process Model

This paper reports on a study that examined the grief and coping of 29 parents whose child has hypoplastic left heart syndrome using the Dual Process Model. The study employed a secondary thematic analysis of interviews at key times of treatment and recovery for the child. After the diagnosis, parents experienced intense loss (LO), but focused upon restoration-orientated tasks (RO) to support their child. Over time, most parents employed a healthy oscillation between LO coping and RO coping, with waves of grief and with some grieving suppressed. There are some specific grief and coping and gender patterns employed by parents.

Patient-specific in vivo right ventricle material parameter estimation for patients with tetralogy of Fallot using MRI-based models with different zero-load diastole and systole morphologies

Patient-specific in vivo ventricle material parameter determination is important for cardiovascular investigations. A new cardiac magnetic image (CMR)-based modeling approach with different zero-load diastole and systole geometries was adopted to estimate right ventricle material parameter values for healthy and patients with Tetralogy of Fallot (TOF) and seeking potential clinical applications. CMR data were obtained from 6 healthy volunteers and 16 TOF patients with consent obtained. CMR-based RV/LV models were constructed using two zero-load geometries (diastole and systole, 2G model). Material parameter values for begin-filling (BF), end-filling (EF), begin-ejection (BE), and end-ejection (EE) were recorded for analyses. Effective Young's moduli (YM) for fiber direction stress-strain curves were calculated for easy comparisons. The mean EE YM value of TOF patients was 78.6% higher than that of the healthy group (HG). The mean end-ejection YM value from worse-outcome TOF group (WG) post pulmonary valve replacement (PVR) surgery was 59.5% higher than that from the better-outcome TOF group (BG). Using begin-filling YM and end-ejection YM as predictors and the classic logistic regression model to different better-outcome group patients from worse-outcome group patients, the areas under Receiver Operating Characteristic (ROC) curves were found to be 0.797 and 0.883 for begin-filling YM and end-ejection YM, respectively. The sensitivity and specificity 0.761 and 0.755 using end-ejection YM as the predictor. This preliminary study suggests that ventricle material stiffness could be a potential parameter to be used to differentiate BG patients from WG patients with further effort and large-scale patient data validations.

Knockout of tnni1b in zebrafish causes defects in atrioventricular valve development via the inhibition of the myocardial wnt signaling pathway

The proper development of atrioventricular (AV) valves is critical for heart morphogenesis and for the formation of the cardiac conduction system. Defects in AV valve development are the most common type of congenital heart defect. Cardiac troponin I ( ctnni), a structural and regulatory protein involved in cardiac muscle contraction, is a subunit of the troponin complex, but the functions and molecular mechanisms of ctnni during early heart development remain unclear. We created a knockout zebrafish model in which troponin I type 1b ( tnni1b) ( Tnni-HC, heart and craniofacial) was deleted using the clustered regularly interspaced short palindromic repeat/clustered regularly interspaced short palindromic repeat-associated protein system. In the homozygous mutant, the embryos showed severe pericardial edema, malformation of the heart tube, reduction of heart rate without contraction and with almost no blood flow, heart cavity congestion, and lack of an endocardial ring or valve leaflet, resulting in 88.8 ± 6.0% lethality at 7 d postfertilization. Deletion of tnni1b caused the abnormal expression of several markers involved in AV valve development, including bmp4, cspg2, has2, notch1b, spp1, and Alcam. Myocardial re-expression of tnni1b in mutants partially rescued the pericardial edema phenotype and AV canal (AVC) developmental defects. We further showed that tnni1b knockout in zebrafish and ctnni knockdown in rat h9c2 myocardial cells inhibited cardiac wnt signaling and that myocardial reactivation of wnt signaling partially rescued the abnormal expression of AVC markers caused by the tnni1b deletion. Taken together, our data suggest that tnni1b plays a vital role in zebrafish AV valve development by regulating the myocardial wnt signaling pathway.-Cai, C., Sang, C., Du, J., Jia, H., Tu, J., Wan, Q., Bao, B., Xie, S., Huang, Y., Li, A., Li, J., Yang, K., Wang, S., Lu, Q. Knockout of tnni1b in zebrafish causes defects in atrioventricular valve development via the inhibition of myocardial wnt signaling pathway.

Risk Factors for Ventricular Septal Defects in Murmansk County, Russia: A Registry-Based Study

Cardiovascular malformations are one of the most common birth defects among newborns and constitute a leading cause of perinatal and infant mortality. Although some risk factors are recognized, the causes of cardiovascular malformations (CVMs) remain largely unknown. In this study, we aim to identify risk factors for ventricular septal defects (VSDs) in Northwest Russia. The study population included singleton births registered in the Murmansk County Birth Registry (MCBR) between 1 January 2006 and 31 December 2011. Infants with a diagnosis of VSD in the MCBR and/or in the Murmansk Regional Congenital Defects Registry (up to two years post-delivery) constituted the study sample. Among the 52,253 infants born during the study period there were 744 cases of septal heart defects (SHDs), which corresponds to a prevalence of 14.2 [95% confidence interval (CI) of 13.2–15.3] per 1000 infants. Logistic regression analyses were carried out to identify VSD risk factors. Increased risk of VSDs was observed among infants born to mothers who abused alcohol [OR = 4.83; 95% CI 1.88–12.41], or smoked during pregnancy [OR = 1.35; 95% CI 1.02–1.80]. Maternal diabetes mellitus was also a significant risk factor [OR = 8.72; 95% CI 3.16–24.07], while maternal age, body mass index, folic acid and multivitamin intake were not associated with increased risk. Overall risks of VSDs for male babies were lower [OR = 0.67; 95% CI 0.52–0.88].

Estrogenic Mechanisms and Cardiac Responses Following Early Life Exposure to Bisphenol A (BPA) and Its Metabolite 4-Methyl-2,4-bis( p-hydroxyphenyl)pent-1-ene (MBP) in Zebrafish

Environmental exposure to Bisphenol A (BPA) has been associated with a range of adverse health effects, including on the cardiovascular system in humans. Lack of agreement on its mechanism(s) of action likely stem from comparisons between in vivo and in vitro test systems and potential multiple effects pathways. In rodents, in vivo, metabolic activation of BPA produces 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), which is reported to be up to 1000 times more potent as an estrogen than BPA. We investigated the estrogenic effects and estrogen receptor signaling pathway(s) of BPA and MBP following early life exposure using a transgenic, estrogen responsive (ERE-TG) zebrafish and a targeted morpholino approach to knockdown the three fish estrogen receptor (ER) subtypes. The functional consequences of BPA exposure on the cardiovascular system of zebrafish larvae were also examined. The heart atrioventricular valves and the bulbus arteriosus were primary target tissues for both BPA and MBP in the ERE-TG zebrafish, and MBP was approximately 1000-fold more potent than BPA as an estrogen in these tissues. Estrogen receptor knockdown with morpholinos indicated that the estrogenic responses in the heart for both BPA and MBP were mediated via an estrogen receptor 1 (esr1) dependent pathway. At the highest BPA concentration tested (2500 μg/L), alterations in the atrial:ventricular beat ratio indicated a functional impact on the heart of 5 days post fertilization (dpf) larvae, and there was also a significantly reduced heart rate in these larvae at 14 dpf. Our findings indicate that some of the reported adverse effects on heart function associated with BPA exposure (in mammals) may act through an estrogenic mechanism, but that fish are unlikely to be susceptible to adverse effects on heart development for environmentally relevant exposures.

Nkx genes establish second heart field cardiomyocyte progenitors at the arterial pole and pattern the venous pole through Isl1 repression

NKX2-5 is the most commonly mutated gene associated with human congenital heart defects (CHDs), with a predilection for cardiac pole abnormalities. This homeodomain transcription factor is a central regulator of cardiac development and is expressed in both the first and second heart fields (FHF and SHF). We have previously revealed essential functions of nkx2.5 and nkx2.7, two Nkx2-5 homologs expressed in zebrafish cardiomyocytes, in maintaining ventricular identity. However, the differential roles of these genes in the specific subpopulations of the anterior (aSHF) and posterior (pSHF) SHFs have yet to be fully defined. Here, we show that Nkx genes regulate aSHF and pSHF progenitors through independent mechanisms. We demonstrate that Nkx genes restrict proliferation of aSHF progenitors in the outflow tract, delimit the number of pSHF progenitors at the venous pole and pattern the sinoatrial node acting through Isl1 repression. Moreover, optical mapping highlights the requirement for Nkx gene dose in establishing electrophysiological chamber identity and in integrating the physiological connectivity of FHF and SHF cardiomyocytes. Ultimately, our results may shed light on the discrete errors responsible for NKX2-5-dependent human CHDs of the cardiac outflow and inflow tracts.

A potentially curative fetal intervention for hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) encapsulates a spectrum of complex congenital cardiovascular malformations involving varying degrees of underdevelopment of the left-sided heart structures. However, despite improved survival rates since the introduction of staged surgical reconstruction, treatment options for HLHS remain palliative rather than curative. A major limiting factor in the development of definitive curative therapy for HLHS is an incomplete understanding of its pathogenesis. Currently, the aetiology HLHS is best conceptualised by the 'flow theory' of cardiogenesis, which states that normal cardiac development is reliant on the interrelationship of normal flow patterns of blood through the developing heart, and appropriate growth of the cardiac valves and myocardium. Thus, congenital cardiac malformations, such as HLHS, are thought to arise when these two processes are incorrectly coupled in utero. The rationale for the hypothesis proposed herein rests upon the flow theory of cardiogenesis. Morphological studies of HLHS indicate that, although underdeveloped, all left-sided cardiac structures are present and anatomically correct. Further, of the various structural abnormalities that can occur within the spectrum of HLHS, the presence of a ventricular septal defect (VSD) is rare. The rarity of a VSD within the morphological spectrum of HLHS suggests the syndrome may not develop in the presence of a functionally significant VSD. Presumably, the presence of a functional VSD establishes a communication between the two ventricles during cardiac development, and preserves the normal pressure-flow-dependent growth of the left ventricular (LV) myocardium, despite inflow/outflow valve defects. It is proposed that surgical creation of a VSD in utero will 'rescue' the LV of hearts with left-sided valvular deformities that render them susceptible to the development of HLHS later in gestation. In evaluating this hypothesis, potential techniques for surgical creation of a VSD in utero are offered. These techniques are based on already established catheter-based in utero interventions, and conventional postnatal percutaneous procedures for VSD creation. Further discussion is also offered on techniques to avoid, and manage, potential complications (i.e. conduction system damage) of the proposed technique(s). Finally, if VSD creation in utero is indeed practically feasible, and successfully establishes the hypothesised hemodynamic and myocardial growth normalisation within the abnormally developing LV, the clinical implications are profound. This procedure may hold a potential cure for almost every sub-type of HLHS.

BMP2 expression in the endocardial lineage is required for AV endocardial cushion maturation and remodeling

Distal outgrowth, maturation and remodeling of the endocardial cushion mesenchyme in the atrioventricular (AV) canal are the essential morphogenetic events during four-chambered heart formation. Mesenchymalized AV endocardial cushions give rise to the AV valves and the membranous ventricular septum (VS). Failure of these processes results in several human congenital heart defects. Despite this clinical relevance, the mechanisms governing how mesenchymalized AV endocardial cushions mature and remodel into the membranous VS and AV valves have only begun to be elucidated. The role of BMP signaling in the myocardial and secondary heart forming lineage has been well studied; however, little is known about the role of BMP2 expression in the endocardial lineage. To fill this knowledge gap, we generated Bmp2 endocardial lineage-specific conditional knockouts (referred to as Bmp2 cKO^Endo) by crossing conditionally-targeted Bmp2^flox/flox mice with a Cre-driver line, Nfatc1^Cre, wherein Cre-mediated recombination was restricted to the endocardial cells and their mesenchymal progeny. Bmp2 cKO^Endo mouse embryos did not exhibit failure or delay in the initial AV endocardial cushion formation at embryonic day (ED) 9.5-11.5; however, significant reductions in AV cushion size were detected in Bmp2 cKO^Endo mouse embryos when compared to control embryos at ED13.5 and ED16.5. Moreover, deletion of Bmp2 from the endocardial lineage consistently resulted in membranous ventricular septal defects (VSDs), and mitral valve deficiencies, as evidenced by the absence of stratification of mitral valves at birth. Muscular VSDs were not found in Bmp2 cKO^Endo mouse hearts. To understand the underlying morphogenetic mechanisms leading to a decrease in cushion size, cell proliferation and cell death were examined for AV endocardial cushions. Phospho-histone H3 analyses for cell proliferation and TUNEL assays for apoptotic cell death did not reveal significant differences between control and Bmp2 cKO^Endo in AV endocardial cushions. However, mRNA expression of the extracellular matrix components, versican, Has2, collagen 9a1, and periostin was significantly reduced in Bmp2 cKO^Endo AV cushions. Expression of transcription factors implicated in the cardiac valvulogenesis, Snail2, Twist1 and Sox9, was also significantly reduced in Bmp2 cKO^Endo AV cushions. These data provide evidence that BMP2 expression in the endocardial lineage is essential for the distal outgrowth, maturation and remodeling of AV endocardial cushions into the normal membranous VS and the stratified AV valves.

Changes in the diagnosis of congenital cardiovascular malformations during the 1st year of life: impacts on epidemiological risk factor associations

Many epidemiological studies base their classification of congenital cardiovascular malformations in newborns upon a single, initial diagnosis. This study aimed to evaluate the effect of subsequent diagnostic investigations on the results of epidemiological studies. We used diagnostic codes from the Baltimore-Washington Infant Study from the time of birth and at ~1 year of age. Odds ratios and 95% confidence intervals were used to identify associations between changes in diagnoses and infant characteristics, time period, that is, before and after introduction of color flow Doppler imaging, and diagnostic variables. Of the 3054 patients with data at both time points, 400 (13.1%) had diagnostic changes. For congenital cardiovascular malformations of early cardiogenesis, such as laterality and looping defects, conotruncal malformations, and atrioventricular septal defects, significant associations were observed between diagnostic change and case infants large for gestational age (odds ratio=0.22, p=0.01), diagnosed initially by echocardiography only (odds ratio=2.05, p=0.001), or with non-cardiac malformations (odds ratio=0.60, p=0.03). For all other congenital cardiovascular malformations, significant associations were observed with echocardiography-only diagnosis (odds ratio=1.43, p=0.04) and non-cardiac malformations (odds ratio=0.57, p<0.001). We found no statistically significant differences between risk factor odds ratios calculated using initial diagnoses versus those calculated using 1-year update diagnoses. Changes in congenital cardiovascular malformation diagnoses from birth to year 1 interval were significantly associated with infant characteristics and diagnostic modality but did not materially affect the outcome of risk factor associations.

Psychiatric Disorders in Adolescents With Single Ventricle Congenital Heart Disease

BACKGROUND AND OBJECTIVES

Mental health outcomes for survivors of critical congenital heart disease (CHD) remain under-investigated. We sought to examine psychiatric disorders and psychosocial functioning in adolescents with single ventricle CHD and to explore whether patient-related risk factors predict dysfunction.

METHODS

This cohort study recruited 156 adolescents with single ventricle CHD who underwent the Fontan procedure and 111 healthy referents. Participants underwent comprehensive psychiatric evaluation including a clinician-rated psychiatric interview and parent- and self-report ratings of anxiety, disruptive behavior, including attention-deficit/hyperactivity disorder (ADHD), and depressive symptoms. Risk factors for dysfunction included IQ, medical characteristics, and concurrent brain abnormalities.

RESULTS

Adolescents with single ventricle CHD had higher rates of lifetime psychiatric diagnosis compared with referents (CHD: 65%, referent: 22%; P < .001). Specifically, they had higher rates of lifetime anxiety disorder and ADHD (P < .001 each). The CHD group scored lower on the primary psychosocial functioning measure, the Children's Global Assessment Scale, than referents (CHD median [interquartile range]: 62 [54-66], referent: 85 [73-90]; P < .001). The CHD group scored worse on measures of anxiety, disruptive behavior, and depressive symptoms. Genetic comorbidity did not impact most psychiatric outcomes. Risk factors for anxiety disorder, ADHD, and lower psychosocial functioning included lower birth weight, longer duration of deep hypothermic circulatory arrest, lower intellectual functioning, and male gender.

CONCLUSIONS

Adolescents with single ventricle CHD display a high risk of psychiatric morbidity, particularly anxiety disorders and ADHD. Early identification of psychiatric symptoms is critical to the management of patients with CHD.

Biodegradable and biomimetic elastomeric scaffolds for tissue-engineered heart valves

Valvular heart diseases are the third leading cause of cardiovascular disease, resulting in more than 25,000 deaths annually in the United States. Heart valve tissue engineering (HVTE) has emerged as a putative treatment strategy such that the designed construct would ideally withstand native dynamic mechanical environment, guide regeneration of the diseased tissue and more importantly, have the ability to grow with the patient. These desired functions could be achieved by biomimetic design of tissue-engineered constructs that recapitulate in vivo heart valve microenvironment with biomimetic architecture, optimal mechanical properties and possess suitable biodegradability and biocompatibility. Synthetic biodegradable elastomers have gained interest in HVTE due to their excellent mechanical compliance, controllable chemical structure and tunable degradability. This review focuses on the state-of-art strategies to engineer biomimetic elastomeric scaffolds for HVTE. We first discuss the various types of biodegradable synthetic elastomers and their key properties. We then highlight tissue engineering approaches to recreate some of the features in the heart valve microenvironment such as anisotropic and hierarchical tri-layered architecture, mechanical anisotropy and biocompatibility.

STATEMENT OF SIGNIFICANCE

Heart valve tissue engineering (HVTE) is of special significance to overcome the drawbacks of current valve replacements. Although biodegradable synthetic elastomers have emerged as promising materials for HVTE, a mature HVTE construct made from synthetic elastomers for clinical use remains to be developed. Hence, this review summarized various types of biodegradable synthetic elastomers and their key properties. The major focus that distinguishes this review from the current literature is the thorough discussion on the key features of native valve microenvironments and various up-and-coming approaches to engineer synthetic elastomers to recreate these features such as anisotropic tri-layered architecture, mechanical anisotropy, biodegradability and biocompatibility. This review is envisioned to inspire and instruct the design of functional HVTE constructs and facilitate their clinical translation.

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.

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.

Increased systolic load causes adverse remodeling of fetal aortic and mitral valves

While abnormal hemodynamic forces alter fetal myocardial growth, little is known about whether such insults affect fetal cardiac valve development. We hypothesized that chronically elevated systolic load would detrimentally alter fetal valve growth. Chronically instrumented fetal sheep received either a continuous infusion of adult sheep plasma to increase fetal blood pressure, or a lactated Ringer's infusion as a volume control beginning on day 126 ± 4 of gestation. After 8 days, mean arterial pressure was higher in the plasma infusion group (63.0 mmHg vs. 41.8 mmHg, P < 0.05). Mitral annular septal-lateral diameter (11.9 mm vs. 9.1 mm, P < 0.05), anterior leaflet length (7.7 mm vs. 6.4 mm, P < 0.05), and posterior leaflet length (P2; 4.0 mm vs. 3.0 mm, P < 0.05) were greater in the elevated load group. mRNA levels of Notch-1, TGF-β2, Wnt-2b, BMP-1, and versican were suppressed in aortic and mitral valve leaflets; elastin and α1 type I collagen mRNA levels were suppressed in the aortic valves only. We conclude that sustained elevated arterial pressure load on the fetal heart valve leads to anatomic remodeling and, surprisingly, suppression of signaling and extracellular matrix genes that are important to valve development. These novel findings have important implications on the developmental origins of valve disease and may have long-term consequences on valve function and durability.

Heart valve tissue engineering: how far is the bedside from the bench?

Heart disease, including valve pathologies, is the leading cause of death worldwide. Despite the progress made thanks to improving transplantation techniques, a perfect valve substitute has not yet been developed: once a diseased valve is replaced with current technologies, the newly implanted valve still needs to be changed some time in the future. This situation is particularly dramatic in the case of children and young adults, because of the necessity of valve growth during the patient's life. Our review focuses on the current status of heart valve (HV) therapy and the challenges that must be solved in the development of new approaches based on tissue engineering. Scientists and physicians have proposed tissue-engineered heart valves (TEHVs) as the most promising solution for HV replacement, especially given that they can help to avoid thrombosis, structural deterioration and xenoinfections. Lastly, TEHVs might also serve as a model for studying human valve development and pathologies.

Tetralogy of Fallot and Hypoplastic Left Heart Syndrome - Complex Clinical Phenotypes Meet Complex Genetic Networks

In many cases congenital heart disease (CHD) is represented by a complex phenotype and an array of several functional and morphological cardiac disorders. These malformations will be briefly summarized in the first part focusing on two severe CHD phenotypes, hypoplastic left heart syndrome (HLHS) and tetralogy of Fallot (TOF). In most cases of CHD the genetic origin remains largely unknown, though the complexity of the clinical picture strongly argues against a dysregulation which can be attributed to a single candidate gene but rather suggests a multifaceted polygenetic origin with elaborate interactions. Consistent with this idea, genome-wide approaches using whole exome sequencing, comparative sequence analysis of multiplex families to identify de novo mutations and global technologies to identify single nucleotide polymorphisms, copy number variants, dysregulation of the transcriptome and epigenetic variations have been conducted to obtain information about genetic alterations and potential predispositions possibly linked to the occurrence of a CHD phenotype. In the second part of this review we will summarize and discuss the available literature on identified genetic alterations linked to TOF and HLHS.

Adolescents with tetralogy of Fallot: neuropsychological assessment and structural brain imaging

BACKGROUND

Few data are available on the neuropsychological, behavioural, or structural brain imaging outcomes in adolescents who underwent corrective surgery in infancy for tetralogy of Fallot.

METHODS

In this single-centre cross-sectional study, we enrolled 91 adolescents (13-16 years old) with tetralogy of Fallot and 87 referent subjects. Assessments included tests of academic achievement, memory, executive functions, visual-spatial skills, attention, and social cognition, as well as brain magnetic resonance imaging.

RESULTS

Genetic abnormalities or syndromes were present in 25% of tetralogy of Fallot patients, who had markedly greater neuropsychological morbidities than did patients without a syndrome. However, even patients without a syndrome performed significantly worse than the referent group or population norms in all of the neuropsychological domains assessed. In multivariable regression in those without a genetic/phenotypic syndrome, the strongest predictors of adverse late neurodevelopmental outcomes included a greater number of complications at the first operation, more total surgical complications across all operations, and occurrence of post-operative seizures. The presence of at least one abnormality on structural magnetic resonance imaging was more frequent in tetralogy of Fallot patients than the referent group (42% versus 8%).

CONCLUSIONS

Adolescents with tetralogy of Fallot are at increased neurodevelopmental risk and would benefit from ongoing surveillance and educational supports even after childhood.

Predictors of health-related quality of life in adolescents with tetralogy of Fallot

OBJECTIVE

To assess health-related quality of life (HRQoL) of adolescents with repaired tetralogy of Fallot (TOF) and whether impairments in HRQoL domains are associated with neurocognitive and medical factors.

STUDY DESIGN

Parents of subjects with TOF and healthy referents 13-16 years of age completed the Child Health Questionnaire-Parent Form 50, generating psychosocial (PsS) and physical (PhS) health summary scores. Adolescents completed the Child Health Questionnaire-Child Form 87 and concurrent in-person neurocognitive testing. We analyzed relationships of PsS and PhS scores with neurocognitive performance and medical factors.

RESULTS

Compared with referents (n = 85), adolescents with TOF without a genetic diagnosis (n = 66) had lower PsS (50.9 ± 9.4 vs 57.2 ± 4.2, P < .001) and PhS scores (49.4 ± 9.5 vs 55.8 ± 4.9; P < .001). Compared with a normative sample, these adolescents with TOF had similar PsS scores (P = .52) but significantly lower PhS scores (P = .01). Within adolescents with TOF without genetic disorders, lower PsS scores were highly associated with worse neurocognitive measures, particularly the parent-reported Behavior Rating Inventory of Executive Function composite (r = -0.66, P < .001) and Parent Conners' attention deficit-hyperactivity disorder Index T score (r = -0.54, P < .001), whereas associations of PhS scores with neurocognitive measures were weaker.

CONCLUSIONS

Psychosocial health status in adolescents with TOF without genetic disorders was worse than in healthy referents without risk factors for brain injury but similar to a normative sample; physical health status was worse in these adolescents than in either comparison group. Within these subjects with TOF, worse psychosocial health status was most highly associated with concurrent executive dysfunction and attention deficit-hyperactivity disorder. Optimizing HRQoL constitutes another indication for attention to neurodevelopment in children with congenital heart disease.

Mediation analysis of gestational age, congenital heart defects, and infant birth-weight

BACKGROUND

In this study we assessed the mediation role of the gestational age on the effect of the infant's congenital heart defects (CHD) on birth-weight.

METHODS

We used secondary data from the Baltimore-Washington Infant Study (1981-1989). Mediation analysis was employed to investigate whether gestational age acted as a mediator of the association between CHD and reduced birth-weight. We estimated the mediated effect, the mediation proportion, and their corresponding 95% confidence intervals (CI) using several methods.

RESULTS

There were 3362 CHD cases and 3564 controls in the dataset with mean birth-weight of 3071 (SD = 729) and 3353 (SD = 603) grams, respectively; the mean gestational age was 38.9 (SD = 2.7) and 39.6 (SD = 2.2) weeks, respectively. After adjusting for covariates, the estimated mediated effect by gestational age was 113.5 grams (95% CI, 92.4-134.2) and the mediation proportion was 40.7% (95% CI, 34.7%-46.6%), using the bootstrap approach.

CONCLUSIONS

Gestational age may account for about 41% of the overall effect of heart defects on reduced infant birth-weight. Improved prenatal care and other public health efforts that promote full term delivery, particularly targeting high-risk families and mothers known to be carrying a fetus with CHD, may therefore be expected to improve the birth-weight of these infants and their long term health.

The Q510E mutation in Shp2 perturbs heart valve development by increasing cell migration

Tightly regulated cellular signaling is critical for correct heart valve development, but how and why signaling is dysregulated in congenital heart disease is not very well known. We focused on protein tyrosine phosphatase Shp2, because mutations in this signaling modulator frequently cause valve malformations associated with Noonan syndrome or Noonan syndrome with multiple lentigines (NSML). To model NSML-associated valve disease, we targeted overexpression of Q510E-Shp2 to mouse endocardial cushions (ECs) using a Tie2-Cre-based approach. At midgestation, Q510E-Shp2 expression increased the size of atrioventricular ECs by 80%. To dissect the underlying cellular mechanisms, we explanted ECs from chick embryonic hearts and induced Q510E-Shp2 expression using adenoviral vectors. Valve cell outgrowth from cultured EC explants into surrounding matrix was significantly increased by Q510E-Shp2 expression. Because focal adhesion kinase (FAK) is a critical regulator of cell migration, we tested whether FAK inhibition counteracts the Q510E-Shp2-induced effects in explanted ECs. The FAK/src inhibitor PP2 normalized valve cell outgrowth from Q510E-Shp2-expressing ECs. Next, chick ECs were further dissociated to assess cell proliferation and migration. Valve cell proliferation was not increased by Q510E-Shp2 as determined by label incorporation. In contrast, valve cell migration as reflected in a wound-healing assay was increased by Q510E-Shp2 expression, indicating that increased migration is the predominant effect of Q510E-Shp2 expression in ECs. In conclusion, PP2-sensitive signaling mediates the pathogenic effects of Q510E-Shp2 on cell migration in EC explant cultures. This suggests a central role for FAK and provides new mechanistic insight into the molecular basis of valve defects in NSML.

Epidemiology of Cardiovascular Malformations among Newborns in Monchegorsk (North-West Russia): a Register-Based Study

BACKGROUND

Cardiovascular malformations (CVM) are one of the most prevalent groups of birth defects. Knowledge about the prevalence, distribution and survival in Russia has been limited. The aim of our study was to assess the perinatal prevalence, structure and risk factors for CVM among newborns in Monchegorsk (Murmansk Oblast, Russia) and the mortality among the affected newborns in the period 1973-2008.

DESIGN AND METHODS

A register-based study on data from the Kola and Murmansk County Birth Registers. The study included 28,511 births.

RESULTS

The registered perinatal prevalence was 3.0 per 1000 new-borns, with septal defects as the most prevalent. CVM was twenty times more prevalent among stillborn than live born, and one-third of the live born with a CVM died during the first week of life. The perinatal mortality rate with CVM was 442 per 1000 newborns. This indicator decreased over time. The mothers of newborns with a CVM were ten times more likely to have stillbirth in their anamnesis. The adjusted odds ratio between maternal smoking during pregnancy and CVM was 4.09 [95% confidence interval: 1.75-9.53].

CONCLUSIONS

The diagnosed perinatal prevalence was relatively low. A previous stillbirth by the mother was highly associated with being born with a CVM. An adjusted elevated risk was also observed among smoking mothers. Perinatal survival increased over time, but varied to a large extent between the different types of CVM. Significance for public healthCardiovascular malformation is one of the most common groups of birth defects. It is considered an important public health issue, as these malformations are the main cause of infant deaths in developed countries. Precise estimates about the prevalence and perinatal survival are needed to organise and plan health care for such newborns. Our study is the first report from the Russian Federation based on data from population-based birth registers.

Critical review of the epidemiologic literature regarding the association between congenital heart defects and exposure to trichloroethylene

The most recent Integrated Risk Information System review of trichloroethylene (TCE; CAS# 79-01-6) has suggested that congenital heart defects (CHD) are a critical endpoint associated with exposure to this solvent. This conclusion was drawn, at least partly, from epidemiologic data, including several relatively recent studies. The current article critically reviews this epidemiologic literature, focusing on study quality and consistency. Literature searches uncovered approximately a dozen studies that specifically addressed associations between TCE and congenital malformations in eight populations. Four of these reported positive associations between TCE and heart defects, with significant relative risks as high as 5-6 in some subgroups. However, each of the positive studies had substantial design or analytical flaws that could easily explain the results, thereby limiting the conclusions that can be drawn. Five studies found no positive association with TCE, and several of these reported substantially fewer cases than expected despite similar/higher exposures compared to positive studies, further detracting from causal conclusions. Overall, this epidemiologic literature provides no substantive or consistent evidence linking TCE to CHD.

Potential effects of environmental chemical contamination in congenital heart disease

There is compelling evidence that prenatal exposures to environmental xenobiotics adversely affect human development and childhood. Among all birth defects, congenital heart disease (CHD) is the most prevalent of all congenital malformations and remains the leading cause of death. It has been estimated that in most cases the causes of heart defects remain unknown, while a growing number of studies have indicated the potential role of environmental agents as risk factors in CHD occurrence. In particular, maternal exposure to chemicals during the first trimester of pregnancy represents the most critical window of exposure for CHD. Specific classes of xenobiotics (e.g. organochlorine pesticides, organic solvents, air pollutants) have been identified as potential risk factors for CHD. Nonetheless, the knowledge gained is currently still incomplete as a consequence of the frequent heterogeneity of the methods applied and the difficulty in estimating the net effect of environmental pollution on the pregnant mother. The presence of multiple sources of pollution, both indoor and outdoor, together with individual lifestyle factors, may represent a further confounding element for association with the disease. A future new approach for research should probably focus on individual measurements of professional, domestic, and urban exposure to physical and chemical pollutants in order to accurately retrace the environmental exposure of parents of affected offspring during the pre-conceptional and pregnancy periods.

Congenital heart defects after maternal fever

OBJECTIVE

The purpose of this study was to evaluate whether maternal febrile illnesses in early pregnancy are associated with increased risk for congenital heart defects in the offspring and whether such risk is mitigated by multivitamin supplement use.

STUDY DESIGN

From a multistate population-based case-control study (National Birth Defects Prevention Study), we compared maternal reports of first-trimester febrile illness from 7020 subjects with heart defects and 6746 unaffected control subjects who were born from 1997 through 2005. Relative risks were computed with no fever or infection during the first trimester as reference group and were adjusted for potential confounders.

RESULTS

First-trimester febrile illness was reported by 7.4% of control mothers (1 in 13). Febrile genitourinary infections were associated with selected heart defects, particularly right-sided obstructive defects (odds ratios, >3) and possibly others, whereas common respiratory illnesses were associated with low-to-negligible risks for most heart defects. When risk estimates were elevated, they tended to be mitigated when multivitamin supplements had been taken in the periconceptional period.

CONCLUSION

The source of fever and the use of supplements appear to influence the risk for heart defects. This information can be helpful in counseling and research, in particular with regard to primary prevention.

The hLAMP-1-positive particulate matrix involved in cardiac mesenchyme formation in the chick does not include BMP-2

Early heart development involves the transformation of endocardial cells in the atrioventricular canal and outflow tract regions into mesenchymal cells, a process called endocardial mesenchymal transformation (EMT). This process is initiated by factors, termed the particulate matrix, that are secreted by the myocardium. The particulate matrix causes a subset of endocardial cells to hypertrophy, lose their cell-cell contacts, form migratory processes, transform into mesenchymal cells, and migrate into the underlying endocardial cushions. The particulate matrix can be extracted using EDTA and the EDTA extract can initiate the EMT process. Earlier reports from our laboratory have shown that the particulate matrix can be detected with the hLAMP-1 antibody in immunostaining and Western blot analysis. In addition, similar proteins have been isolated from the growth media of stage 15-16 chick embryo myocardial cultures (MyoCM). Since other investigators have identified a possible role for bone morphogenetic protein (BMP)-2 during the EMT process in the heart, we asked whether BMP-2 is a part of the chick hLAMP-1-positive particulate matrix. To answer this question, we double stained stage 15-16 chick embryo sections with hLAMP-1 and BMP-2 antibodies. We found that BMP-2 signals do not colocalize with hLAMP-1-stained particles. In addition, using immunoprecipitation-Western blot analysis, we demonstrated no association of BMP-2 with the hLAMP-1-bound fraction of the EDTA extract or MyoCM. Our results indicate that BMP-2 is not a component of the hLAMP-1-positive particulate matrix in the chick.

The contribution of de novo and rare inherited copy number changes to congenital heart disease in an unselected sample of children with conotruncal defects or hypoplastic left heart disease

Congenital heart disease (CHD) is the most common congenital malformation, with evidence of a strong genetic component. We analyzed data from 223 consecutively ascertained families, each consisting of at least one child affected by a conotruncal defect (CNT) or hypoplastic left heart disease (HLHS) and both parents. The NimbleGen HD2-2.1 comparative genomic hybridization platform was used to identify de novo and rare inherited copy number variants (CNVs). Excluding 10 cases with 22q11.2 DiGeorge deletions, we validated de novo CNVs in 8 % of 148 probands with CNTs, 12.7 % of 71 probands with HLHS and none in 4 probands with both. Only 2 % of control families showed a de novo CNV. We also identified a group of ultra-rare inherited CNVs that occurred de novo in our sample, contained a candidate gene for CHD, recurred in our sample or were present in an affected sibling. We confirmed the contribution to CHD of copy number changes in genes such as GATA4 and NODAL and identified several genes in novel recurrent CNVs that may point to novel CHD candidate loci. We also found CNVs previously associated with highly variable phenotypes and reduced penetrance, such as dup 1q21.1, dup 16p13.11, dup 15q11.2-13, dup 22q11.2, and del 2q23.1. We found that the presence of extra-cardiac anomalies was not related to the frequency of CNVs, and that there was no significant difference in CNV frequency or specificity between the probands with CNT and HLHS. In agreement with other series, we identified likely causal CNVs in 5.6 % of our total sample, half of which were de novo.

Tetralogy of Fallot: epidemiology meets real-world management: lessons from the Baltimore-Washington Infant Study

Decades ago, mass-scale epidemiologic studies were undertaken to accurately describe the prevalence of congenital heart disease and associated malformations, and to identify inheritance patterns, teratogenic influence and aetiologic underpinnings. Despite phenomenal breakthroughs in molecular diagnosis of congenital heart disease, original population-based studies for detailed knowledge of prevalence, associated malformations, and appropriate patient and family counselling remain invaluable to the armamentarium and knowledge base of paediatric cardiologists. No modern-era studies have supplanted the importance of the Baltimore-Washington Infant Study undertaken from 1981 to 1989. In this article, we reprise the findings of the Baltimore-Washington Infant Study in tetralogy of Fallot, as well as to review current molecular diagnosis.

The role of pygopus in the differentiation of intracardiac valves in Drosophila

Cardiac valves serve an important function; they support unidirectional blood flow and prevent blood regurgitation. Wnt signaling plays an important role in the formation of mouse cardiac valves and cardiac valve proliferation in Zebrafish, but identification of the specific signaling components involved has not been addressed systematically. Of the components involved in Wnt signal transduction, pygopus (pygo), first identified as a core component of Wnt signaling in Drosophila, has not yet to be investigated with respect to valve development and differentiation. Here, we take advantage of the Drosophila heart model to study the role of pygo in formation of valves between the cardiac chambers. We found that cardiac-specific pygo knockdown in the Drosophila heart causes dilation in the region of these cardiac valves, and their characteristic dense mesh of myofibrils does not form and resembles that of neighboring cardiomyocytes. In contrast, heart-specific knockdown of the transcription factors, arm/β-Cat, lgs/BCL9, or pan/TCF, which mediates canonical Wnt signal transduction, shows a much weaker valve differentiation defect. Double-heterozygous combinations of mutants for pygo and the Wnt-signaling components have no additional effect on heart function compared with pygo heterozygotes alone. These results are consistent with the idea that pygo functions independently of canonical Wnt signaling in the differentiation of the adult interchamber cardiac valves.

Environmental origins of congenital heart disease: the heart-placenta connection

Although the mammalian embryo is well protected in the uterus, environmental chemicals, drugs, and maternal nutritional imbalances can interfere with regulatory pathways directing placental and embryonic development early in gestation. Embryonic cells are most susceptible to environmental influences during cellular specification and differentiation stages. Because biochemical differentiation precedes morphological outcome often by days, the period of susceptibility to environmental chemicals expectedly precedes visible morphogenic effects. The cellular mechanisms by which drugs and other environmental factors disrupt embryonic development and induce cardiac abnormalities have remained undefined.

Materials and manufacturing technologies available for production of a pediatric bioabsorbable stent

Transcatheter treatment of children with congenital heart disease such as coarctation of the aorta and pulmonary artery stenosis currently involves the use of metal stents. While these provide good short term results, there are long term complications with their use. Children outgrow metal stents, obligating them to future transcatheter dilations and eventual surgical removal. A bioabsorbable stent, or a stent that goes away with time, would solve this problem. Bioabsorbable stents are being developed for use in coronary arteries, however these are too small for use in pediatric congenital heart disease. A bioabsorbable stent for use in pediatric congenital heart disease needs to be low profile, expandable to a diameter 8 mm, provide sufficient radial strength, and absorb quickly enough to allow vessel growth. Development of absorbable coronary stents has led to a great understanding of the available production techniques and materials such as bioabsorbable polymers and biocorrodable metals. Children with congenital heart disease will hopefully soon benefit from the current generation of bioabsorbable and biocorrodable materials and devices.