Mutations in sarcomeric protein genes not only lead to cardiomyopathy but also to congenital cardiovascular malformations

Congenital Heart Disease and Risk of Cardiovascular Disease: A Meta-Analysis of Cohort Studies

Background Despite remarkable success in the surgical and medical management of congenital heart disease ( CHD ), some survivors still experience cardiovascular complications over the long term. The goal of this study was to evaluate the association between CHD and risk of cardiovascular disease ( CVD ) by conducting a meta-analysis of cohort studies. Methods and Results A systematic literature search of several databases was conducted through April 2018 to identify studies reporting the risk of CVD , stroke, heart failure, and coronary artery heart disease in CHD survivors. The quality of individual studies was assessed using the Newcastle-Ottawa scale. The overall risk estimates were pooled using fixed-effects meta-analysis. Subgroup analyses were performed to explore possible sources of heterogeneity. Nine cohort studies comprising 684 200 participants were included. The overall combined relative risks for people with CHD compared with the controls were 3.12 (95% CI, 3.01-3.24) for CVD , 2.46 (95% CI, 2.30-2.63) for stroke, 5.89 (95% CI, 5.58-6.21) for heart failure, and 1.50 (95% CI, 1.40-1.61) for coronary artery heart disease. Significant heterogeneity was detected across studies regarding these risk estimates. Heterogeneity in the risk estimate of CVD was explained by geographic region, type of study design, sample source, age composition, and controlled confounders. Conclusions This meta-analysis of cohort studies of CHD found an association of increased risk of CVD in later life, although we cannot determine whether this association is confounded by a risk factor profile of CVD among CHD survivors or whether CHD is an independent risk factor.

Heart failure in single right ventricle congenital heart disease: physiological and molecular considerations

Because of remarkable surgical and medical advances over the past several decades, there are growing numbers of infants and children living with single ventricle congenital heart disease (SV), where there is only one functional cardiac pumping chamber. Nevertheless, cardiac dysfunction (and ultimately heart failure) is a common complication in the SV population, and pharmacological heart failure therapies have largely been ineffective in mitigating the need for heart transplantation. Given that there are several inherent risk factors for ventricular dysfunction in the setting of SV in addition to probable differences in molecular adaptations to heart failure between children and adults, it is perhaps not surprising that extrapolated adult heart failure medications have had limited benefit in children with SV heart failure. Further investigations into the molecular mechanisms involved in pediatric SV heart failure may assist with risk stratification as well as development of targeted, efficacious therapies specific to this patient population. In this review, we present a brief overview of SV anatomy and physiology, with a focus on patients with a single morphological right ventricle requiring staged surgical palliation. Additionally, we discuss outcomes in the current era, risk factors associated with the progression to heart failure, present state of knowledge regarding molecular alterations in end-stage SV heart failure, and current therapeutic interventions. Potential avenues for improving SV outcomes, including identification of biomarkers of heart failure progression, implications of personalized medicine and stem cell-derived therapies, and applications of novel models of SV disease, are proposed as future directions.

Heart Failure in Pediatric Patients With Congenital Heart Disease

Heart failure (HF) is a complex clinical syndrome resulting from diverse primary and secondary causes and shared pathways of disease progression, correlating with substantial mortality, morbidity, and cost. HF in children is most commonly attributable to coexistent congenital heart disease, with different risks depending on the specific type of malformation. Current management and therapy for HF in children are extrapolated from treatment approaches in adults. This review discusses the causes, epidemiology, and manifestations of HF in children with congenital heart disease and presents the clinical, genetic, and molecular characteristics that are similar or distinct from adult HF. The objective of this review is to provide a framework for understanding rapidly increasing genetic and molecular information in the challenging context of detailed phenotyping. We review clinical and translational research studies of HF in congenital heart disease including at the genome, transcriptome, and epigenetic levels. Unresolved issues and directions for future study are presented.

Congenital heart defects are rarely caused by mutations in cardiac and smooth muscle actin genes

Background. Congenital heart defects (CHDs) often have genetic background due to missense mutations in cardiomyocyte-specific genes. For example, cardiac actin was shown to be involved in pathogenesis of cardiac septum defects and smooth muscle actin in pathogenesis of aortic aneurysm in combination with patent ductus arteriosus (PDA). In the present study, we further searched for mutations in human α-cardiac actin (ACTC1) and smooth muscle α-actin (ACTA2) genes as a possible cause of atrial septum defect type II (ASDII) and PDA. Findings. Total genomic DNA was extracted from peripheral blood of 86 individuals with ASDs and 100 individuals with PDA. Coding exons and flanking intron regions of ACTC1 (NM_005159.4) and ACTA2 (NM_001613) were amplified by PCR with specific primers designed according to the corresponding gene reference sequences. PCR fragments were directly sequenced and analyzed. Sequence analysis of ACTC1 and ACTA2 did not identify any nucleotide changes that altered the coding sense of the genes. In ACTC1 gene, we were able to detect one previously described nucleotide polymorphism (rs2307493) resulting in a synonymous substitution. The frequency of this SNP was similar in the study and control group, thus excluding it from the possible disease-associated variants. Conclusions. Our results confirmed that the mutations in ACTC1 gene are rare (at least <1%) cause of ASDII. Mutations in ACTA2 gene were not detected in patients with PDA, thus being excluded from the list of frequent PDA-associated genetic defects.

Compound heterozygous or homozygous truncating MYBPC3 mutations cause lethal cardiomyopathy with features of noncompaction and septal defects

Familial hypertrophic cardiomyopathy (HCM) is usually caused by autosomal dominant pathogenic mutations in genes encoding sarcomeric or sarcomere-associated cardiac muscle proteins. The disease mainly affects adults, although young children with severe HCM have also been reported. We describe four unrelated neonates with lethal cardiomyopathy, and performed molecular studies to identify the genetic defect. We also present a literature overview of reported patients with compound heterozygous or homozygous pathogenic MYBPC3 mutations and describe their clinical characteristics. All four children presented with feeding difficulties, failure to thrive, and dyspnea. They died from cardiac failure before age 13 weeks. Features of left ventricular noncompaction were diagnosed in three patients. In the fourth, hypertrabeculation was not a clear feature, but could not be excluded. All of them had septal defects. Two patients were compound heterozygotes for the pathogenic c.2373dup p.(Trp792fs) and c.2827C>T p.(Arg943*) mutations, and two were homozygous for the c.2373dup and c.2827C>T mutations. All patients with biallelic truncating pathogenic mutations in MYBPC3 reported so far (n=21) were diagnosed with severe cardiomyopathy and/or died within the first few months of life. In 62% (13/21), septal defects or a patent ductus arteriosus accompanied cardiomyopathy. In contrast to heterozygous pathogenic mutations, homozygous or compound heterozygous truncating pathogenic MYBPC3 mutations cause severe neonatal cardiomyopathy with features of left ventricular noncompaction and septal defects in approximately 60% of patients.

Ebstein anomaly associated with left ventricular noncompaction: an autosomal dominant condition that can be caused by mutations in MYH7

Left ventricular noncompaction (LVNC) is a relatively common genetic cardiomyopathy, characterized by prominent trabeculations with deep intertrabecular recesses in mainly the left ventricle. Although LVNC often occurs in an isolated entity, it may also be present in various types of congenital heart disease (CHD). The most prevalent CHD in LVNC is Ebstein anomaly, which is a rare form of CHD characterized by apical displacement and partial fusion of the septal and posterior leaflet of the tricuspid valve with the ventricular septum. Several reports of sporadic as well as familial cases of Ebstein anomaly associated with LVNC have been reported. Recent studies identified mutations in the MYH7 gene, encoding the sarcomeric β-myosin heavy chain protein, in patients harboring this specific phenotype. Here, we will review the association between Ebstein anomaly, LVNC and mutations in MYH7, which seems to represent a subtype of Ebstein anomaly with autosomal dominant inheritance and variable penetrance.

Genetic factors in non-syndromic congenital heart malformations

The genetic defect in most patients with non-syndromic congenital heart malformations (CHM) is unknown, although more than 40 different genes have already been implicated. Only a minority of CHM seems to be due to monogenetic mutations, and the majority occurs sporadically. The multifactorial inheritance hypothesis of common diseases suggesting that the cumulative effect of multiple genetic and environmental risk factors leads to disease, might also apply for CHM. We review here the monogenic disease genes with high-penetrance mutations, susceptibility genes with reduced-penetrance mutations, and somatic mutations implicated in non-syndromic CHM.

Knockdown of alpha myosin heavy chain disrupts the cytoskeleton and leads to multiple defects during chick cardiogenesis

Atrial septal defects are a common congenital heart defect in humans. Although mutations in different genes are now frequently being described, little is known about the processes and mechanisms behind the early stages of atrial septal development. By utilizing morpholino-induced knockdown in the chick we have analysed the role of alpha myosin heavy chain during early cardiogenesis in a temporal manner. Upon knockdown of alpha myosin heavy chain, three different phenotypes of the atrial septum were observed: (1) the atrial septum failed to initiate, (2) the septum was initiated but was growth restricted, or (3) incorrect specification occurred resulting in multiple septa forming. In addition, at a lower frequency, decreased alpha myosin heavy chain was found to give rise to an abnormally looped heart or an enlarged heart. Staining of the actin cytoskeleton indicated that many of the myofibrils in the knockdown hearts were not as mature as those observed in the controls, suggesting a mechanism for the defects seen. Therefore, these data suggest a role for alpha myosin heavy chain in modelling of the early heart and the range of defects to the atrial septum suggest roles in its initiation, specification and growth during development.