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

Assessing Left Ventricular Pathology in Patients with Ebstein Anomaly Using Cardiovascular Magnetic Resonance: Looking Past the Right Heart

Ebstein Anomaly (EA) is a malformation of the right heart, but there is data to suggest that the left ventricle (LV) can suffer from intrinsic structural and functional abnormalities which affect surgical outcomes. The LV in patients with EA is hypertrabeculated with abnormalities in LV function and strain. In this retrospective single-center study, patients with EA who underwent pre-operative cardiac MRI (CMR) between the periods of 2014-2024 were included along with a group of healthy-age-matched controls. Left ventricular and right ventricular volume, function and strain analyses were performed on standard SSFP imaging. LV noncompacted: compacted (NC/C) ratio and the displacement index of the tricuspid valve were measured. Forty-seven EA patients were included with mean age of 21.0 ± 17.6 years. Seventeen EA patients (36%) had mild pre-operative LV dysfunction on CMR and 1 (2.1%) had moderate LV dysfunction. Out of these 18 patients with LV dysfunction, only 2 were detected to have dysfunction on Echocardiogram. The global circumferential and longitudinal strain were significantly lower in the reduced LVEF group compared to those with preserved LVEF (- 14.8% vs. - 17%, p = 0.02 and - 11.9% vs. - 15.0%; p = 0.05; respectively) on CMR. A single EA patient met criteria for LVNC with a maximal NC/C ratio > 2.3. There was no statistically significant difference in NC/C ratio in the EA population (1.4 ± 0.6) vs. controls (1.1 ± 0.2), p = 0.17. There was an inverse correlation of LV ejection fraction with right ventricular end-diastolic volume and displacement index. All patients underwent the Da Silva Cone procedure at our center. Patients with preoperative LV dysfunction had longer duration of epinephrine use in the immediate postoperative period (33.7 ± 21.4 vs 10.2 ± 25.6 h, p = 0.02) and longer length of hospital stay (6.3 ± 3.2 vs 4.4 ± 1.2 days, p = 0.01). This is the largest study to date to evaluate preoperative LV structure and function in EA patients by CMR. In this cohort of 47 patients, preoperative LV dysfunction is fairly common and CMR has high sensitivity in detecting LV dysfunction as compared to Echo. True LV non-compaction was rare in this cohort. The presence of LV dysfunction is relevant to perioperative management and further study with larger cohorts and longer follow up are necessary.

Evaluation and Management of Chronic Heart Failure in Children and Adolescents With Congenital Heart Disease: A Scientific Statement From the American Heart Association

With continued medical and surgical advancements, most children and adolescents with congenital heart disease are expected to survive to adulthood. Chronic heart failure is increasingly being recognized as a major contributor to ongoing morbidity and mortality in this population as it ages, and treatment strategies to prevent and treat heart failure in the pediatric population are needed. In addition to primary myocardial dysfunction, anatomical and pathophysiological abnormalities specific to various congenital heart disease lesions contribute to the development of heart failure and affect potential strategies commonly used to treat adult patients with heart failure. This scientific statement highlights the significant knowledge gaps in understanding the epidemiology, pathophysiology, staging, and outcomes of chronic heart failure in children and adolescents with congenital heart disease not amenable to catheter-based or surgical interventions. Efforts to harmonize the definitions, staging, follow-up, and approach to heart failure in children with congenital heart disease are critical to enable the conduct of rigorous scientific studies to advance our understanding of the actual burden of heart failure in this population and to allow the development of evidence-based heart failure therapies that can improve outcomes for this high-risk cohort.

Emerging Themes in Genetics of Hypertrophic Cardiomyopathy: Current Status and Clinical Application

Hypertrophic cardiomyopathy (HCM), defined clinically by the presence of unexplained left ventricular hypertrophy (LVH), with wall thickness ≥ 1.5 cm, is a phenotype in search of a diagnosis, which is most often a genetically determined, cardiac exclusive, or systemic disorder. Familial evaluation and genetic testing are required for definitive diagnosis. The role of genetic findings in predicting development of disease, outcomes, and increasingly to guide management is evolving with access to larger data sets. The specific mutation and sex of the patient are important determinants that ultimately are likely to guide management. The genetic/familial evaluation is influenced by the accuracy of the clinical diagnosis and the extent/expertise of the genetic laboratory. Genetic testing in a patient with unexplained LVH without systemic manifestations will yield a definite/likely pathogenetic mutation in a sarcomere (30%-50%), regulatory/functional (10%-15%) or metabolic/syndromic (< 5%) gene associated with Mendelian inheritance. The importance of oligo- and polygenic determinants, usually in the absence of Mendelian inheritance, is under investigation with important implications, particularly related to familial evaluation and definition of risk of disease development in relatives of probands. The results of genetic testing are increasingly important in management strategies related to the use of the implantable cardioverter defibrillator for prevention of sudden death, use of myosin inhibitors for refractory symptoms in patients with and without outflow tract obstruction, and-on the immediate horizon-gene therapy. This review will focus on genetic and outcome data in sarcomeric HCM, and minor causative genes with robust evidence of their association will also be considered.

Myosin Heavy Chain 7 (MYH7) Variant Associated Cardiovascular Disease: An Unusual Case of Heart Failure in a Young Male

A 37-year-old male with type two diabetes presented to the hospital with new-onset heart failure and renal dysfunction. His left ventricular (LV) ejection fraction was less than 10%. Transthoracic echocardiography and cardiovascular magnetic resonance (CMR) imaging also revealed severe bicuspid aortic valve stenosis, dilated cardiomyopathy with LV hypertrophy, prominent LV trabeculations, and features suggestive of mild myocarditis with active inflammation. While myocarditis was suspected on CMR imaging, his mild degree of myocardial involvement did not explain the entirety of his clinical presentation, degree of LV dysfunction, or other structural abnormalities. An extensive work-up for his LV dysfunction was unremarkable for ischemic, metabolic, infiltrative, infectious, toxic, oncologic, connective tissue, and autoimmune etiologies. Genetic testing was positive for a myosin heavy chain 7 (MYH7) variant, which was deemed likely to be a unifying etiology underlying his presentation. The MYH7 sarcomere gene allows beta-myosin expression in heart ventricles, with variants associated with hypertrophic and dilated cardiomyopathies, congenital heart diseases, myocarditis, and excessive trabeculation (formerly known as left ventricular noncompaction). This case highlights the diverse array of cardiac pathologies that can present with MYH7 gene variants and reviews an extensive work-up for this unusual presentation of heart failure in a young patient.

MYH7 in cardiomyopathy and skeletal muscle myopathy

Myosin heavy chain gene 7 (MYH7), a sarcomeric gene encoding the myosin heavy chain (myosin-7), has attracted considerable interest as a result of its fundamental functions in cardiac and skeletal muscle contraction and numerous nucleotide variations of MYH7 are closely related to cardiomyopathy and skeletal muscle myopathy. These disorders display significantly inter- and intra-familial variability, sometimes developing complex phenotypes, including both cardiomyopathy and skeletal myopathy. Here, we review the current understanding on MYH7 with the aim to better clarify how mutations in MYH7 affect the structure and physiologic function of sarcomere, thus resulting in cardiomyopathy and skeletal muscle myopathy. Importantly, the latest advances on diagnosis, research models in vivo and in vitro and therapy for precise clinical application have made great progress and have epoch-making significance. All the great advance is discussed here.

Human Genetics of Ebstein Anomaly

Ebstein anomaly (EA) is a rare, congenital cardiac defect of the tricuspid valve with a birth prevalence between 0.5 and 1 in 20,000 [1]. It is characterized by displacement of the tricuspid valve toward the apex of the right ventricle (RV) and "atrialization" of the RV (Fig. 57.1) [2]. EA accounts for about 0.5% of all congenital heart diseases (CHD) [2]. Depending on severity of the defect and due to heterogeneity of the disease, patient's presentation varies from severe heart failure symptoms and arrhythmia in neonatal life to asymptomatic adults.

Prenatal Diagnosis of Isolated Right Ventricular Non-Compaction Cardiomyopathy with an MYH7 Likely Pathogenic Variant

Background: Noncompaction of ventricular myocardium is a cardiomyopathy that typically involves the left ventricle or both ventricles; it has often been associated with mutations in genes encoding sarcomere proteins. Little is known about isolated right ventricular noncompaction, as only a few cases have been reported. Case Report: A 30 year old G2P1 woman experienced a spontaneous fetal loss at 19 weeks and 4 days. An ultrasound examination at 19 weeks showed right ventricular and tricuspid valve abnormalities, ascites, and early hydrops. At autopsy, the right ventricular chamber was dilated with numerous prominent trabeculations and deep intrabecular recesses as well as a dysplastic tricuspid valve. Histologic examination confirmed isolated right ventricular noncompaction. Whole exome sequencing showed a likely pathogenic variant in the MYH7 gene. Conclusions: This appears to be the first report of isolated right ventricular noncompaction associated with a gene mutation as well as the first diagnosis in a fetus.

MYH7 variants cause complex congenital heart disease

MYH7, encoding the myosin heavy chain sarcomeric β-myosin heavy chain, is a common cause of both hypertrophic and dilated cardiomyopathy. Additionally, families with left ventricular noncompaction cardiomyopathy (LVNC) and congenital heart disease (CHD), typically septal defects or Ebstein anomaly, have been identified to have heterozygous pathogenic variants in MHY7. One previous case of single ventricle CHD with heart failure due to a MYH7 variant has been identified. Herein, we present a single center's experience of complex CHD due to MYH7 variants. Three probands with a history of CHD, LVNC, and/or arrhythmias were identified to have MYH7 variants through multigene panel testing or exome sequencing. These three patients collectively had 12 affected family members, four with a history of Ebstein anomaly and seven with a history of LVNC. These findings suggest a wider phenotypic spectrum in MYH7-related CHD than previously understood. Further investigation into the possible role of MYH7 in CHD and mechanism of disease is necessary to fully delineate the phenotypic spectrum of MYH7-related cardiac disease. MYH7 should be considered for families with multiple individuals with complex CHD in the setting of a family history of LVNC or arrhythmias.

Left, but not right, ventricular status determines heart failure in adults with Ebstein anomaly - A case-control study based on magnetic resonance

BACKGROUND

Ebstein anomaly (EA) is a congenital heart defect affecting the right heart. Heart failure (HF) is a significant complication in adults with EA. It may result not only from the right ventricle (RV), but also from the left ventricle (LV) abnormalities. We evaluate the size and function of both ventricles in patients with EA in cardiac magnetic resonance (CMR); to assess their association with the clinical markers of HF.

METHODS

Study group: 37 unoperated adults with EA (mean age 43.0 ± 14.4y, 21[56.8%] males).

CONTROLS

25 volunteers (mean age 39.9 ± 10.9y, 15[60%] males). Study protocol included: CMR [ejection fraction (EF), end-diastolic (EDVind) and stroke volumes (SVind) indexed by body surface area]; cardiopulmonary test (peak VO2, %peak VO2, VE/VCO2 slope).

RESULTS

Size and systolic function of LV were reduced comparing to the controls [LVEDVind (ml/m2): 63.7(range 38.7-94.2) vs. 79.3(48.7-105.1), p < 0.001; LV SVind (ml/m2): 35.8(22.9-55.1) vs. 49.2(37.8-71.7), p < 0.0001; LVEF(%): 58.3(34-70.5) vs. 62.0(52.0-77.0), p = 0.009]. RV was enlarged comparing to the controls [RVEDVind (ml/m2): 124.3(52.8-378.9) vs. 83.0(64.0-102.0), p < 0.0001) with impaired systolic function (RV SVind (ml/m2): 22.7(11.1-74.1) vs. 48.0(37.8-71.7), p < 0.0001; RVEF(%): 38.0(21.0-66.1) vs. 59.0(49.0-69.0), p < 0.0001). A significant correlation was found between LVEDVind vs. peakVO2 (r = 0.52, p = 0.001); LV SVind vs. peakVO2 (r = 0.47,p = 0.005). There was no correlation between the right ventricular status and exercise capacity.

CONCLUSIONS

In adults with Ebstein anomaly the size of left ventricle is reduced, right ventricle is enlarged; the function of both is impaired. Abnormal exercise capacity is associated with left ventricular status. Ventricular interdependence probably plays a role in heart failure pathomechanism.

A Systematic Review of Ebstein’s Anomaly with Left Ventricular Noncompaction

Traditional definitions of Ebstein’s anomaly (EA) and left ventricular noncompaction (LVNC), two rare congenital heart defects (CHDs), confine disease to either the right or left heart, respectively. Around 15–29% of patients with EA, which has a prevalence of 1 in 20,000 live births, commonly manifest with LVNC. While individual EA or LVNC literature is extensive, relatively little discussion is devoted to the joint appearance of EA and LVNC (EA/LVNC), which poses a higher risk of poor clinical outcomes. We queried PubMed, Medline, and Web of Science for all peer-reviewed publications from inception to February 2022 that discuss EA/LVNC and found 58 unique articles written in English. Here, we summarize and extrapolate commonalities in clinical and genetic understanding of EA/LVNC to date. We additionally postulate involvement of shared developmental pathways that may lead to this combined disease. Anatomical variation in EA/LVNC encompasses characteristics of both CHDs, including tricuspid valve displacement, right heart dilatation, and left ventricular trabeculation, and dictates clinical presentation in both age and severity. Disease treatment is non-specific, ranging from symptomatic management to invasive surgery. Apart from a few variant associations, mainly in sarcomeric genes MYH7 and TPM1, the genetic etiology and pathogenesis of EA/LVNC remain largely unknown.

Expression Signatures of Long Noncoding RNAs in Left Ventricular Noncompaction

Long noncoding RNAs have gained widespread attention in recent years for their crucial role in biological regulation. They have been implicated in a range of developmental processes and diseases including cancer, cardiovascular, and neuronal diseases. However, the role of long noncoding RNAs (lncRNAs) in left ventricular noncompaction (LVNC) has not been explored. In this study, we investigated the expression levels of lncRNAs in the blood of LVNC patients and healthy subjects to identify differentially expressed lncRNA that develop LVNC specific biomarkers and targets for developing therapies using biological pathways. We used Agilent Human lncRNA array that contains both updated lncRNAs and mRNAs probes. We identified 1,568 upregulated and 1,141 downregulated (log fold-change > 2.0) lncRNAs that are differentially expressed between LVNC and the control group. Among them, RP11-1100L3.7 and XLOC_002730 are the most upregulated and downregulated lncRNAs. Using quantitative real-time reverse transcription polymerase chain reaction (RT-QPCR), we confirmed the differential expression of three top upregulated and downregulated lncRNAs along with two other randomly picked lncRNAs. Gene Ontology (GO) and KEGG pathways analysis with these differentially expressed lncRNAs provide insight into the cellular pathway leading to LVNC pathogenesis. We also identified 1,066 upregulated and 1,017 downregulated mRNAs. Gene set enrichment analysis (GSEA) showed that G2M, Estrogen, and inflammatory pathways are enriched in differentially expressed genes (DEG). We also identified miRNA targets for these differentially expressed genes. In this study, we first report the use of LncRNA microarray to understand the pathogenesis of LVNC and to identify several lncRNA and genes and their targets as potential biomarkers.

Overlap phenotypes of the left ventricular noncompaction and hypertrophic cardiomyopathy with complex arrhythmias and heart failure induced by the novel truncated DSC2 mutation

Background

The left ventricular noncompaction cardiomyopathy (LVNC) is a rare subtype of cardiomyopathy associated with a high risk of heart failure (HF), thromboembolism, arrhythmia, and sudden cardiac death.

Methods

The proband with overlap phenotypes of LVNC and hypertrophic cardiomyopathy (HCM) complicates atrial fibrillation (AF), ventricular tachycardia (VT), and HF due to the diffuse myocardial lesion, which were diagnosed by electrocardiogram, echocardiogram and cardiac magnetic resonance imaging. Peripheral blood was collected from the proband and his relatives. DNA was extracted from the peripheral blood of proband for high-throughput target capture sequencing. The Sanger sequence verified the variants. The protein was extracted from the skin of the proband and healthy volunteer. The expression difference of desmocollin2 was detected by Western blot.

Results

The novel heterozygous truncated mutation (p.K47Rfs*2) of the DSC2 gene encoding an important component of desmosomes was detected by targeted capture sequencing. The western blots showed that the expressing level of functional desmocollin2 protein (~ 94kd) was lower in the proband than that in the healthy volunteer, indicating that DSC2 p.K47Rfs*2 obviously reduced the functional desmocollin2 protein expression in the proband.

Conclusion

The heterozygous DSC2 p.K47Rfs*2 remarkably and abnormally reduced the functional desmocollin2 expression, which may potentially induce the overlap phenotypes of LVNC and HCM, complicating AF, VT, and HF.

Epidemiology of Pediatric Heart Failure in the USA-a 15-Year Multi-Institutional Study

The epidemiology of pediatric heart failure (HF) has been characterized for congenital heart disease (CHD) and cardiomyopathies (CM), but the impact of CM associated with CHD has not been studied. This study aims to describe the characteristics and outcomes of inpatient pediatric HF patients with CHD, CM, and CHD with CM (CHD + CM) across the USA. We included all HF patients with CM diagnoses with and without CHD using ICD 9/10 codes ≤ 19 years old from January 2004 to September 2019 using the Pediatric Health Information System database. We identified 67,349 unique patients ≤ 19 years old with HF, of which 87% had CHD, 7% had CHD + CM, and 6% had CM. Pediatric HF admissions increased significantly from 2004 to 2018 with an associated increase in extracorporeal circulatory support (ECLS) use. Heart transplantation (HTX) increased only in the CHD and CHD + CM groups. CHD patients required less ECLS with and without HTX; however, they had significantly higher inpatient mortality after those procedures than the other groups (p < 0.001). CM patients were older (median 115 months) and had the lowest inpatient mortality after HTX with and without ECLS (p < 0.05). CHD + CM showed the highest overall inpatient mortality (15%), and cumulative hospital billed charges (median US$ 541,374), all p < 0.001. Pediatric HF admissions have increased from 2004 to 2018. ECLS use and HTX have expanded in this population, with an associated decrease in inpatient mortality in the CHD and CM groups. CHD + CM patients are a growing population with the highest inpatient mortality.

Heart failure in the adult Ebstein patient

Ebstein anomaly comprises approximately 1% of all congenital heart diseases. It occurs when the tricuspid valve fails to properly delaminate from the right ventricle, resulting in a clinical spectrum of abnormal tricuspid valve morphology and right ventricular dysfunction. Due to the anatomy of the tricuspid valve and right ventricle, as well as associated right- and left-sided pathology, patients are at risk for both right and left ventricular failure and the associated symptoms of each. Ebstein patients are also at risk for atrial arrhythmias, due to the atrial enlargement intrinsic to the anatomy, as well as the presence of potential accessory pathways. Arrhythmias are generally poorly tolerated, particularly in the setting of ventricular dysfunction. Cyanosis may also be present in Ebstein patients, due to the common occurrence of atrial communications, which can exacerbate other symptoms of heart failure. Treatment of heart failure can be through pharmacologic and procedural interventions, depending on the underlying cause of heart failure. While early heart failure symptoms may be treated with medical management, most Ebstein patients will require surgery. Various surgical and catheter-based interventions targeting the tricuspid valve and the atrialized right ventricular tissue have been developed to help treat the underlying cause of the heart failure. The optimal timing of transcatheter and surgical intervention in the Ebstein patient to prevent or treat heart failure needs further study.

Cardiomyopathy in the peripartum period due to left ventricular non-compaction and association with Ebstein's anomaly: a case report

Background

Left ventricular non-compaction (LVNC) cardiomyopathy is a persistence of abnormal foetal myocardium and is a rare cause of cardiomyopathy in the peripartum period. Unlike other causes of peripartum cardiomyopathy which typically improve, LVNC has significant long-term personal and family implications and needs lifelong follow-up.

Case summary

We describe a unique case of a 30-year-old woman who developed cardiomyopathy in the peripartum period which was revealed on cardiovascular magnetic resonance imaging to be due to occult LVNC. Our patient also had Ebstein’s anomaly, which is a known LVNC association.

Discussion

Cardiomyopathy in the peripartum period can be a decompensation of previously asymptomatic subclinical cardiomyopathy. It is important to assess for LVNC in patients presenting with this. Cardiovascular magnetic resonance imaging is the gold-standard imaging modality and allows accurate diagnosis of LVNC, associated structural complications and rare associations such as Ebstein’s anomaly. Left ventricular non-compaction is irreversible and has implications for patients and their family members.

Myocardial Fibrosis in Pediatric Patients With Ebstein's Anomaly

BACKGROUND

Left ventricular dysfunction in Ebstein's anomaly (EA) is associated with higher mortality. The health of the left ventricular myocardium in children and adolescents with EA has not been investigated in detail.

METHODS

Patients with unrepaired EA who had undergone cardiac magnetic resonance imaging including T1 mapping were retrospectively reviewed. Patients were compared with age- and sex-matched controls. EA severity index was calculated using volumetric measurements at end diastole ([right atrial+atrialized right ventricular volumes]/[functional right ventricular+left atrial+left ventricular volumes]). Global circumferential and radial strain and as well as strain rate were examined using cardiac magnetic resonance feature tracking.

RESULTS

Twelve EA patients and an equal number of controls were included. Functional and atrialized right ventricular end-diastolic volumes were 84±15 and 21±13 mL/m², respectively. Late gadolinium enhancement, confined to the right ventricle, was found in 2 patients (16%). Left ventricular native T1 values and extracellular volume fractions were higher in patients compared with controls (1026±47 versus 956±40 ms, P=0.0004 and 28.5±3.4% versus 22.5±2.6%, P<0.001, respectively). Native T1 times correlated inversely with patients' age, body surface area, and O₂ saturations (r=-0.63, -0.62, and -0.91, respectively; P=0.02, P=0.02, and P<0.0001, respectively). EA severity index ranged between 0.15 and 0.94 and correlated with T1 values (r=0.76, P=0.003). Native T1 correlated with global circumferential strain (r=0.58, P=0.04) but not ejection fraction (EF). EA patients had reduced maximum oxygen uptake (Vo₂max). Vo₂max correlated inversely with T1 values (r=-0.79, P=0.01).

CONCLUSIONS

Children and adolescents with EA experience an abnormal degree of diffuse myocardial fibrosis. Its association with O₂ saturation points toward a role of hypoxemia in the pathogenesis of fibrosis. Larger and prospective studies are needed to evaluate the value of T1 mapping for risk stratification and monitoring in EA.

Left Ventricular Noncompaction Is More Prevalent in Ventricular Septal Defect Than Other Congenital Heart Defects: A Morphological Study

Left ventricular noncompaction (LVNC) is a condition characterized by prominent ventricular trabeculae and deep intertrabecular recesses and has been described as a possible substrate for arrhythmias, thromboembolism, and heart failure. Herein, we explored the prevalence of LVNC morphology among hearts with congenital heart defects (CHD). We examined 259 postnatal hearts with one of the following CHD: isolated ventricular septal defect (VSD); isolated atrial septal defect (ASD); atrioventricular septal defect (AVSD); transposition of the great arteries (TGA); isomerism of the atrial appendages (ISOM); Ebstein’s malformation (EB); Tetralogy of Fallot (TF). Eleven hearts from children who died of non-cardiovascular causes were used as controls. The thickness of the compacted and non-compacted left ventricular myocardial wall was determined and the specimens classified as presenting or not LVNC morphology according to three criteria, as proposed by Chin, Jenni, and Petersen. Normal hearts did not present LVNC, but the CHD group presented different percentages of LVNC in at least one diagnostic criterium. The prevalence of LVNC was respectively, according to Chin’s, Jenni´s and Petersen´s methods: for VSD—54.2%, 35.4%, and 12.5%; ASD—8.3%, 8.3%, and 8.3%; AVSD—2.9%, 2.9%, and 0.0%; TGA—22.6%, 17%, and 5.7%; ISOM—7.1%, 7.1%, and 7.1%; EB—28.6%, 9.5%, and 0.0%; TF—5.9%. 2.9%, and 2.9%. VSD hearts showed a significantly greater risk of presenting LVNC when compared to controls (Chin and Jenni criteria). No other CHD presented similar risk. Current results show some agreement with previous studies, such as LVNC morphology being more prevalent in VSDs. Nonetheless, this is a morphological study and cannot be correlated with symptoms or severity of the CHD.

Genetics of inherited cardiomyopathies in Africa

In sub-Saharan Africa (SSA), the burden of noncommunicable diseases (NCDs) is rising disproportionately in comparison to the rest of the world, affecting urban, semi-urban and rural dwellers alike. NCDs are predicted to surpass infections like human immunodeficiency virus, tuberculosis and malaria as the leading cause of mortality in SSA over the next decade. Heart failure (HF) is the dominant form of cardiovascular disease (CVD), and a leading cause of NCD in SSA. The main causes of HF in SSA are hypertension, cardiomyopathies, rheumatic heart disease, pericardial disease, and to a lesser extent, coronary heart disease. Of these, the cardiomyopathies deserve greater attention because of the relatively poor understanding of mechanisms of disease, poor outcomes and the disproportionate impact they have on young, economically active individuals. Morphofunctionally, cardiomyopathies are classified as dilated, hypertrophic, restrictive and arrhythmogenic; regardless of classification, at least half of these are inherited forms of CVD. In this review, we summarise all studies that have investigated the incidence of cardiomyopathy across Africa, with a focus on the inherited cardiomyopathies. We also review data on the molecular genetic underpinnings of cardiomyopathy in Africa, where there is a striking lack of studies reporting on the genetics of cardiomyopathy. We highlight the impact that genetic testing, through candidate gene screening, association studies and next generation sequencing technologies such as whole exome sequencing and targeted resequencing has had on the understanding of cardiomyopathy in Africa. Finally, we emphasise the need for future studies to fill large gaps in our knowledge in relation to the genetics of inherited cardiomyopathies in Africa.

Novel KLHL26 variant associated with a familial case of Ebstein's anomaly and left ventricular noncompaction

BACKGROUND

Ebstein's anomaly (EA) is a rare congenital heart disease of the tricuspid valve and right ventricle. Patients with EA often manifest with left ventricular noncompaction (LVNC), a cardiomyopathy. Despite implication of cardiac sarcomere genes in some cases, very little is understood regarding the genetic etiology of EA/LVNC. Our study describes a multigenerational family with at least 10 of 17 members affected by EA/LVNC.

METHODS

We performed echocardiography on all family members and conducted exome sequencing of six individuals. After identifying candidate variants using two different bioinformatic strategies, we confirmed segregation with phenotype using Sanger sequencing. We investigated structural implications of candidate variants using protein prediction models.

RESULTS

Exome sequencing analysis of four affected and two unaffected members identified a novel, rare, and damaging coding variant in the Kelch-like family member 26 (KLHL26) gene located on chromosome 19 at position 237 of the protein (GRCh37). This variant region was confirmed by Sanger sequencing in the remaining family members. KLHL26 (c.709C > T p.R237C) segregates only with EA/LVNC-affected individuals (FBAT p < .05). Investigating structural implications of the candidate variant using protein prediction models suggested that the KLHL26 variant disrupts electrostatic interactions when binding to part of the ubiquitin proteasome, specifically Cullin3 (CUL3), a component of E3 ubiquitin ligase.

CONCLUSION

In this familial case of EA/LVNC, we have identified a candidate gene variant, KLHL26 (p.R237C), which may have an important role in ubiquitin-mediated protein degradation during cardiac development.

Rare Variants in Genes Associated With Cardiomyopathy Are Not Common in Hypoplastic Left Heart Syndrome Patients With Myocardial Dysfunction

Myocardial dysfunction is a known risk factor for morbidity and mortality in hypoplastic left heart syndrome (HLHS). Variants in some transcription factor and contractility genes, which are known to cause cardiomyopathy, have previously been associated with impaired right ventricular function in some HLHS patients. The care of HLHS patients is resource demanding. Identifying genetic variants associated with myocardial dysfunction would be helpful in tailoring the follow-up and therapeutic strategies. We tested whether a commercial cardiomyopathy gene panel could serve as a diagnostic tool in a Finnish cohort of HLHS patients with impaired right ventricular function to identify potentially pathogenic variants associated with poor prognosis. None of the patients had pathogenic or likely pathogenic variants in the studied cardiomyopathy-associated genes. Thus, our approach of performing a cardiomyopathy gene panel to identify pathogenic variants as directly causal or as modifiers for worse outcomes in hypoplastic left heart syndrome is not useful in clinical practice at the moment.

Genetics, Clinical Features, and Long-Term Outcome of Noncompaction Cardiomyopathy

BACKGROUND

The clinical outcomes of noncompaction cardiomyopathy (NCCM) range from asymptomatic to heart failure, arrhythmias, and sudden cardiac death. Genetics play an important role in NCCM.

OBJECTIVES

This study investigated the correlations among genetics, clinical features, and outcomes in adults and children diagnosed with NCCM.

METHODS

A retrospective multicenter study from 4 cardiogenetic centers in the Netherlands classified 327 unrelated NCCM patients into 3 categories: 1) genetic, with a mutation in 32% (81 adults; 23 children) of patients; 2) probably genetic, familial cardiomyopathy without a mutation in 16% (45 adults; 8 children) of patients; or 3) sporadic, no family history, without mutation in 52% (149 adults; 21 children) of patients. Clinical features and major adverse cardiac events (MACE) during follow-up were compared across the children and adults.

RESULTS

MYH7, MYBPC3, and TTN mutations were the most common mutations (71%) found in genetic NCCM. The risk of having reduced left ventricular (LV) systolic dysfunction was higher for genetic patients compared with the probably genetic and sporadic cases (p = 0.024), with the highest risk in patients with multiple mutations and TTN mutations. Mutations were more frequent in children (p = 0.04) and were associated with MACE (p = 0.025). Adults were more likely to have sporadic NCCM. High risk for cardiac events in children and adults was related to LV systolic dysfunction in mutation carriers, but not in sporadic cases. Patients with MYH7 mutations had low risk for MACE (p = 0.03).

CONCLUSIONS

NCCM is a heterogeneous condition, and genetic stratification has a role in clinical care. Distinguishing genetic from nongenetic NCCM complements prediction of outcome and may lead to management and follow-up tailored to genetic status.

Identification of clinically relevant phenotypes in patients with Ebstein anomaly

BACKGROUND

Ebstein anomaly (EA) is a heterogeneous congenital heart defect (CHD), frequently accompanied by diverse cardiac and extracardiac comorbidities, resulting in a wide range of clinical outcomes.

HYPOTHESIS

Phenotypic characterization of EA patients has the potential to identify variables that influence prognosis and subgroups with distinct contributing factors.

METHODS

A comprehensive cross-sectional phenotypic characterization of 147 EA patients from one of the main referral institutions for CHD in Colombia was carried out. The most prevalent comorbidities and distinct subgroups within the patient cohort were identified through cluster analysis.

RESULTS

The most prevalent cardiac comorbidities identified were atrial septal defect (61%), Wolff-Parkinson-White syndrome (WPW; 27%), and right ventricular outflow tract obstruction (25%). Cluster analysis showed that patients can be classified into 2 distinct subgroups with defined phenotypes that determine disease severity and survival. Patients in cluster 1 represented a particularly homogeneous subgroup with a milder spectrum of disease, including only patients with WPW and/or supraventricular tachycardia (SVT). Cluster 2 included patients with more diverse cardiovascular comorbidities.

CONCLUSIONS

This study represents one of the largest phenotypic characterizations of EA patients reported. The data show that EA is a heterogeneous disease, very frequently associated with cardiovascular and noncardiovascular comorbidities. Patients with WPW and SVT represent a homogeneous subgroup that presents with a less severe spectrum of disease and better survival when adequately managed. This should be considered when searching for genetic causes of EA and in the clinical setting.

Left ventricular non-compaction with Ebstein anomaly attributed to a TPM1 mutation

Left ventricular non-compaction (cardiomyopathy) (LVN(C)) is a rare hereditary cardiac condition, resulting from abnormal embryonic myocardial development. While it mostly occurs as an isolated condition, association with other cardiovascular manifestations such as Ebstein anomaly (EA) has been reported. This congenital heart defect is characterized by downward displacement of the tricuspid valve and leads to diminished ventricular size and function. In an autosomal dominant LVN(C) family consisting of five affected individuals, of which two also presented with EA and three with mitral valve insufficiency, we pursued the genetic disease cause using whole exome sequencing (WES). WES revealed a missense variant (p.Leu113Val) in TPM1 segregating with the LVN(C) phenotype. TPM1 encodes α-tropomyosin, which is involved in myocardial contraction, as well as in stabilization of non-muscle cytoskeletal actin filaments. So far, LVN(C)-EA has predominantly been linked to pathogenic variants in MYH7. However, one sporadic LVN(C)-EA case with a de novo TPM1 variant has recently been described. We here report the first LVN(C)-EA family segregating a pathogenic TPM1 variant, further establishing the association between EA predisposition and TPM1-related LVN(C). Consequently, we recommend genetic testing for both MYH7 and TPM1 in patients or families in which LVN(C)/non-compaction and EA coincide.

Genetic testing in congenital heart disease: A clinical approach

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

The hypertrabeculated (noncompacted) left ventricle is different from the ventricle of embryos and ectothermic vertebrates

Ventricular hypertrabeculation (noncompaction) is a poorly characterized condition associated with heart failure. The condition is widely assumed to be the retention of the trabeculated ventricular design of the embryo and ectothermic (cold-blooded) vertebrates. This assumption appears simplistic and counterfactual. Here, we measured a set of anatomical parameters in hypertrabeculation in man and in the ventricles of embryos and animals. We compared humans with left ventricular hypertrabeculation (N=21) with humans with structurally normal left ventricles (N=54). We measured ejection fraction and ventricular trabeculation using cardiovascular MRI. Ventricular trabeculation was further measured in series of embryonic human and 9 animal species, and in hearts of 15 adult animal species using MRI, CT, or histology. In human, hypertrabeculated left ventricles were significantly different from structurally normal left ventricles by all structural measures and ejection fraction. They were far less trabeculated than human embryonic hearts (15-40% trabeculated volume versus 55-80%). Early in development all vertebrate embryos acquired a ventricle with approximately 80% trabeculations, but only ectotherms retained the 80% trabeculation throughout development. Endothermic (warm-blooded) animals including human slowly matured in fetal and postnatal stages towards ventricles with little trabeculations, generally less than 30%. Further, the trabeculations of all embryos and adult ectotherms were very thin, less than 50 μm wide, whereas the trabeculations in adult endotherms and in the setting of hypertrabeculation were wider by orders of magnitude. It is concluded in contrast to a prevailing assumption, the hypertrabeculated left ventricle is not like the ventricle of the embryo or of adult ectotherms. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

Loss of Function Mutations in NNT Are Associated With Left Ventricular Noncompaction

BACKGROUND

Left ventricular noncompaction (LVNC) is an autosomal-dominant, genetically heterogeneous cardiomyopathy with variable severity, which may co-occur with cardiac hypertrophy.

METHODS AND RESULTS

Here, we generated whole exome sequence data from multiple members from 5 families with LVNC. In 4 of 5 families, the candidate causative mutation segregates with disease in known LVNC genes MYH7 and TPM1. Subsequent sequencing of MYH7 in a larger LVNC cohort identified 7 novel likely disease causing variants. In the fifth family, we identified a frameshift mutation in NNT, a nuclear-encoded mitochondrial protein, not implicated previously in human cardiomyopathies. Resequencing of NNT in additional LVNC families identified a second likely pathogenic missense allele. Suppression of nnt in zebrafish caused early ventricular malformation and contractility defects, probably driven by altered cardiomyocyte proliferation. In vivo complementation studies showed that mutant human NNT failed to rescue nnt morpholino-induced heart dysfunction, indicating a probable haploinsufficiency mechanism.

CONCLUSIONS

Together, our data expand the genetic spectrum of LVNC and demonstrate how the intersection of whole exome sequence with in vivo functional studies can accelerate the identification of genes that drive human genetic disorders.

Inherited cardiomyopathies

Cardiomyopathies (ie, diseases of the heart muscle) are major causes of morbidity and mortality. A significant percentage of patients with cardiomyopathies have genetic-based, inheritable disease and, over the past 2 decades the genetic causes of these disorders have been increasingly discovered. The genes causing these disorders when they are mutated appear to encode proteins that frame a "final common pathway" for that specific disorder, but the specifics of the phenotype, including age of onset, severity, and outcome is variable for reasons not yet understood. The "final common pathways" for the classified forms of cardiomyopathy include the sarcomere in the primarily diastolic dysfunction disorders hypertrophic cardiomyopathy and restrictive cardiomyopathy, the linkage of the sarcomere and sarcolemma in the systolic dysfunction disorder dilated cardiomyopathy, and the desmosome in arrhythmogenic cardiomyopathy. Left ventricular noncompaction cardiomyopathy (LVNC) is an overlap disorder and it appears that any of these "final common pathways" can be involved depending on the specific form of LVNC. The genetics and mechanisms responsible for these clinical phenotypes will be described.

Genetics and disease of ventricular muscle

Cardiomyopathies are a heterogeneous group of heart muscle diseases associated with heart failure, arrhythmias, and death. Genetic variation has a critical role in the pathogenesis of cardiomyopathies, and numerous single-gene mutations have been associated with distinctive cardiomyopathy phenotypes. Contemporaneously with these discoveries, there has been enormous growth of genome-wide sequencing studies in large populations, data that show extensive genomic variation within every individual. The considerable allelic diversity in cardiomyopathy genes and in genes predicted to impact clinical expression of disease mutations indicates the need for a more nuanced interpretation of single-gene mutation in cardiomyopathies. These findings highlight the need to find new ways to interpret the functional significance of suites of genetic variants, as well as the need for new disease models that take global genetic variant burdens, epigenetic factors, and cardiac environmental factors into account.