Clinical and genetic issues in dilated cardiomyopathy: a review for genetics professionals

What Do We Know about Peripartum Cardiomyopathy? Yesterday, Today, Tomorrow

Peripartum cardiomyopathy is a disease that occurs during or after pregnancy and leads to a significant decline in cardiac function in previously healthy women. Peripartum cardiomyopathy has a varying prevalence among women depending on the part of the world where they live, but it is associated with a significant mortality and morbidity in this population. Therefore, timely diagnosis, treatment, and monitoring of this disease from its onset are of utmost importance. Although many risk factors are associated with the occurrence of peripartum cardiomyopathy, such as conditions of life, age of the woman, nutrient deficiencies, or multiple pregnancies, the exact cause of its onset remains unknown. Advances in research on the genetic associations with cardiomyopathies have provided a wealth of data indicating a possible association with peripartum cardiomyopathy, but due to numerous mutations and data inconsistencies, the exact connection remains unclear. Significant insights into the pathophysiological mechanisms underlying peripartum cardiomyopathy have been provided by the theory of an abnormal 16-kDa prolactin, which may be generated in an oxidative stress environment and lead to vascular and consequently myocardial damage. Recent studies supporting this disease mechanism also include research on the efficacy of bromocriptine (a prolactin synthesis inhibitor) in restoring cardiac function in affected patients. Despite significant progress in the research of this disease, there are still insufficient data on the safety of use of certain drugs treating heart failure during pregnancy and breastfeeding. Considering the metabolic changes that occur in different stages of pregnancy and the postpartum period, determining the correct dosing regimen of medications is of utmost importance not only for better treatment and survival of mothers but also for reducing the risk of toxic effects on the fetus.

Prevalence of Genetically Associated Dilated Cardiomyopathy: A Systematic Literature Review and Meta-Analysis

Background

Dilated cardiomyopathy (DCM) is a leading cause of heart failure and cardiac transplantation globally. Disease-associated genetic variants play a significant role in the development of DCM. Accurately determining the prevalence of genetically associated DCM (genetic DCM) is important for developing targeted prevention strategies. This review synthesized published literature on the global prevalence of genetic DCM across various populations, focusing on two of the most common variants: titin (TTN) and myosin heavy chain 7 (MYH7).

Methods

MEDLINE® and Embase were searched from database inception to September 19, 2022 for English-language studies reporting the prevalence of genetic DCM within any population. Studies using family history as a proxy for genetic DCM were excluded.

Results

Of 2,736 abstracts, 57 studies were included. Among the global adult or mixed (mostly adults with few pediatric patients) DCM population, median prevalence was 20.2% (interquartile range (IQR): 16.3-36.0%) for overall genetic DCM, 11.4% (IQR: 8.2-17.8%) for TTN-associated DCM, and 3.2% (IQR: 1.8-5.2%) for MYH7-associated DCM. Global prevalence of overall pediatric genetic DCM within the DCM population was similar (weighted mean: 21.3%). Few studies reported data on the prevalence of genetic DCM within the general population.

Conclusions

Our study identified variable prevalence estimates of genetic DCM across different populations and geographic locations. The current evidence may underestimate the genetic contributions due to limited screening and detection of potential DCM patients. Epidemiological studies using long-read whole genome sequencing to identify structural variants or non-coding variants are needed, as well as large cohort datasets with genotype-phenotype correlation analyses.

Clinical Insights in RNA-Binding Protein Motif 20 Cardiomyopathy: A Systematic Review

Dilated cardiomyopathy (DCM) is a common cause of heart failure (HF) and heart transplantation (HTx), with genetic factors playing a significant role. In recent years, the RNA-binding protein motif 20 (RBM20), which affects the gene splicing of various proteins with different cellular functions, was identified as the first DCM gene with regulatory properties. Variants of RBM20 have been associated with severe forms of DCM. The aim of this critical systematic review was to analyse RBM20 cardiomyopathy clinical features and outcomes. According to PRISMA guidelines, a search was run in the PubMed, Scopus and Web of Science electronic databases using the following keywords: "RBM20"; "cardiomyopathy"; "arrhythmias"; "heart failure". A total of 181 records were screened, of which 27 studies were potentially relevant to the topic. Through the application of inclusion and exclusion criteria, eight papers reporting 398 patients with RBM20 pathogenic variants were analysed. The mean age at presentation was 41 years. Familiarity with cardiomyopathy was available in 59% of cases, with 55% of probands reporting a positive family history. Imaging data indicated a mild reduction of left ventricular ejection fraction (mean LVEF 40%), while tissue characterization was reported in 24.3% of cases, showing late gadolinium enhancement in 33% of patients. Composite outcomes of sustained monomorphic ventricular tachycardia or ventricular fibrillation occurred in 19.4% of patients, with 12% undergoing HTx. There were no gender differences in arrhythmic outcomes, while 96.4% of patients who underwent HTx were male. In conclusion, RBM20 cardiomyopathy exhibits a severe phenotypic expression, both in terms of arrhythmic burden and HF progression.

Familial dilated cardiomyopathy in a child: a case report

BACKGROUND

Dilated cardiomyopathy (DCM) commonly leads to heart failure (HF) and represents the most common indication for cardiac transplantation in the pediatric population. Clinical manifestations of DCM are mainly the symptoms of heart failure; it is diagnosed by EKG, chest x-ray and echocardiography. For the idiopathic and familial diseases cases of DCM, there are no definite guidelines for treatment in children as they are treated for prognostic improvement.

CASE PRESENTATION

We report the case of a 2-year-old girl diagnosed with dilated cardiomyopathy associated with homozygous mutation in the Myosin Light Chain 3 gene admitted for edema in lower extremities, muscle weakness, lethargy and vomiting, and she was found to be in cardiogenic shock. Chest x-ray showed cardiomegaly and EKG showed first degree atrioventricular block. Echocardiogram showed severe biventricular systolic and diastolic dysfunction. After 70 days of hospitalization, the patient went into cardiac arrest with cessation of electrical and mechanical activity of the heart, despite cardiopulmonary resuscitative efforts.

CONCLUSION

Although rare, pediatric DCM carries a high risk of morbidity and mortality and a lack of curative therapy.

Titin: The Missing Link in Cardiac Physiology

Titin, an extraordinary protein known for its colossal size and multifaceted roles, is a cornerstone in the structural and functional dynamics of striated muscle tissues, including the heart and skeletal muscles. Its sheer enormity, with a molecular weight exceeding 3000 kDa, is paralleled only by the immense influence it exerts on muscle physiology. This review will delve into the remarkable structural organization of Titin and the genetics of this molecule, including the common mutations resulting in various cardiomyopathies. We will delve deeper into its role in dilated cardiomyopathy, familial restrictive cardiomyopathy, hypertrophic cardiomyopathy, and left ventricular noncompaction cardiomyopathy. This review culminates by discussing the prospects of therapeutic strategies targeting Titin. While these interventions remain primarily theoretical, the possibilities are intriguing. Patients with Titin truncation mutations present unique challenges, but innovative approaches like gene therapy or preemptive treatments with drugs such as angiotensin-converting enzyme inhibitors or beta-blockers offer hope. This multi-pronged approach highlights the significance of understanding Titin's multifaceted role and its potential as a target for future therapeutic interventions.

Heart in Disguise: Unmasking a Novel Gene Deletion in Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is an underrecognized condition with a myriad of etiologies, but it is often labeled idiopathic. However, genetic mutations are emerging as a more common cause of idiopathic DCM than previously believed. Herein, we present a case of a previously healthy 45-year-old woman who presented with three weeks of exertional dyspnea and orthopnea. An echocardiogram showed DCM with severely reduced systolic function and diastolic dysfunction. She was extensively worked up for potential etiologies of her heart failure which included HIV testing, parasite smear, viral serologies, autoimmune testing, cardiac MRI for infiltrative diseases, and coronary catheterization. She was ultimately tested for genetic mutations which revealed a 49-51 exon deletion of the dystrophin (Duchenne muscular dystrophy (DMD)) gene. This case highlights the guideline-based evaluation and management of new-onset heart failure in a healthy 45-year-old female without known predisposing risk factors or family history. It also sheds light on the expansive genetic etiologies that have only recently been identified in those with idiopathic cardiomyopathy. Further research is crucial to improve our understanding of genetic associations of cardiomyopathy.

A novel combination of filamin C mutation and cardiorespiratory sarcoidosis in a patient with left ventricular systolic dysfunction

Cardiac sarcoidosis is an unpredictable, rare and potentially lethal condition whereby patients are exposed to sudden cardiac death. However, despite sophisticated imaging techniques and the need for careful multidisciplinary team assessment and management, the contribution from genetic mutations is uncertain. Hence, the case describes a novel observation of a patient who possessed both a filamin C mutation and cardiac sarcoidosis. The case highlights the need for detailed dedicated investigation and highlights the need for the consideration of genetic screening within patients with cardiac sarcoidosis.

LMNA Cardiomyopathy: Important Considerations for the Heart Failure Clinician

BACKGROUND

A diagnosis of Lamin proteins A and C cardiomyopathy (LMNA-CM) not only impacts disease prognosis, but also leads to specific guideline-recommended treatment options for these patients. This etiology is fundamentally different from other genetic causes of dilated CM.

METHODS AND RESULTS

LMNA-CM often presents early in the third to fourth decades and there is an age-dependent penetrance of nearly 90% among those with a positive genotype for LMNA-CM. Oftentimes, electrical abnormalities with either conduction disturbances and/or either atrial or ventricular arrhythmias manifest before there is imaging evidence of left ventricular dysfunction. Given these subtle early findings, cardiac magnetic resonance provides helpful guidance regarding patterns of enhancement associated with LMNA-CM, often before there is significant left ventricular dilation and/or a decrease in the ejection fraction and could be used for further understanding of risk stratification and prognosis of asymptomatic genotype-positive individuals. Among symptomatic patients with LMNA-CM, approximately one-quarter of individuals progress to needing advanced heart failure therapies such as heart transplantation.

CONCLUSIONS

In the era of precision medicine, increased recognition of clinical findings associated with LMNA-CM and increased detection by genetic testing among patients with idiopathic nonischemic CM is of increasing importance. Not only does a diagnosis of LMNA-CM have implications for management and risk stratification, but new gene-based therapies continue to be evaluated for this group. Clinicians must be aware not only of the general indications for genetic testing in arrhythmogenic and dilated cardiomyopathies and of when to suspect LMNA-CM, but also of the clinical trials underway targeted toward the different genetic cardiomyopathies.

Case report: A new de novo mutation of the Troponin T2 gene in a Chinese patient with dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a cardiovascular disease characterized by persistent ventricular dilatation and systolic dysfunction. DCM has a variety of causes, including myocarditis; exposure to narcotics, alcohol, or other toxins; and metabolic or endocrine disorders. Genetic factors play a dominant role in 30%-40% of DCM cases. Here, we report a case of DCM with very severe heart failure. Because of the severity of heart failure, the patient underwent heart transplantation. We speculated that the patient's DCM might be due to a mutation; hence, we performed whole-exome sequencing of the patient and their parents, which showed a de novo heterozygous mutation (NM_001001431.2c.769G>A:p.E257K) in TNNT2, which was considered pathogenic according to the ACMG pathogenicity assessment. This finding expands the genetic map of DCM and TNNT2 and will be important for future studies on the genetic and disease relationships between DCM and TNNT2.

Genetic heterogeneity of cardiomyopathy and its correlation with patient care

BACKGROUND

Cardiomyopathy, which is a genetically and phenotypically heterogeneous pathological condition, is associated with increased morbidity and mortality. Genetic diagnosis of cardiomyopathy enables accurate phenotypic classification and optimum patient management and counseling. This study investigated the genetic spectrum of cardiomyopathy and its correlation with the clinical course of the disease.

METHODS

The samples of 72 Korean patients with cardiomyopathy (43 males and 29 females) were subjected to whole-exome sequencing (WES). The familial information and clinical characteristics of the patients were reviewed and analyzed according to their genotypes.

RESULTS

Dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), left ventricular non-compaction cardiomyopathy, and restrictive cardiomyopathy was detected in 41 (56.9%), 25 (34.7%), 4 (5.6%), and 2 (2.8%) patients, respectively. WES analysis revealed positive results in 37 (51.4%) patients. Subsequent familial testing identified ten additional familial cases. Among DCM cases, 19 (46.3%) patients exhibited positive results, with TTN variants being the most common alteration, followed by LMNA and MYH7 variants. Meanwhile, among HCM cases, 15 (60%) patients exhibited positive results with MYH7 variants being the most common alteration. In six patients with positive results, extracardiac surveillance was warranted based on disease information. The incidence of worse outcomes, such as mortality and life-threatening arrhythmic events, in patients with DCM harboring LMNA variants, was higher than that in patients with DCM harboring TTN or MYH7 variants.

CONCLUSIONS

Diverse genotypes were identified in a substantial proportion of patients with cardiomyopathy. Genetic diagnosis enables personalized disease surveillance and management.

Novel pathogenic variant in LMNA gene identified in a six-generation family causing atrial cardiomyopathy and associated right atrial conduction arrhythmias

Objective

To characterize the cardiac phenotype associated with the novel pathogenic variant (c.1526del) of LMNA gene, which we identified in a large, six-generation family.

Methods and Results

A family tree was constructed. The clinical data of living and deceased family members were collected. DNA samples from 7 family members were analyzed for LMNA mutations using whole-exome high-throughput sequencing technology. The clinical presentation of pathogenic variant carriers was evaluated. In this six-generation family (n = 67), one member experienced sudden death at the age of 40-years-old. Three pathogenic variant carriers were identified to possess a novel heterozygous deletion mutation in LMNA gene (HGVS: NM_170707.4, c.1526del) located at exon 9 of LMNA chr1:156137145, which creates a premature translational stop signal (p.Pro509Leufs*39) in the LMNA gene and results in an mutant lamin A protein product. The main symptoms of the pathogenic variant carriers were palpitation, fatigue, and syncope, which typically occurred around 20-years-old. AV-conduction block and non-sustained ventricular tachycardia were the first signs of disease and would rapidly progress to atrial standstill around 30-years-old. Significant right atrial enlargement and bicuspid aortic valve malformation was also commonly seen in patients who carried this pathogenic variant.

Conclusion

The pathogenic variant of c.1526del p.P509Lfs*39 was a frameshift deletion located at exon 9 of LMNA chr1:156137145 and causes severe right atrial enlargement, sick sinus syndrome, atrial standstill, ventricular tachycardia, and bicuspid aortic valve malformation. Our findings expand the phenotypic spectrum of novel LMNA gene mutations.

Sudden cardiac death in the young: A consensus statement on recommended practices for cardiac examination by pathologists from the Society for Cardiovascular Pathology

Sudden cardiac death is, by definition, an unexpected, untimely death caused by a cardiac condition in a person with known or unknown heart disease. This major international public health problem accounts for approximately 15-20% of all deaths. Typically more common in older adults with acquired heart disease, SCD also can occur in the young where the cause is more likely to be a genetically transmitted process. As these inherited disease processes can affect multiple family members, it is critical that these deaths are appropriately and thoroughly investigated. Across the United States, SCD cases in those less than 40 years of age will often fall under medical examiner/coroner jurisdiction resulting in scene investigation, review of available medical records and a complete autopsy including toxicological and histological studies. To date, there have not been consistent or uniform guidelines for cardiac examination in these cases. In addition, many medical examiner/coroner offices are understaffed and/or underfunded, both of which may hamper specialized examinations or studies (e.g., molecular testing). Use of such guidelines by pathologists in cases of SCD in decedents aged 1-39 years of age could result in life-saving medical intervention for other family members. These recommendations also may provide support for underfunded offices to argue for the significance of this specialized testing. As cardiac examinations in the setting of SCD in the young fall under ME/C jurisdiction, this consensus paper has been developed with members of the Society of Cardiovascular Pathology working with cardiovascular pathology-trained, practicing forensic pathologists.

Development of Dilated Cardiomyopathy in a Young Woman After Bilateral Cardiac Sympathetic Denervation in Catecholaminergic Polymorphic Ventricular Tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) can cause fatal tachyarrhythmias brought on by physical or emotional stress. Previously published cases deny the association between CPVT with dilated cardiomyopathy (DCM). However, rare cases show a possible association between CPVT and DCM development. Our case is one of them; we describe the development of dilated cardiomyopathy in a young woman who, six years earlier, went through bilateral cardiac sympathetic denervation (CSD) because of symptomatic catecholaminergic polymorphic ventricular tachycardia.

The Role of MicroRNAs in Dilated Cardiomyopathy: New Insights for an Old Entity

Dilated cardiomyopathy (DCM) is a clinical diagnosis characterized by left ventricular or biventricular dilation and systolic dysfunction. In most cases, DCM is progressive, leading to heart failure (HF) and death. This cardiomyopathy has been considered a common and final phenotype of several entities. DCM occurs when cellular pathways fail to maintain the pumping function. The etiology of this disease encompasses several factors, such as ischemia, infection, autoimmunity, drugs or genetic susceptibility. Although the prognosis has improved in the last few years due to red flag clinical follow-up, early familial diagnosis and ongoing optimization of treatment, due to its heterogeneity, there are no targeted therapies available for DCM based on each etiology. Therefore, a better understanding of the mechanisms underlying the pathophysiology of DCM will provide novel therapeutic strategies against this cardiac disease and their different triggers. MicroRNAs (miRNAs) are a group of small noncoding RNAs that play key roles in post-transcriptional gene silencing by targeting mRNAs for translational repression or, to a lesser extent, degradation. A growing number of studies have demonstrated critical functions of miRNAs in cardiovascular diseases (CVDs), including DCM, by regulating mechanisms that contribute to the progression of the disease. Herein, we summarize the role of miRNAs in inflammation, endoplasmic reticulum (ER) stress, oxidative stress, mitochondrial dysfunction, autophagy, cardiomyocyte apoptosis and fibrosis, exclusively in the context of DCM.

Genomic findings of hypertrophic and dilated cardiomyopathy characterized in a Thai clinical genetics service

Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are the most common referrals in the Inherited Cardiovascular Condition (ICC) Genetics Service. Several issues must be discussed with patients and their families during the genetic consultation session, including the options for genetic testing and cardiovascular surveillance in family members. We developed an ICC registry and performed next-generation-based DNA sequencing for all patients affected by non-syndromic HCM and idiopathic DCM in our joint specialist genetics service. The target gene sequencing panel relied on the Human Phenotype Ontology with 237 genes for HCM (HP:0001639) and 142 genes for DCM (HP:0001644). All subjects were asked to contact their asymptomatic first-degree relatives for genetic counseling regarding their risks and to initiate cardiovascular surveillance and cascade genetic testing. The study was performed from January 1, 2014, to December 31, 2020, and a total of 62 subjects (31-HCM and 31-DCM) were enrolled. The molecular detection frequency was 48.39% (32.26% pathogenic/likely pathogenic, 16.13% variant of uncertain significance or VUS for HCM, and 25.81% (16.13% pathogenic/likely pathogenic, 9.68% VUS) for DCM. The most prevalent gene associated with HCM was MYBPC3. The others identified in this study included ACTN2, MYL2, MYH7, TNNI3, TPM1, and VCL. Among the DCM subjects, variants were detected in two cases with the TTN nonsense variants, while the others were missense and identified in MYH7, DRSP3, MYBPC3, and SCN5A. Following the echocardiogram surveillance and cascade genetic testing in the asymptomatic first-degree relatives, the detection rate of new cases was 8.82% and 6.25% in relatives of HCM and DCM subjects, respectively. Additionally, a new pre-symptomatic relative belonging to an HCM family was identified, although the genomic finding in the affected case was absent. Thus, ICC service is promising for the national healthcare system, aiming to prevent morbidity and mortality in asymptomatic family members.

Identification and functional characterization of BICD2 as a candidate disease gene in an consanguineous family with dilated cardiomyopathy

Background

Familial dilated cardiomyopathy (DCM) is a genetic cardiomyopathy that is associated with reduced left ventricle function or systolic function. Fifty-one DCM-causative genes have been reported, most of which are inherited in an autosomal dominant manner. However, recessive DCM-causative gene is rarely observed.

Methods

Whole-exome sequencing (WES) was performed in a consanguineous family with DCM to identify candidate variants. Sanger sequencing was utilized to confirm the variant. We then checked the DCM candidate gene in 210 sporadic DCM cases. We next explored BICD2 function in both embryonic and adult bicd2-knockout zebrafish models. In vivo cardiac function of bicd2-knockout fish was detected by echocardiography and RNA-seq.

Results

We identified an autosomal recessive and evolutionarily conserved missense variant, NM_001003800.1:c.2429G > A, in BICD2, which segregated with the disease phenotype in a consanguineous family with DCM. Furthermore, we confirmed the presence of BICD2 variants in 3 sporadic cases. Knockout of bicd2 resulted in partial embryonic lethality in homozygotes, suggesting a vital role for bicd2 in embryogenesis. Heart dilation and decreased ejection fraction, cardiac output and stroke volume were observed in bicd2-knockout zebrafish, suggesting a phenotype similar to human DCM. Furthermore, RNA-seq confirmed a larger transcriptome shift in in bicd2 homozygotes than in heterozygotes. Gene set enrichment analysis of bicd2-deficient fish showed the enrichment of altered gene expression in cardiac pathways and mitochondrial energy metabolism.

Conclusions

Our study first shows that BICD2 is a novel candidate gene associated with familial DCM, and our findings will facilitate further insights into the molecular pathological mechanisms of DCM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01349-y.

Genetic Association of Beta-Myosin Heavy-Chain Gene (MYH7) with Cardiac Dysfunction

Cardiac dysfunction accelerates the risk of heart failure, and its pathogenesis involves a complex interaction between genetic and environmental factors. Variations in myosin affect contractile abilities of cardiomyocytes and cause structural and functional abnormalities in myocardium. The study aims to find the association of MYH7 rs121913642 (c.1594 T>C) and rs121913645 (c.667G>A) variants with cardiac dysfunction in the Punjabi Pakistani population. Patients with heart failure (n = 232) and healthy controls (n = 205) were enrolled in this study. MYH7 variant genotyping was performed using tetra ARMS-PCR. MYH7 rs121913642 TC genotype was significantly more prevalent in the patient group (p < 0.001). However, MYH7 rs121913645 genotype frequencies were not significantly different between the patient and control groups (p < 0.666). Regression analysis also revealed that the rs121913642 C allele increases the risk of cardiac failure by ~2 [OR:1.98, CI: 1.31−2.98, p < 0.001] in comparison to the T allele. High levels of the cardiac enzymes cardiac troponin I (cTnI) and CK-MB were observed in patients. There was also an increase in total cholesterol, LDL cholesterol, and uric acid in patients compared to the healthy control group (p < 0.001). In conclusion, the MYH7 gene variant rs121913642 is genetically associated with cardiac dysfunction and involved in the pathogenesis of HF.

Personalized Medicine Approach in a DCM Patient with LMNA Mutation Reveals Dysregulation of mTOR Signaling

Background: Mutations in the Lamin A/C (LMNA) gene are responsible for about 6% of all familial dilated cardiomyopathy (DCM) cases which tend to present at a young age and follow a fulminant course. Methods: We report a 47-year-old DCM patient with severely impaired left ventricular ejection fraction and NYHA functional class IV despite optimal heart failure treatment. Whole-exome sequencing revealed an LMNA E161K missense mutation as the pathogenetic cause for DCM in this patient. We generated a patient-specific LMNA-knock in (LMNA-KI) in vitro model using mES cells. Results: Beta adrenergic stimulation of cardiomyocytes derived from LMNA-KI mES cells resulted in augmented mTOR signaling and increased dysregulation of action potentials, which could be effectively prevented by the mTOR-inhibitor rapamycin. A cardiac biopsy confirmed strong activation of the mTOR-signaling pathway in the patient. An off-label treatment with oral rapamycin was initiated and resulted in an improvement in left ventricular ejection fraction (27.8% to 44.5%), NT-BNP (8120 ng/L to 2210 ng/L) and NYHA functional class. Conclusion: We have successfully generated the first in vitro model to recapitulate a patient-specific LMNA E161K mutation which leads to a severe form of DCM. The model may serve as a template for individualized and specific treatment of heart failure.

Unfolding the genotype-to-phenotype black box of cardiovascular diseases through cross-scale modeling

Complex traits such as cardiovascular diseases (CVD) are the results of complicated processes jointly affected by genetic and environmental factors. Genome-wide association studies (GWAS) identified genetic variants associated with diseases but usually did not reveal the underlying mechanisms. There could be many intermediate steps at epigenetic, transcriptomic, and cellular scales inside the black box of genotype-phenotype associations. In this article, we present a machine-learning-based cross-scale framework GRPath to decipher putative causal paths (pcPaths) from genetic variants to disease phenotypes by integrating multiple omics data. Applying GRPath on CVD, we identified 646 and 549 pcPaths linking putative causal regions, variants, and gene expressions in specific cell types for two types of heart failure, respectively. The findings suggest new understandings of coronary heart disease. Our work promoted the modeling of tissue- and cell type-specific cross-scale regulation to uncover mechanisms behind disease-associated variants, and provided new findings on the molecular mechanisms of CVD.

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We defined one type of cross-scale genotype-to-phenotype regulation path

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We designed a framework GRPath to uncover putative regulation paths for diseases

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GRPath helped uncover molecular mechanisms for two major types of heart failure

Transcriptome analysis uncovers the autophagy-mediated regulatory patterns of the immune microenvironment in dilated cardiomyopathy

The relationship between autophagy and immunity has been well studied. However, little is known about the role of autophagy in the immune microenvironment during the progression of dilated cardiomyopathy (DCM). Therefore, this study aims to uncover the effect of autophagy on the immune microenvironment in the context of DCM. By investigating the autophagy gene expression differences between healthy donors and DCM samples, 23 dysregulated autophagy genes were identified. Using a series of bioinformatics methods, 13 DCM‐related autophagy genes were screened and used to construct a risk prediction model, which can well distinguish DCM and healthy samples. Then, the connections between autophagy and immune responses including infiltrated immunocytes, immune reaction gene‐sets and human leukocyte antigen (HLA) genes were systematically evaluated. In addition, two autophagy‐mediated expression patterns in DCM were determined via the unsupervised consensus clustering analysis, and the immune characteristics of different patterns were revealed. In conclusion, our study revealed the strong effect of autophagy on the DCM immune microenvironment and provided new insights to understand the pathogenesis and treatment of DCM.

Dilated cardiomyopathy caused by a pathogenic nucleotide variant in RBM20 in an Iranian family

Introduction

Dilated cardiomyopathy (DCM) is characterized by the dilation and impaired contraction of 1 or both ventricles and can be caused by a variety of disorders. Up to 50% of idiopathic DCM cases have heritable familial diseases, and the clinical screening of family members is recommended. Identifying a genetic cause that can explain the DCM risk in the family can help with better screening planning and clinical decision-making. Whole-exome sequencing (WES) has aided significantly in the detection of causative genes in many genetically heterogeneous diseases. In the present study, we applied WES to identify the causative genetic variant in a family with heritable DCM.

Methods

WES was applied to identify genetic variants on a 26-year-old man as the proband of a family with DCM. Subsequently, Sanger sequencing was performed to confirm the variant in the patient and all the available affected and unaffected family members. The pathogenicity of the variant was evaluated through co-segregation analysis in the family and employment of in silico predictive software.

Results

WES demonstrated the missense pathogenic heterozygous nucleotide variant, c.1907G > A, (p.Arg636His, rs267607004, NM_0011343), in exon 9 of the RBM20 gene in the proband. The variant was co-segregated in all the affected family members in a heterozygous form and the unaffected family members. The in silico analysis confirmed the variant as pathogenic.

Conclusion

Pathogenic RBM20 nucleotide variants are associated with arrhythmogenic DCM. We believe that our report is the first to show an RBM20 variant in Iranian descent associated with DCM.

Metabolomics Fingerprint Predicts Risk of Death in Dilated Cardiomyopathy and Heart Failure

Background

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. Metabolomics may help refine risk assessment and potentially guide HF management, but dedicated studies are few. This study aims at stratifying the long-term risk of death in a cohort of patients affected by HF due to dilated cardiomyopathy (DCM) using serum metabolomics via nuclear magnetic resonance (NMR) spectroscopy.

Methods

A cohort of 106 patients with HF due to DCM, diagnosed and monitored between 1982 and 2011, were consecutively enrolled between 2010 and 2012, and a serum sample was collected from each participant. Each patient underwent half-yearly clinical assessments, and survival status at the last follow-up visit in 2019 was recorded. The NMR serum metabolomic profiles were retrospectively analyzed to evaluate the patient's risk of death. Overall, 26 patients died during the 8-years of the study.

Results

The metabolomic fingerprint at enrollment was powerful in discriminating patients who died (HR 5.71, p = 0.00002), even when adjusted for potential covariates. The outcome prediction of metabolomics surpassed that of N-terminal pro b-type natriuretic peptide (NT-proBNP) (HR 2.97, p = 0.005). Metabolomic fingerprinting was able to sub-stratify the risk of death in patients with both preserved/mid-range and reduced ejection fraction [hazard ratio (HR) 3.46, p = 0.03; HR 6.01, p = 0.004, respectively]. Metabolomics and left ventricular ejection fraction (LVEF), combined in a score, proved to be synergistic in predicting survival (HR 8.09, p = 0.0000004).

Conclusions

Metabolomic analysis via NMR enables fast and reproducible characterization of the serum metabolic fingerprint associated with poor prognosis in the HF setting. Our data suggest the importance of integrating several risk parameters to early identify HF patients at high-risk of poor outcomes.

Teen pregnancy in the setting of familial dilated cardiomyopathy: a case report

Background

Women with pre-existing forms of familial cardiomyopathy are at increased risk for morbidity and mortality due to hemodynamic changes of pregnancy. There is a lack of consensus about the management and care for these patients given the rarity of this condition. This case represents possibly the youngest pregnant familial dilated cardiomyopathy patient to deliver and the youngest patient to be fitted for a wearable cardiac defibrillator in the postpartum period.

Case Presentation

A 14-year-old gravida 1 with familial dilated cardiomyopathy presented late for prenatal care at 38 weeks, which precluded typical care plans including baseline and serial echocardiograms, medication management, and routine prenatal care. An echocardiogram showed severely decreased left ventricular systolic function compared to studies from one year prior. Three days later the patient presented in labor and had a spontaneous vaginal delivery complicated by postpartum hemorrhage. Her postpartum course was notable for persistence of decreased cardiac function testing and placement of a wearable cardiac defibrillator for prevention against life threatening arrhythmias.

Conclusion

This case report adds to the literature on pregnancy complicated by familial dilated cardiomyopathy and describes management best practices and considerations during the antepartum, intrapartum, and postpartum periods.

Clinical Implication of Genetic Testing in Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is one of the important causes of heart failure (HF). With the rapidly evolving technologies for gene analysis and tremendous advances in knowledge of HF genetics, the importance of genetic testing in DCM is currently highlighted. Several genetic variants causing DCM have been identified and this information is used for diagnosis, risk stratification and family screening of DCM patients. However, there are still several challenges in applying genetic testing to real clinical practice. In this review, we will summarize recent understandings in DCM genetics and provide an evidence-based practical guide to the use of genetic testing for DCM patients.

Artificial Intelligence-Enabled Electrocardiography to Screen Patients with Dilated Cardiomyopathy

Undiagnosed dilated cardiomyopathy (DC) can be asymptomatic or present as sudden cardiac death, therefore pre-emptively identifying and treating patients may be beneficial. Screening for DC with echocardiography is expensive and labor intensive and standard electrocardiography (ECG) is insensitive and non-specific. The performance and applicability of artificial intelligence-enabled electrocardiography (AI-ECG) for detection of DC is unknown. Diagnostic performance of an AI algorithm in determining reduced left ventricular ejection fraction (LVEF) was evaluated in a cohort that comprised of DC and normal LVEF control patients. DC patients and controls with 12-lead ECGs and a reference LVEF measured by echocardiography performed within 30 and 180 days of the ECG respectively were enrolled. The model was tested for its sensitivity, specificity, negative predictive (NPV) and positive predictive values (PPV) based on the prevalence of DC at 1% and 5%. The cohort consisted of 421 DC cases (60% males, 57±15 years, LVEF 28±11%) and 16,025 controls (49% males, age 69 ±16 years, LVEF 62±5%). For detection of LVEF≤45%, the area under the curve (AUC) was 0.955 with a sensitivity of 98.8% and specificity 44.8%. The NPV and PPV were 100% and 1.8% at a DC prevalence of 1% and 99.9% and 8.6% at a prevalence of 5%, respectively. In conclusion AI-ECG demonstrated high sensitivity and negative predictive value for detection of DC and could be used as a simple and cost-effective screening tool with implications for screening first degree relatives of DC patients.

Interpretation of Incidental Genetic Findings Localizing to Genes Associated With Cardiac Channelopathies and Cardiomyopathies

Recent advances in next-genetic sequencing technology have facilitated an expansion in the use of exome and genome sequencing in the research and clinical settings. While this has aided in the genetic diagnosis of individuals with atypical clinical presentations, there has been a marked increase in the number of incidentally identified variants of uncertain diagnostic significance in genes identified as clinically actionable by the American College of Medical Genetics guidelines. Approximately 20 of these genes are associated with cardiac diseases, which carry a significant risk of sudden cardiac death. While identification of at-risk individuals is paramount, increased discovery of incidental variants of uncertain diagnostic significance has placed a burden on the clinician tasked with determining the diagnostic significance of these findings. Herein, we describe the scope of this emerging problem using cardiovascular genetics to illustrate the challenges associated with variants of uncertain diagnostic significance interpretation. We review the evidence for diagnostic weight of these variants, discuss the role of clinical genetics providers in patient care, and put forward general recommendations about the interpretation of incidentally identified variants found with clinical genetic testing.

The Complex and Diverse Genetic Architecture of Dilated Cardiomyopathy

Our insight into the diverse and complex nature of dilated cardiomyopathy (DCM) genetic architecture continues to evolve rapidly. The foundations of DCM genetics rest on marked locus and allelic heterogeneity. While DCM exhibits a Mendelian, monogenic architecture in some families, preliminary data from our studies and others suggests that at least 20% to 30% of DCM may have an oligogenic basis, meaning that multiple rare variants from different, unlinked loci, determine the DCM phenotype. It is also likely that low-frequency and common genetic variation contribute to DCM complexity, but neither has been examined within a rare variant context. Other types of genetic variation are also likely relevant for DCM, along with gene-by-environment interaction, now established for alcohol- and chemotherapy-related DCM. Collectively, this suggests that the genetic architecture of DCM is broader in scope and more complex than previously understood. All of this elevates the impact of DCM genetics research, as greater insight into the causes of DCM can lead to interventions to mitigate or even prevent it and thus avoid the morbid and mortal scourge of human heart failure.

Heterozygous desmin gene (DES) mutation contributes to familial dilated cardiomyopathy

Familial dilated cardiomyopathy (FDCM) is characterized by high genetic heterogeneity and an increased risk of heart failure or sudden cardiac death in adults. We report the case of a 62-year-old man with a 2-month history of shortness of breath during activity, without paroxysmal nocturnal dyspnea. The patient underwent a series of examinations including transthoracic echocardiography, coronary arteriography, transesophageal echocardiography, and myocardial perfusion imaging. After excluding secondary cardiac enlargement, he was diagnosed with dilated cardiomyopathy (DCM). His sister had also been diagnosed with DCM several years before. Genetic sequencing analysis revealed that the patient, his sister, and his son all had the same mutation in the desmin gene (DES) (chr2-220785662, c.1010C>T). Genetic testing confirmed a heterozygous DES mutation contributing to FDCM. In this case, the etiology of the patient’s whole-heart enlargement was determined as FDCM with DES gene mutation. This is the first report to describe DES c.1010C>T as a cause of FDCM.

Timing of pacemaker and ICD implantation in LMNA mutation carriers

AIMS

LMNA-cardiomyopathy is often associated with pathology in the cardiac conduction system necessitating device implantations. The aim was to study the timing and types of device implantations and need for re-implantations in LMNA mutation carriers.

METHODS

We studied the hospital records of 60 LMNA mutation carriers concerning device implantations and re-implantations and their indications. Data were collected until April 2019.

RESULTS

The median follow-up time from the first ECG recording to the last clinical follow-up, transplantation, or death was 7.7 (IQR=9.1) years. Altogether 61.7% (n=37) of the LMNA mutation carriers received a pacemaker or an implantable cardioverter defibrillator (ICD), and of them 27.0% (n=10) needed a device upgrade. Notably, in some patients the upgrade took place very soon after the first implantation. The first device was implanted at an average age of 47.9 years (SD=9.5), whereas the upgrade took place at an average age of 50.3 years (SD=8.1). Most upgrades were ICD implantations. Male patients underwent device upgrade more often and at a younger age than women. By the end of follow-up, 35.0% (n=21) of the patients fulfilled echocardiographic criteria for dilated cardiomyopathy, and 90.5% of them (n=19) needed pacemaker implantation.

CONCLUSION

Most LMNA mutation carriers underwent pacemaker implantation in this study. Due to the progressive nature of LMNA-cardiomyopathy, device upgrades are quite common. An ICD should be considered when the initial device implantation is planned in an LMNA mutation carrier.

Clinical Characteristics and Contemporary Management of Patients With Cardiomyopathies in Japan - Report From a National Registry of Clinical Personal Records

Background: The clinical features of patients with cardiomyopathy, including dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), or restrictive cardiomyopathy (RCM), have not been recently elucidated in Japan.

Methods and Results: We collected individual patient data regarding demographics, echocardiogram, and treatment in DCM from 2003 to 2014 and in HCM and RCM from 2009 to 2014 from the national registry of clinical personal records organized by the Japanese Ministry of Health, Labour and Welfare. In all, 44,136 patients were included in this registry: 40,537 with DCM, 3,553 with HCM, and 46 with RCM. The median age at diagnosis was older for DCM and HCM than RCM (54 and 55 vs. 42 years, respectively). Male patients accounted for 74.6%, 58.7%, and 60.9% of the DCM, HCM, and RCM groups, respectively. NYHA functional Class III–IV was found in 26.9%, 11.3%, and 58.1% of patients in the DCM, HCM, and RCM groups, respectively. In the DCM group, the rates of β-blocker and angiotensin-converting enzyme inhibitor/angiotensin receptor blocker prescription were 69% and 76%, respectively. In regional subgroup analysis, the median age at diagnosis of DCM and HCM was younger in the Kanto region. A family history of HCM was less frequent in the Hokkaido/Tohoku region.

Conclusions: The national registry of clinical personal records of cardiomyopathy could provide important information regarding the demographics, clinical characteristics, and management of cardiomyopathy throughout Japan.

LncRNA ZNF593-AS Alleviates Contractile Dysfunction in Dilated Cardiomyopathy

[Figure: see text].

Genetic Restrictive Cardiomyopathy: Causes and Consequences-An Integrative Approach

The sarcomere as the smallest contractile unit is prone to alterations in its functional, structural and associated proteins. Sarcomeric dysfunction leads to heart failure or cardiomyopathies like hypertrophic (HCM) or restrictive cardiomyopathy (RCM) etc. Genetic based RCM, a very rare but severe disease with a high mortality rate, might be induced by mutations in genes of non-sarcomeric, sarcomeric and sarcomere associated proteins. In this review, we discuss the functional effects in correlation to the phenotype and present an integrated model for the development of genetic RCM.

Differential Expression Profiles and Functional Analysis of Long Non-coding RNAs in Children With Dilated Cardiomyopathy

Aim: To evaluate the expression profile of long non-coding RNAs (lncRNAs) in different left ventricular function of dilated cardiomyopathy (DCM) in children and explore their possible functions. Methods: The lncRNA microarray experiment was used to determine the differential expression profile of lncRNA in three children with DCM and three healthy volunteers. The functional analysis and the construction of the lncRNA-mRNA interaction network were carried out to study the biological functions. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis was used to verify the microarray data. Results: There were 369 up-regulated lncRNAs identified in the DCM patients (fold change >2, P < 0.05), and 505 down-regulated lncRNAs. Based on target gene prediction and co-expression network construction, 9 differentially expressed lncRNAs were selected for the PCR to verify the accuracy of the microarray data, of which 5 were up-regulated and 4 were down-regulated, and finally proved that 7 of them were consistent with the trend of microarray data results. Four of these lncRNAs had significant differences between the patients with poor cardiac function and patients with improved left ventricle function. Conclusion: LncRNAs may play an important role in pediatric DCM and may provide a new perspective for the pathogenesis, diagnosis, and treatment of this disease.

Considering complexity in the genetic evaluation of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a cardiovascular disease of genetic aetiology that causes substantial morbidity and mortality, and presents considerable opportunity for disease mitigation and prevention in those at risk. Foundational to the process of caring for patients diagnosed with DCM is a clinical genetic evaluation, which always begins with a comprehensive family history and clinical evaluation. Genetic testing of the proband, the first patient identified in a family with DCM, within the context of genetic counselling is always indicated, regardless of whether the DCM is familial or non-familial. Clinical screening of at-risk family members is also indicated, as is cascade genetic testing for actionable variants found at genetic testing in the proband. Clinicians now have expansive panels with many genes available for DCM genetic testing, and the approaches used to evaluate rare variants to decide which are disease-causing continues to rapidly evolve. Despite these recent advances, only a minority of cases yield actionable variants, even in familial DCM where a genetic aetiology is highly likely. This underscores that our knowledge of DCM clinical genetics remains incomplete, including variant interpretation and DCM genetic architecture. Emerging data suggest that the single-variant Mendelian disease model is insufficient to explain some DCM cases, and rather that multiple variants, both common and rare, and at times key environmental factors, interact to cause DCM. A simple model illustrating the intersection of DCM genetic architecture with environmental impact is provided.

Drug Development and the Use of Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Disease Modeling and Drug Toxicity Screening

: Over the years, numerous groups have employed human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) as a superb human-compatible model for investigating the function and dysfunction of cardiomyocytes, drug screening and toxicity, disease modeling and for the development of novel drugs for heart diseases. In this review, we discuss the broad use of iPSC-CMs for drug development and disease modeling, in two related themes. In the first theme-drug development, adverse drug reactions, mechanisms of cardiotoxicity and the need for efficient drug screening protocols-we discuss the critical need to screen old and new drugs, the process of drug development, marketing and Adverse Drug reactions (ADRs), drug-induced cardiotoxicity, safety screening during drug development, drug development and patient-specific effect and different mechanisms of ADRs. In the second theme-using iPSC-CMs for disease modeling and developing novel drugs for heart diseases-we discuss the rationale for using iPSC-CMs and modeling acquired and inherited heart diseases with iPSC-CMs.

A Novel Recessive Mutation in SPEG Causes Early Onset Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is a common cause of heart failure and sudden cardiac death. It has been estimated that up to half of DCM cases are hereditary. Mutations in more than 50 genes, primarily autosomal dominant, have been reported. Although rare, recessive mutations are thought to contribute considerably to DCM, especially in young children. Here we identified a novel recessive mutation in the striated muscle enriched protein kinase (SPEG, p. E1680K) gene in a family with nonsyndromic, early onset DCM. To ascertain the pathogenicity of this mutation, we generated SPEG E1680K homozygous mutant human induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) using CRISPR/Cas9-mediated genome editing. Functional studies in mutant iPSC-CMs showed aberrant calcium homeostasis, impaired contractility, and sarcomeric disorganization, recapitulating the hallmarks of DCM. By combining genetic analysis with human iPSCs, genome editing, and functional assays, we identified SPEG E1680K as a novel mutation associated with early onset DCM and provide evidence for its pathogenicity in vitro. Our study provides a conceptual paradigm for establishing genotype-phenotype associations in DCM with autosomal recessive inheritance.

Clinicogenetical Variants of Progressive External Ophthalmoplegia - An Especial Review of Non-ophthalmic Manifestations

Progressive external ophthalmoplegia (PEO) is a slowly progressive myopathy characterized by extraocular muscles involvement, leading to frozen eyes without diplopia. The pattern of inheritance may be mitochondrial, autosomal dominant or, rarely, autosomal recessive. Sporadic forms were also reported. Muscular involvement other than extraocular muscles may occur with varying degrees of weakness, but this mostly happens many years after the disease begins. There are also scattered data about systemic signs besides ophthalmoplegia. This article aims to review non-ophthalmic findings of PEO from a clinicogenetical point of view.

Clinical utility of genetic testing in patients with dilated cardiomyopathy

INTRODUCTION AND OBJECTIVES

Dilated cardiomyopathy (DCM) is the most frequent cause of heart transplantation. The prevalence of familial disease can reach 50%. Our objective was to describe the genetic basis of DCM in a cohort with a high proportion of transplanted patients.

METHODS

We included patients with DCM and genetic testing performed using next-generation sequencing (NGS) that included at least 80 genes. Clinical data, family history and genetic results were retrospectively analysed. When possible, assessment of first-degree relatives was carried out.

RESULTS

Eighty-seven DCM patients and 308 relatives from 70 families were evaluated. Clinical prevalence of familial disease was 37% (32 patients). Forty-four percent of patients (38 patients) had required heart transplantation. A relevant variant was found in 43 patients (49%), 25 patients (29%) carried variants of unknown significance and in 19 patients (22%) the study was negative. Most genetic variants were found in sarcomeric genes and the yield of genetic testing was higher in patients with familial DCM.

CONCLUSIONS

The yield of genetic testing in our DCM cohort was high, reaching 69% in familial cases. Mutational spectrum was heterogeneous and the identification of the specific aetiology of the disease often provided prognostic information.

LTBP2 knockdown by siRNA reverses myocardial oxidative stress injury, fibrosis and remodelling during dilated cardiomyopathy

AIM

Dilated cardiomyopathy (DCM) is characterised by left ventricular dilation and associated with systolic dysfunction. Recent evidence has reported the high expression of latent transforming growth factor beta binding protein 2 (LTBP2) in heart diseases, which may play a role in regulating multiple biological functions of myocardial cells. Thus, this study set out to investigate the molecular mechanism and effects of LTBP2 in myocardial oxidative stress injury, fibrosis and remodelling in a rat model of DCM, with the involvement of NF-κB signalling pathway.

METHODS

The rat model of DCM was treated with si-LTBP2 and/or activator of NF-κB signalling pathway to examine the haemodynamic indexes, cardiac functions, oxidative stress injury, fibrosis and remodelling. Moreover, in vitro experiments were conducted to verify the regulatory role of LTBP2 and NF-κB signalling pathway in DCM.

RESULTS

LTBP2 was up-regulated in DCM rats. After LTBP2 was knocked down, haemodynamic indexes, HW/BW ratio, collagen volume fraction (CVF) level, positive expression of LTBP2, levels of reactive oxygen species (ROS), malondialdehyde (MDA), interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α), tumour necrosis factor beta 1 (TGF-β1) and brain natriuretic peptide (BNP) were all decreased. Meanwhile, levels of LTBP2, Col-I, Col-III, p65 and p52 were also reduced, while HW, BW and levels of SOD and TAOC were increased. In contrast, activation of NF-κB signalling pathway reversed effects of LTBP2 gene silencing. These findings were confirmed by in vivo experiments.

CONCLUSIONS

LTBP2 silencing can attenuate myocardial oxidative stress injury, myocardial fibrosis and myocardial remodelling in DCM rats by down-regulating the NF-κB signalling pathway.

Applications for Induced Pluripotent Stem Cells in Disease Modelling and Drug Development for Heart Diseases

Induced pluripotent stem cells (iPSCs) are derived from reprogrammed somatic cells by the introduction of defined transcription factors. They are characterised by a capacity for self-renewal and pluripotency. Human (h)iPSCs are expected to be used extensively for disease modelling, drug screening and regenerative medicine. Obtaining cardiac tissue from patients with mutations for genetic studies and functional analyses is a highly invasive procedure. In contrast, disease-specific hiPSCs are derived from the somatic cells of patients with specific genetic mutations responsible for disease phenotypes. These disease-specific hiPSCs are a better tool for studies of the pathophysiology and cellular responses to therapeutic agents. This article focuses on the current understanding, limitations and future direction of disease-specific hiPSC-derived cardiomyocytes for further applications.

Clinical characterisation of a novel SCN5A variant associated with progressive malignant arrhythmia and dilated cardiomyopathy

INTRODUCTION

The SCN5A gene is implicated in many arrhythmogenic and cardiomyopathic processes. We identified a novel SCN5A variant in a family with significant segregation in individuals affected with progressive sinus and atrioventricular nodal disease, atrial arrhythmia, dilated cardiomyopathy, and early sudden cardiac arrest.

METHODS

A patient pedigree was created following the clinical evaluation of three affected individuals, two monozygotic twins and a paternal half-brother, which lead to the evaluation of a paternal half-sister (four siblings with the same father and three mothers) all of whom experienced varying degrees of atrial arrhythmias, conduction disease, and dilated cardiomyopathy in addition to a paternal history of unexplained death in his 50s with similar autopsy findings. The index male underwent sequencing of 58 genes associated with cardiomyopathies. Sanger sequencing was used to provide data for bases with insufficient coverage and for bases in some known regions of genomic segmental duplications. All clinically significant and novel variants were confirmed by independent Sanger sequencing.

RESULTS

All relatives tested were shown to have the same SCN5A variant of unknown significance (p. Asp197His) and the monozygotic twins shared a co-occurring NEXN (p. Glu575*). Segregation analysis demonstrates likely pathogenic trait for the SCN5A variant with an additional possible role for the NEXN variant in combination.

CONCLUSIONS

There is compelling clinical evidence suggesting that the SCN5A variant p. Asp197His may be re-classified as likely pathogenic based on the segregation analysis of our family of interest. Molecular mechanism studies are pending.

Dilated cardiomyopathy: from epidemiologic to genetic phenotypes: A translational review of current literature

Dilated cardiomyopathy (DCM) is characterized by left ventricular dilatation and, consecutively, contractile dysfunction. The causes of DCM are heterogeneous. DCM often results from myocarditis, exposure to alcohol, drugs or other toxins and metabolic or endocrine disturbances. In about 35% of patients, genetic mutations can be identified that usually involve genes responsible for cytoskeletal, sarcomere and nuclear envelope proteins. Due to its heterogeneity, a detailed diagnostic work-up is necessary to identify the specific underlying cause and exclude other conditions with phenotype overlap. Patients with DCM show typical systolic heart failure symptoms, but, with progress of the disease, diastolic dysfunction is present as well. Depending on the underlying pathology, DCM patients also become apparent through arrhythmias, thromboembolic events or cardiogenic shock. Disease progression and prognosis are mostly driven by disease severity and reverse remodelling within the heart. The worst prognosis is seen in patients with lowest ejection fractions or severe diastolic dysfunction, leading to terminal heart failure with subsequent need for left ventricular assist device implantation or heart transplantation. Guideline-based heart failure medication and device therapy reduces the frequency of heart failure hospitalizations and improves survival.

Dilated Cardiomyopathy Due to BLC2-Associated Athanogene 3 (BAG3) Mutations

BACKGROUND

The BAG3 (BLC2-associated athanogene 3) gene codes for an antiapoptotic protein located on the sarcomere Z-disc. Mutations in BAG3 are associated with dilated cardiomyopathy (DCM), but only a small number of cases have been reported to date, and the natural history of BAG3 cardiomyopathy is poorly understood.

OBJECTIVES

This study sought to describe the phenotype and prognosis of BAG3 mutations in a large multicenter DCM cohort.

METHODS

The study cohort comprised 129 individuals with a BAG3 mutation (62% males, 35.1 ± 15.0 years of age) followed at 18 European centers. Localization of BAG3 in cardiac tissue was analyzed in patients with truncating BAG3 mutations using immunohistochemistry.

RESULTS

At first evaluation, 57.4% of patients had DCM. After a median follow-up of 38 months (interquartile range: 7 to 95 months), 68.4% of patients had DCM and 26.1% who were initially phenotype-negative developed DCM. Disease penetrance in individuals >40 years of age was 80% at last evaluation, and there was a trend towards an earlier onset of DCM in men (age 34.6 ± 13.2 years vs. 40.7 ± 12.2 years; p = 0.053). The incidence of adverse cardiac events (death, left ventricular assist device, heart transplantation, and sustained ventricular arrhythmia) was 5.1% per year among individuals with DCM. Male sex, decreased left ventricular ejection fraction. and increased left ventricular end-diastolic diameter were associated with adverse cardiac events. Myocardial tissue from patients with a BAG3 mutation showed myofibril disarray and a relocation of BAG3 protein in the sarcomeric Z-disc.

CONCLUSIONS

DCM caused by mutations in BAG3 is characterized by high penetrance in carriers >40 years of age and a high risk of progressive heart failure. Male sex, decreased left ventricular ejection fraction, and enlarged left ventricular end-diastolic diameter are associated with adverse outcomes in patients with BAG3 mutations.

Importance of Genetic Testing in Dilated Cardiomyopathy: Applications and Challenges in Clinical Practice

Dilated cardiomyopathy (DCM) is a clinical syndrome characterized by left ventricular dilatation and contractile dysfunction. It is the most common cause of heart failure in young adults. The advent of next-generation sequencing has contributed to the discovery of a large amount of genomic data related to DCM. Mutations involving genes that encode cytoskeletal proteins, the sarcomere, and ion channels account for approximately 40% of cases previously classified as idiopathic DCM. In this scenario, geneticists and cardiovascular genetics specialists have begun to work together, building knowledge and establishing more accurate diagnoses. However, proper interpretation of genetic results is essential and multidisciplinary teams dedicated to the management and analysis of the obtained information should be considered. In this review, we approach genetic factors associated with DCM and their prognostic relevance and discuss how the use of genetic testing, when well recommended, can help cardiologists in the decision-making process.

A genome-first approach to aggregating rare genetic variants in LMNA for association with electronic health record phenotypes

PURPOSE

"Genome-first" approaches, in which genetic sequencing is agnostically linked to associated phenotypes, can enhance our understanding of rare variants' contributions to disease. Loss-of-function variants in LMNA cause a range of rare diseases, including cardiomyopathy.

METHODS

We leveraged exome sequencing from 11,451 unselected individuals in the Penn Medicine Biobank to associate rare variants in LMNA with diverse electronic health record (EHR)-derived phenotypes. We used Rare Exome Variant Ensemble Learner (REVEL) to annotate rare missense variants, clustered predicted deleterious and loss-of-function variants into a "gene burden" (N = 72 individuals), and performed a phenome-wide association study (PheWAS). Major findings were replicated in DiscovEHR.

RESULTS

The LMNA gene burden was significantly associated with primary cardiomyopathy (p = 1.78E-11) and cardiac conduction disorders (p = 5.27E-07). Most patients had not been clinically diagnosed with LMNA cardiomyopathy. We also noted an association with chronic kidney disease (p = 1.13E-06). Regression analyses on echocardiography and serum labs revealed that LMNA variant carriers had dilated cardiomyopathy and primary renal disease.

CONCLUSION

Pathogenic LMNA variants are an underdiagnosed cause of cardiomyopathy. We also find that LMNA loss of function may be a primary cause of renal disease. Finally, we show the value of aggregating rare, annotated variants into a gene burden and using PheWAS to identify novel ontologies for pleiotropic human genes.

Hidden in Heart Failure

Current diagnostic strategies fail to illuminate the presence of rare disease in the heart failure population. One-third of heart failure patients are categorised as suffering an idiopathic dilated cardiomyopathy, while others are labelled only as heart failure with preserved ejection fraction. Those affected frequently suffer from delays in diagnosis, which can have a significant impact on quality of life and prognosis. Traditional rhetoric argues that delineation of this patient population is superfluous to treatment, as elucidation of aetiology will not lead to a deviation from standard management protocols. This article emphasises the importance of identifying genetic, inflammatory and infiltrative causes of heart failure to enable patients to access tailored management strategies.