Diagnostic validity and clinical utility of genetic testing for hypertrophic cardiomyopathy: a systematic review and meta-analysis

c.640-814T>C mutation in deep intronic region of alpha-galactosidase A gene is associated with Fabry disease via dominant-negative effect

Fabry disease (FD) is a lysosomal storage disorder resulting from mutations in the alpha-galactosidase A (GLA) gene, characterized by pain, skin lesions, renal failure, and cardiac disease. A 60-year-old proband was hospitalized for recurrent atrial fibrillation (AF) that was unresponsive to medication, with cardiac magnetic resonance imaging (CMRI) revealing left ventricular wall hypertrophy and fat infiltration. Whole-exome sequencing (WES) did not reveal any suspicious pathogenic variants. To further assess the diagnosis, endomyocardial biopsy (EMB) and electron microscopy were performed, revealing abundant zebra bodies in cardiomyocytes, consistent with FD. The diagnosis was ultimately confirmed by GLA enzyme activity analysis (<1.00). Further genetic investigations identified a deep intronic variant (c.640-814T>C) within the GLA gene. Minigene experiments demonstrated that this variant affected the splicing of GLA, resulting in the production of a truncated protein (p.Pro214SerfsTer10). Western blotting (WB) showed that the truncated protein was retained, while immunofluorescence (IF) analysis indicated partial lysosomal localization. In vitro assays confirmed that the retained protein was non-functional and exerted a dominant-negative effect on the normal GLA protein. Molecular docking analysis further revealed that the truncated protein could bind to the wild GLA monomer, significantly reducing cellular GLA enzyme activity. These findings indicate that, beyond being non-functional, the c.640-814T>C mutation may also exerts a dominant-negative effect that impairs the function of the wild GLA protein. These results highlight the importance of recognizing deep intronic mutations in the diagnosis and treatment of FD, contributing to a deeper understanding of the molecular mechanisms, enriching mutation databases, and providing insights into genotype-phenotype correlations.

Clinical Outcome of Hypertrophic Cardiomyopathy in Probands with the Founder Variant c.913_914del in MYBPC3: A Slovenian Cohort Study

Hypertrophic cardiomyopathy is often caused by pathogenic MYBPC3 variants. The study of Italian patients with HCM and MYBPC3(NM_000256.3):c.913_914del showed a higher disease penetrance in males and a higher frequency of arrhythmias compared to patients with other likely pathogenic and pathogenic (LP/P) MYBPC3 variants. We investigated the clinical outcomes of Slovenian probands with MYBPC3 LP/P variants, estimated the variant penetrance and compared the results with an Italian study. We identified 31 haplotype-matched individuals with MYBPC3:c.913_914del and 34 individuals with other LP/P MYBPC3 variants. We observed some significant differences in clinical and echocardiographic characteristics and frequency of adverse cardiac events between Slovenian and Italian probands with MYBPC3:c913_914del. We were unable to replicate previous findings for MYBPC3:c.913_914del, highlighting the complexity of genotype-phenotype associations.

Clinical Features and Prospective Outcomes of Thin-Filament Hypertrophic Cardiomyopathy: Intrinsic Data and Comparative Insights from Other Cohorts

Background/Objectives: Hypertrophic cardiomyopathy (HCM) is the most common genetic heart disease. The most frequently mutated genes encode proteins of the thick filament of the sarcomere, while mutations in thin-filament genes are rare findings in HCM cohorts. Recent studies have revealed distinct mechanisms of disease development linked to thin-filament mutations, highlighting the need for further investigation into this rare subgroup. Methods: A total of 82 adult patients with sarcomere-positive HCM were enrolled. Baseline characteristics and nearly five years of follow-up data from 15 patients with thin-filament mutations were analyzed and compared with those from 67 patients with thick-filament mutations and findings from other studies. Results: Compared to thick-filament HCM patients, individuals with thin-filament mutations exhibited significantly lower maximum left ventricular wall thickness, as measured by both echocardiography (p = 0.024) and cardiac magnetic resonance (p = 0.006), showed more rapid progression to advanced heart failure (HR = 5.6, p = 0.018), and less often underwent septal reduction therapy (p = 0.025). None of the thin-filament HCM patients experienced malignant arrhythmic events. Conclusions: In adults, thin-filament HCM is associated with a 'thinner' phenotype and a more rapid progression to advanced heart failure compared to thick-filament HCM. Data on a higher risk of malignant arrhythmias in thin-filament HCM remain controversial between studies and rather depend on the age of onset and genotype in each particular family.

2024 HRS expert consensus statement on arrhythmias in the athlete: Evaluation, treatment, and return to play

Youth and adult participation in sports continues to increase, and athletes may be diagnosed with potentially arrhythmogenic cardiac conditions. This international multidisciplinary document is intended to guide electrophysiologists, sports cardiologists, and associated health care team members in the diagnosis, treatment, and management of arrhythmic conditions in the athlete with the goal of facilitating return to sport and avoiding the harm caused by restriction. Expert, disease-specific risk assessment in the context of athlete symptoms and diagnoses is emphasized throughout the document. After appropriate risk assessment, management of arrhythmias geared toward return to play when possible is addressed. Other topics include shared decision-making and emergency action planning. The goal of this document is to provide evidence-based recommendations impacting all areas in the care of athletes with arrhythmic conditions. Areas in need of further study are also discussed.

Clinical exome sequencing unravels the diverse spectrum of genetic heterogeneity and genotype-phenotype correlations in hypertrophic cardiomyopathy

BACKGROUND

Catalogues of pathogenic genetic mutations in hypertrophic cardiomyopathy (HCM) are disproportionately small when compared to that of the size of the population with South Asian ancestry and their collective increased risk of heart disease.

METHODS

We conducted clinical exome sequencing of 200 HCM patients to identified cardiomyopathy-associated genetic mutations. The clinical and echocardiographic characteristics of genotype-positive and genotype-negative patients were compared, and the likelihood of detecting a positive genetic test result was evaluated. Allelic burden analysis was done to compare the minor allele frequencies (MAF) of the pathogenic or likely pathogenic (P/LP) variants and variants of uncertain significance (VUSs) identified in the cohort against various population genomics databases.

RESULTS

The genetic yield was 40% for P/LP variants, with MYBPC3 and MYH7 as the predominant sarcomere genes. Younger age-at-diagnosis, family history of HCM, asymmetric hypertrophic (ASH) pattern, the ratio of the interventricular septum to posterior wall thickness (IVS/PW ratio), left atrial (LA) dimensions, severe mitral regurgitation grade (MR grade), late gadolinium enhancement (LGE) detected fibrosis and absence of hypertension were associated with an increased likelihood of HCM-associated variants. Patients who experienced ventricular tachycardia and premature cardiovascular death were significantly likely to carry MYBPC3 or loss-of-function variants. LA and interventricular septal (IVS) dimensions were associated with MYH7 variants. The rare variant burden for P/LP variants and VUSs was significantly enriched in HCM cases compared to population controls.

CONCLUSION

Our study provides a comprehensive evaluation of HCM-associated genetic mutations from an Indian population. The identified genotype-phenotype associations could improve the yield of targeted genetic testing in HCM.

Canadian Cardiovascular Society Clinical Practice Update on Contemporary Management of the Patient With Hypertrophic Cardiomyopathy

Numerous guidelines on the diagnosis and management of hypertrophic cardiomyopathy (HCM) have been published, by learned societies, over the past decade. Although helpful they are often long and less adapted to nonexperts. This writing panel was challenged to produce a document that grew as much from years of practical experience as it did from the peer-reviewed literature. As such, rather than produce yet another set of guidelines, we aim herein to deliver a concentrate of our own experiential learning and distill for the reader the essence of effective and appropriate HCM care. This Clinical Practice Update on HCM is therefore aimed at general cardiologists and other cardiovascular practitioners rather than for HCM specialists. We set the stage with a description of the condition and its clinical presentation, discuss the central importance of "obstruction" and how to look for it, review the role of cardiac magnetic resonance imaging, reflect on the appropriate use of genetic testing, review the treatment options for symptomatic HCM-crucially including cardiac myosin inhibitors, and deal concisely with practical issues surrounding risk assessment for sudden cardiac death, and management of the end-stage HCM patient. Uniquely, we have captured the pediatric experience on our panel to discuss appropriate differences in the management of younger patients with HCM. We ask the reader to remember that this document represents expert consensus opinion rather than dogma and to use their best judgement when dealing with the HCM patient in front of them.

Exploring Health Care Disparities in Genetic Testing and Research for Hereditary Cardiomyopathy: Current State and Future Perspectives

Background  Hereditary cardiomyopathies are commonly occurring myocardial conditions affecting heart structure and function with a genetic or familial association, but the etiology is often unknown. Cardiomyopathies are linked to significant mortality, requiring robust risk stratification with genetic testing and early diagnosis. Hypothesis  We hypothesized that health care disparities exist in genetic testing for hereditary cardiomyopathies within clinical practice and research studies. Methods  In a narrative fashion, we conducted a literature search with online databases such as PubMed/MEDLINE, Google Scholar, EMBASE, and Science Direct on papers related to hereditary cardiomyopathies. A comprehensive analysis of findings from articles in English on disparities in diagnostics and treatment was grouped into four categories. Results  Racial and ethnic disparities in research study enrollment and health care delivery favor White populations and higher socioeconomic status, resulting in differences in the development and implementation of effective genetic screening. Such disparities have shown to be detrimental, as minorities often suffer from disease progression to heart failure and sudden cardiac death. Barriers related to clinical genetic testing included insurance-related issues and health illiteracy. The underrepresentation of minority populations extends to research methodologies, as testing in ethnic minorities resulted in a significantly lower detection rate and diagnostic yield, as well as a higher likelihood of misclassification of variants. Conclusions  Prioritizing minority-based participatory research programs and screening protocols can address systemic disparities. Diversifying research studies can improve risk stratification strategies and impact clinical practice.

Hypertrophic Cardiomyopathy in Underrepresented Populations: Clinical and Genetic Landscape Based on a Russian Single-Center Cohort Study

Hypertrophic cardiomyopathy (HCM) is a common inherited cardiac disorder characterized by marked clinical and genetic heterogeneity. Ethnic groups underrepresented in studies may have distinctive characteristics. We sought to evaluate the clinical and genetic landscape of Russian HCM patients. A total of 193 patients (52% male; 95% Eastern Slavic origin; median age 56 years) were clinically evaluated, including genetic testing, and prospectively followed to document outcomes. As a result, 48% had obstructive HCM, 25% had HCM in family, 21% were asymptomatic, and 68% had comorbidities. During 2.8 years of follow-up, the all-cause mortality rate was 2.86%/year. A total of 5.7% received an implantable cardioverter-defibrillator (ICD), and 21% had septal reduction therapy. A sequencing analysis of 176 probands identified 64 causative variants in 66 patients (38%); recurrent variants were MYBPC3 p.Q1233* (8), MYBPC3 p.R346H (2), MYH7 p.A729P (2), TPM1 p.Q210R (3), and FLNC p.H1834Y (2); 10 were multiple variant carriers (5.7%); 5 had non-sarcomeric HCM, ALPK3, TRIM63, and FLNC. Thin filament variant carriers had a worse prognosis for heart failure (HR = 7.9, p = 0.007). In conclusion, in the Russian HCM population, the low use of ICD and relatively high mortality should be noted by clinicians; some distinct recurrent variants are suspected to have a founder effect; and family studies on some rare variants enriched worldwide knowledge in HCM.

Advanced searching for hypertrophic cardiomyopathy heritability in real practice tomorrow

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease associated with morbidity and mortality at any age. As studies in recent decades have shown, the genetic architecture of HCM is quite complex both in the entire population and in each patient. In the rapidly advancing era of gene therapy, we have to provide a detailed molecular diagnosis to our patients to give them the chance for better and more personalized treatment. In addition to emphasizing the importance of genetic testing in routine practice, this review aims to discuss the possibility to go a step further and create an expanded genetic panel that contains not only variants in core genes but also new candidate genes, including those located in deep intron regions, as well as structural variations. It also highlights the benefits of calculating polygenic risk scores based on a combination of rare and common genetic variants for each patient and of using non-genetic HCM markers, such as microRNAs that can enhance stratification of risk for HCM in unselected populations alongside rare genetic variants and clinical factors. While this review is focusing on HCM, the discussed issues are relevant to other cardiomyopathies.

Severe hypertrophic cardiomyopathy in a patient with a homozygous MYH7 gene variant

Background

Hypertrophic cardiomyopathy is an autosomal dominant disease. The main feature of this disorder is its occurrence in patients who present a left ventricular hypertrophy, unexplained by the loading conditions, usually asymmetric with greatest involvement most commonly of the interventricular septum.Case presentation During a sports medicine control, a ultrasound scan in a 17 years old patient has shown a concentric left ventricular parietal hypertrophy associated with a 23 mm mid- basal interventricular septum thickness. After genetic counselling, a positive family history for hypertrophic cardiac disease and parents' consanguineity was found. The genetic basis of the hypertrophic cardiomyopathy was investigated through a dedicated gene panel. The genetic test has revealed the presence of the variant c.3424G>A (p.Glu1142Lys) in the MYH7 gene in a homozygous state. Genotyping of the parents and of the two brothers revealed the presence of the MYH7 variant in heterozygosity in both parents and in the younger brother. In all of them, variable signs of hypertrophic cardiomyopathy were found.

Conclusions

Our findings report the presence of a homozygous variant in a sarcomeric gene (MYH7) which gave rise to early HCM, whereas the variant in a heterozygous state was associated to much milder cardiac phenotypes in the affected relatives. The onset and the progression of the hypertrophic cardiomyopathy in the reported family is to be referred to the presence of the variant in hetero- or homo-zygosity in a gene dosage manner.

Clinical significance of genetic variation in hypertrophic cardiomyopathy: comparison of computational tools to prioritize missense variants

Hypertrophic cardiomyopathy (HCM) is a common heart disease associated with sudden cardiac death. Early diagnosis is critical to identify patients who may benefit from implantable cardioverter defibrillator therapy. Although genetic testing is an integral part of the clinical evaluation and management of patients with HCM and their families, in many cases the genetic analysis fails to identify a disease-causing mutation. This is in part due to difficulties in classifying newly detected rare genetic variants as well as variants-of-unknown-significance (VUS). Multiple computational algorithms have been developed to predict the potential pathogenicity of genetic variants, but their relative performance in HCM has not been comprehensively assessed. Here, we compared the performance of 39 currently available prediction tools in distinguishing between high-confidence HCM-causing missense variants and benign variants, and we developed an easy-to-use-tool to perform variant prediction benchmarks based on annotated VCF files (VETA). Our results show that tool performance increases after HCM-specific calibration of thresholds. After excluding potential biases due to circularity type I issues, we identified ClinPred, MISTIC, FATHMM, MPC and MetaLR as the five best performer tools in discriminating HCM-associated variants. We propose combining these tools in order to prioritize unknown HCM missense variants that should be closely followed-up in the clinic.