Meta-Analysis of Penetrance and Systematic Review on Transition to Disease in Genetic Hypertrophic Cardiomyopathy

Genetic testing and counseling for hypertrophic cardiomyopathy: An evidence-based practice resource of the National Society of Genetic Counselors

Hypertrophic cardiomyopathy (HCM) is a common hereditary condition affecting approximately 1 in 500 adults. It is characterized by marked clinical heterogeneity with individuals experiencing minimal to no symptoms, while others may have more severe outcomes including heart failure and sudden cardiac death. Genetic testing for HCM is increasingly available due to advances in DNA sequencing technologies and reduced costs. While a diagnosis of HCM is a well-supported indication for genetic testing and genetic counseling, incorporation of genetic services into the clinical setting is often limited outside of expert centers. As genetic counseling and testing have become more accessible and convenient, optimal integration of genomic data into the clinical care of individuals with HCM should be instituted, including delivery via genetic counseling. Drawing on recommendations from recent disease guidelines and systematic evidence reviews, we highlight key recommendations for HCM genetic testing and counseling. This practice resource provides a comprehensive framework to guide healthcare providers in the process of genetic test selection, variant classification, and cascade testing for genetic evaluation of HCM.

Using Genomics to Develop Personalized Cardiovascular Treatments

Advances in genomic technologies have significantly enhanced our understanding of both monogenic and polygenic etiologies of cardiovascular disease. In this review, we explore how the utilization of genomic information is bringing personalized medicine approaches to the forefront of cardiovascular disease management. We describe how genomic data can resolve diagnostic uncertainty, support cascade screening, and inform treatment strategies. We discuss how genome-wide association studies have identified thousands of genetic variants associated with polygenic cardiovascular diseases, and how integrating these insights into polygenic risk scores can enhance personalized risk prediction beyond traditional clinical algorithms. We detail how pharmacogenomics approaches leverage genotype information to guide drug selection and mitigate adverse events. Finally, we present the paradigm-shifting approach of gene therapy, which holds the promise of being a curative intervention for cardiovascular conditions.

Proteomic Analysis of Valsartan for Attenuating Disease Evolution in Early Sarcomeric Hypertrophic Cardiomyopathy (VANISH) Clinical Trial

BACKGROUND

In hypertrophic cardiomyopathy (HCM), the mechanisms through which pathogenic sarcomere variants (G+) lead to left ventricular hypertrophy (LVH) are not understood.

METHODS

VANISH (Valsartan for Attenuating Disease Evolution in Early Sarcomeric Hypertrophic Cardiomyopathy) was a multicenter, double-blind, placebo-controlled randomized trial testing valsartan's ability to attenuate phenotypic progression in early sarcomeric (G+LVH+) and subclinical HCM (G+LVH-). The outcome was a composite Z score reflecting cardiac remodeling from baseline to year 2 (end of study). Baseline and year 2 blood samples were used to quantify 276 proteins using a proximity extension assay (Olink, Sweden). We explored relative differences in protein abundance between early and subclinical HCM at baseline. In addition, we compared proteomic changes between baseline and year 2 in subclinical HCM participants who experienced phenotypic conversion to early HCM (converters) versus nonconverters; early HCM participants receiving valsartan versus placebo; and in association with changes in Z score. Comparisons were made using t test/Mann-Whitney U test, linear mixed models, and generalized linear models, correcting for multiple testing.

RESULTS

Circulating proteins were analyzed in 192 participants (32 subclinical and 160 early HCM [81 allocated to valsartan]). NT-proBNP (N-terminal pro-B-type natriuretic peptide) differentiated early from subclinical HCM and tracked with phenotypic progression in early HCM (1-unit worsening in Z score associated with a 27% increase in NT-proBNP [95% CI, 17-37%]). Some extracellular matrix remodeling proteins showed higher abundance (tissue-type plasminogen activator) in early compared with subclinical HCM or tracked with disease progression (decorin) in early HCM. Growth factors had higher relative abundance in early HCM (fibroblast growth factor-21). While no individual protein was able to distinguish converters from nonconverters, multiprotein the panels lipocalin 2, lectin-like oxidized low-density lipoprotein receptor 1, and either NT-proBNP or interleukin-17 receptor A, could distinguish these groups.

CONCLUSIONS

NT-proBNP was the most robust protein to track progression. Studying pathways involving growth factors and extracellular matrix remodeling may yield additional insights into mechanisms behind disease progression.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT01912534.

The p.Asn271Ile Variant in the TNNT2 Gene Is Associated With Low-Risk Late-Onset Hypertrophic Cardiomyopathy

BACKGROUND

Variants in the cardiac troponin T gene (TNNT2) are a cause of hypertrophic cardiomyopathy (HCM) where mild TNNT2 structural phenotypes may be associated with sudden cardiac death.

OBJECTIVES

This study aims to demonstrate a founder effect in A Coruña (Spain) and characterize the phenotype of the TNNT2 p.Asn271Ile variant in comparison with codon 92 variants, a hotspot previously associated with high risk.

METHODS

Probands and relatives carrying the TNNT2 p.Asn271Ile variant were retrospectively recruited from a multicenter registry. Haplotype analysis was performed in 18 unrelated probands. The primary endpoint was a composite of malignant ventricular arrhythmia and end-stage heart failure. Clinical characteristics, penetrance, and outcomes were compared with codon 92 variants' carriers (p.Arg92Trp/Gln/Pro).

RESULTS

The TNNT2 p.Asn271Ile cohort comprised 159 individuals (46 probands) from families mainly from the A Coruña region (33 of 48). Haplotype analysis revealed a common ancestor around 650 years ago. Late-onset HCM and incomplete age-related penetrance were observed (estimated median diagnosis age 60.1 years). Men were diagnosed 18.4 years before women (P < 0.001). The phenotype was predominantly mild, with a median left ventricular thickness of 17 mm; only 4.2% of patients reached the primary endpoint (3.2% malignant ventricular arrhythmia, 1.1% end-stage heart failure). Codon 92 variants' carriers (76 individuals, 28 probands) had a higher penetrance, being diagnosed 19.4 years earlier, and they exhibited a significantly worse prognosis (primary endpoint in 34.3%; P < 0.001).

CONCLUSIONS

The p.Asn271Ile variant in the TNNT2 gene is associated with late onset HCM, with a low risk of adverse events. Variant-specific rather than gene-specific prognosis should be considered during sudden cardiac death risk assessment.

Altered Lactylation Myocardial Tissue May Contribute to a More Severe Energy-Deprived State of the Tissue and Left Ventricular Outflow Tract Obstruction in HOCM

Hypertrophic cardiomyopathy (HCM) is the most common hereditary cardiovascular disease. In general, obstructive hypertrophic cardiomyopathy (HOCM) is more closely related to severe clinical symptoms and adverse clinical outcomes. Therefore, it is necessary to explore the possible causes of HOCM, which may help physicians better understand the disease and effectively control and manage the progression of the disease. In recent years, the discovery of lactylation has provided scholars with a new direction to explore the occurrence of diseases. In cardiovascular diseases, this post-translational modification can exacerbate cardiac dysfunction, and it can also promote the cardiac repair process after myocardial infarction. In this study, we used the myocardial tissue of mice carrying the Myh7 V878A gene mutation site for protein lactylation detection. Through a further analysis of the enriched pathways using KEGG enrichment, GO enrichment, and Wiki Pathways enrichment, we found that the enriched pathways with lactylation modifications in the HOCM mice mainly included the fatty acid oxidation pathway, the tricarboxylic acid cycle pathway, the adrenergic signaling pathway in cardiomyocytes, and the cardiomyocyte hypertrophy pathway. Among the above pathways, significant changes in lactylation occurred in proteins including Acads, Acaa2, Mdh2, Myl2, and Myl3. We used the COIP experiment to verify the omics results and the ELISA assay to verify the function of the enzymes. We found that a decrease in lactylation modifications also led to a decrease in enzyme function. The abnormalities of these proteins not only lead to abnormalities in energy metabolism in the myocardial tissue of HOCM but also may affect myocardial contractility, resulting in the impaired contractile function of HOCM. The results of this study lay a preliminary theoretical foundation for further exploring the pathogenesis of HOCM.

Considerations for drug trials in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a heterogeneous condition with potentially serious manifestations. Management has traditionally comprised therapies to palliate symptoms and implantable cardioverter-defibrillators to prevent sudden cardiac death. The need for disease-modifying therapies has been recognized for decades. More recently, an increasing number of novel and repurposed therapies hypothesized to target HCM disease pathways have been evaluated, culminating in the recent regulatory approval of mavacamten, a novel oral myosin inhibitor. HCM poses several unique challenges for clinical trials, which are important to recognize when designing trials and interpreting findings. This manuscript discusses the key considerations in the context of recent and ongoing randomized trials, including the roles of genotype, phenotype and symptom status in patient selection, the evidence base for clinical and mechanistic outcome measurements, trial duration and sample size.

Modern clinical genetics in cardiology

Advances in molecular genetics during the past decades led to seminal discoveries in the genetic basis of cardiovascular diseases, resulting in a new understanding of their pathogenesis, determinants of natural history and more recently paved the way for innovative therapies. A significant gap, however, exists between the rapidly increasing knowledge, especially of cardiovascular Mendelian disorders, and the medical applications in daily practice. This paper will focus on the practical issues the cardiologist may be faced with when suspecting a Mendelian disorder. The objective is to review the general issues related to genetic counselling and genetic testing, and to provide key messages for their integration into the medical management of the patients and relatives, according to a precision medicine approach.

Low Penetrance Sarcomere Variants Contribute to Additive Risk in Hypertrophic Cardiomyopathy

BACKGROUND

Classically, hypertrophic cardiomyopathy (HCM) has been viewed as a single-gene (monogenic) disease caused by pathogenic variants in sarcomere genes. Pathogenic sarcomere variants are individually rare and convey high risk for developing HCM (highly penetrant). Recently, important polygenic contributions have also been characterized. Low penetrance sarcomere variants (LowSVs) at intermediate frequencies and effect sizes have not been systematically investigated. We hypothesize that LowSVs may be common in HCM with substantial influence on disease risk and severity.

METHODS

Among all sarcomere variants observed in the Sarcomeric Human Cardiomyopathy Registry (SHaRe), we identified putative LowSVs defined by (1) population frequency greater than expected for highly penetrant (monogenic) HCM (allele frequency >5×10-5 in the Genome Aggregation Database, gnomAD) and (2) moderate enrichment (>2×) in patients with HCM compared with gnomAD. LowSVs were examined for their association with disease severity and clinical outcomes. Functional effects of selected LowSVs were assessed using induced pluripotent stem cell-derived cardiomyocytes. Association of LowSVs with HCM-adjacent traits in the general population was tested using UK Biobank cardiac magnetic resonance imaging data.

RESULTS

Among 6045 patients and 1159 unique variants in sarcomere genes, 12 LowSVs were identified. LowSVs were collectively common in the general population (1:350) and moderately enriched in HCM (aggregate odds ratio, 14.9 [95% CI, 12.5-17.9]). Isolated LowSVs were associated with an older age of HCM diagnosis and fewer adverse events. However, LowSVs in combination with a pathogenic sarcomere variant conferred higher morbidity (eg, composite adverse event hazard ratio, 5.4 [95% CI, 3.0-9.8] versus single pathogenic sarcomere variant, 2.0 [95% CI, 1.8-2.2]; P<0.001). An intermediate functional impact was validated for 2 specific LowSVs-MYBPC3 c.442G>A (partial splice gain) and TNNT2 c.832C>T (intermediate effect on contractile mechanics). Cardiac magnetic resonance imaging analysis of the general population revealed 5 of 12 LowSVs were significantly associated with HCM-adjacent traits without overt HCM.

CONCLUSIONS

This study establishes a new class of low penetrance sarcomere variants that are relatively common in the population. When penetrant, isolated LowSVs cause mild HCM. In combination with pathogenic sarcomere variants, LowSVs markedly increase disease severity, supporting a clinically significant additive effect. Last, LowSVs also contribute to age-related remodeling even in the absence of overt HCM.

Case report: Severe arrhythmogenic cardiomyopathy in a young girl with compound heterozygous DSG2 and MYBPC3 variants with a 6-year follow-up

Introduction

Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disorder characterized by progressive fibrofatty replacement of the myocardium. In the Japanese population, variants of the desmoglein-2 (DSG2) gene are a major cause of ACM, typically following an autosomal recessive inheritance pattern. Myosin-binding protein C (MYBPC3) variants are primarily associated with hypertrophic cardiomyopathy (HCM). Here, we report a severe pediatric case of ACM associated with compound heterozygous DSG2 and MYBPC3 variants.

Case Presentation

A 6-year-old asymptomatic girl was diagnosed with ACM based on abnormal electrocardiogram findings, including epsilon waves, and T-wave inversions in leads V1-6 and III. Echocardiography revealed right ventricular (RV) dilatation (RV outflow tract diameter/body surface area: 22.9 mm/m2) and reduced RV function (fractional area change: 18.0%). Cardiac magnetic resonance imaging confirmed RV dysfunction (ejection fraction [EF]: 9.7%) and left ventricular (LV) involvement (EF: 48.9%). Genetic testing identified compound heterozygous DSG2 variants (p.Arg119* and p. Arg292Cys) and an MYBPC3 variant (p.Arg820Gln). The patient remained asymptomatic until age 10.5 years, when she developed heart failure requiring hospitalization. Imaging revealed severe biventricular dilatation (LV end-diastolic volume index: 149.5 mL/m2; RV end-diastolic volume index: 255.9 mL/m2) and biventricular dysfunction (LVEF: 9.5%; RVEF: 9.7%). Despite medical management, the patient's condition progressively worsened, and she was deemed eligible for heart transplantation.

Discussion

This case illustrates the potential for severe pediatric ACM associated with compound heterozygous DSG2 variants and a MYBPC3 variant. The DSG2 variants likely played a primary role disease pathogenesis, while the MYBPC3 variant may have exacerbated the phenotype. The coexistence of desmosomal and sarcomeric gene variants is rare in cardiomyopathies, making genotype-phenotype correlations complex. Further research is needed to elucidate the interplay between these genetic factors.

Conclusion

This case underscores the genetic heterogeneity and phenotypic variability in inherited cardiomyopathies. It emphasizes the importance of comprehensive genetic testing and close monitoring of affected individuals and their families.

Family screening for hypertrophic cardiomyopathy: Initial cardiologic assessment, and long-term follow-up of genotype-positive phenotype-negative individuals

AIMS

(i) Investigate the prevalence of hypertrophic cardiomyopathy (HCM) in individuals with pathogenic/likely pathogenic (P/LP) gene variants detected through family cascade testing in relatives, and (ii) evaluate phenotypic progression in genotype-positive phenotype-negative (G+/P-) individuals during follow-up.

RESULTS

From 2000 to 2023, 273 individuals underwent cardiologic evaluation following P/LP variant detection through family screening. Upon initial evaluation, HCM was diagnosed in 128 (47 %) individuals. Comparing with 145 G+/P- individuals, HCM patients were older (48 vs 38 years, p < 0.001) and more likely male (57 % vs 34 %, p < 0.001). During follow-up (median 11 years), 14 (11 %) of the HCM patients died (two from sudden cardiac death), four (3 %) underwent myectomy, 15 (12 %) developed atrial fibrillation and 17 (13 %) required implantable cardioverter-defibrillator implantation (15 primary prevention, 88 %). HCM-related adverse outcomes correlated with younger diagnosis age. During follow-up (median 8 years) of 118 (out of 145) G+/P- subjects with at least one year of follow-up, seven (6 %) individuals (71 % female, diagnosed age 39-77, after median follow-up 6 years) developed HCM (mean maximal wall thickness increasing from 10.2 mm to 13.3 mm). In this G+/P- cohort, significant echocardiographic changes from baseline to last visit were negligible. Over half (56 %) had <1 mm change of maximal wall thickness. No adverse cardiac outcomes occurred.

CONCLUSION

The initial evaluation was high-yield, with HCM being diagnosed in 47 % of G+ individuals, more frequently in older males. Over a median 8-year follow-up, 6 % of G+/P- individuals developed mild HCM, with no adverse cardiac outcomes. These data support initial screening in all first degree relatives, but (very) low-frequency cardiologic evaluations for G+/P- individuals thereafter.

Inherited Hypertrabeculation? Genetic and Clinical Insights in Blood Relatives of Genetically Affected Left Ventricular Excessive Trabeculation Patients

Genetically determined left ventricular excessive trabeculation (LVET) has a wide clinical spectrum ranging from asymptomatic subjects to severe heart failure with arrhythmias and thromboembolic events. Unlike other cardiomyopathies, the relatives of LVET patients never reach the spotlight of guidelines and clinical practice, although these family members can be often affected by these conditions. Thus, we aimed to investigate the relatives of LVET by multidimensional analysis, such as genetic testing, ECG and cardiac ultrasound (ECHO). We included 55 blood relatives from the family of 18 LVET patients (male = 27, age = 44 ± 20.8y), who underwent anamnesis registration. With Sanger sequencing, the relatives were classified into genetically positive (GEN-pos) and unaffected (GEN-neg) subgroups. In addition to regular ECG parameters, Sokolow-Lyon Index (SLI) values were calculated. 2D ECHO images were analysed with TomTec Arena, evaluating LV volumetric, functional (EF) and strain parameters. Individuals were categorized into JENNI-pos and JENNI-neg morphological subgroups according to the Jenni LVET ECHO criteria. Family history showed frequent involvement (arrhythmia 61%, stroke 56%, syncope 39%, sudden cardiac death 28%, implanted device 28%), as well as personal anamnesis (subjective symptoms 75%, arrhythmias 44%). ECG and ECHO parameters were within the normal range. In terms of genetics, 78% of families and 38% of relatives carried the index mutation. LV_SLI and QT duration were lower in the GEN-pos group; ECHO parameters were comparable in the subgroups. Morphologically, 33% of the relatives met Jenni-LVET criteria were genetically affected and showed lower LV_EF values. The frequently found genetic, morphological and clinical involvement may indicate the importance of screening and, if necessary, regular follow-up of relatives in the genetically affected LVET population.

Transcriptomic and genetic profiling in a spontaneous non-human primate model of hypertrophic cardiomyopathy and sudden cardiac death

Hypertrophic cardiomyopathy (HCM) afflicts humans, cats, pigs, and rhesus macaques. Disease sequelae include congestive heart failure, thromboembolism, and sudden cardiac death (SCD). Sarcomeric mutations explain some human and cat cases, however, the molecular basis in rhesus macaques remains unknown. RNA-Seq of the LV tissues of five HCM-affected and seven healthy control rhesus macaques was employed for differential transcriptomic analyses. DNA from 15 severely HCM-affected and 21 healthy geriatric rhesus macaques were selected for whole-genome sequencing. A genome-wide association study (GWAS) of disease status and SCD outcome was performed. 614 down- and 1,065 upregulated differentially expressed genes (DEGs) were identified between groups. The top DEG (MAFF) was overexpressed in affected animals (log2FoldChange = 4.71; PAdjusted-value = 1.14E-133). Channelopathy-associated enriched terms were identified in ~ 57% of downregulated DEGs providing transcriptomic evidence of hypertrophic and arrhythmic disease processes. For GWAS, no putative variant withstood segregation. Polygenic modeling analysis resulted in poor prediction power and burden testing could not explain HCM by an association of multiple variants in any gene. Neither single nor compound genetic variant(s), or identified polygenic profile, suggest complex genotype-phenotype interactions in rhesus macaques. Brought forth is an established dataset of robustly phenotyped rhesus macaques as an open-access resource for future cardiovascular disease genetic studies.

Multimodal ultrasound assessment of myocardial perfusion and contractile function in patients with hypertrophic cardiomyopathy and their first-degree relatives

OBJECTIVES

Hypertrophic cardiomyopathy (HCM) frequently leads to myocardial ischemia and cardiac dysfunction. Even genotype-positive/phenotype-negative (G+/P-) individuals, carriers of pathogenic sarcomere gene mutations without left ventricular hypertrophy, remain at risk of progression to clinical HCM. This study aims to evaluate myocardial perfusion and contractile function in familial HCM patients and their first-degree relatives using myocardial contrast echocardiography (MCE) and velocity vector imaging (VVI), in order to identify early myocardial dysfunction and at-risk individuals within families.

METHODS

Thirty-five genetically confirmed HCM patients with left ventricular hypertrophy were assigned to a G+/P+ group. A total of 30 first-degree relatives carrying sarcomere mutations but without echocardiographic evidence of left ventricular hypertrophy were assigned to a G+/P- group. A total of 38 age- and sex-matched gene-negative healthy family members served as controls. All participants underwent MCE and VVI assessments. Myocardial perfusion parameters, including peak intensity (PI), time to peak concentration (TP), and the ratio of declining intensity and declining time (dI/dT), as well as strain parameters including global longitudinal strain (GLS), global radial strain (GRS), and global circumferential strain (GCS) were recorded and analyzed for differences and correlations.

RESULTS

Compared to both the G+/P- and normal control groups, the G+/P+ group had significantly lower PI, dI/dT, GLS, and GRS, along with significantly increased TP (all P<0.05). GLS and GRS were positively correlated with PI (r=0.629 and r=0.613, respectively; both P<0.01) and negatively correlated with TP (r=-0.597 and r=-0.571, respectively; both P<0.01). Compared to the normal control group, the G+/P- group showed a significant reduction in GLS (P<0.05), but no significant differences in GRS, GCS, PI, TP, or dI/dT (all P>0.05).

CONCLUSIONS

Myocardial contractile dysfunction in HCM patients is closely related to impaired perfusion. Even in the absence of wall hypertrophy, sarcomere mutation carriers show early signs of subclinical left ventricular dysfunction. MCE and VVI can quantitatively assess myocardial perfusion and function, offering valuable tools for early detection and risk stratification in HCM patients and their relatives.

Three Novel Pathogenic Variants in Unrelated Vietnamese Patients with Cardiomyopathy

Background: Cardiomyopathy, including dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM), is a major cause of heart failure (HF) and a leading indication for heart transplantation. Of these patients, 20-50% have a genetic cause, so understanding the genetic basis of cardiomyopathy will provide knowledge about the pathogenesis of the disease for diagnosis, treatment, prevention, and genetic counseling for families. Methods: This study collected nine patients from different Vietnamese families for genetic analysis at The Cardiovascular Center, E Hospital, Hanoi, Vietnam. The patients were diagnosed with cardiomyopathy based on clinical symptoms. Whole-exome sequencing (WES) was performed in the Vietnamese patients to identify variants associated with cardiomyopathy, and the Sanger sequencing method was used to validate the variants in the patients' families. The influence of the variants was predicted using in silico analysis tools. Results: Nine heterozygous variants were detected as a cause of disease in the patients, three of which were novel variants, including c.284C>G, p.Pro95Arg in the MYL2 gene, c.2356A>G, p.Thr786Ala in the MYH7 gene, and c.1223T>A, p.Leu408Gln in the DES gene. Two other variants were pathogenic variants (c.602T>C, p.Ile201Thr in the MYH7 gene and c.1391G>C, p.Gly464Ala in the PTPN11 gene), and four were variants of uncertain significance in the ACTA2, ANK2, MYOZ2, and PRKAG2 genes. The results of the in silico prediction software showed that the identified variants were pathogenic and responsible for the patients' DCM. Conclusions: Our results contribute to the understanding of cardiomyopathy pathogenesis and provide a basis for diagnosis, treatment, prevention, and genetic counseling.

The Genetic Factors Influencing Cardiomyopathies and Heart Failure across the Allele Frequency Spectrum

Heart failure (HF) remains a major cause of mortality and morbidity worldwide. Understanding the genetic basis of HF allows for the development of disease-modifying therapies, more appropriate risk stratification, and personalised management of patients. The advent of next-generation sequencing has enabled genome-wide association studies; moving beyond rare variants identified in a Mendelian fashion and detecting common DNA variants associated with disease. We summarise the latest GWAS and rare variant data on mixed and refined HF aetiologies, and cardiomyopathies. We describe the recent understanding of the functional impact of titin variants and highlight FHOD3 as a novel cardiomyopathy-associated gene. We describe future directions of research in this field and how genetic data can be leveraged to improve the care of patients with HF.

Genetics of hypertrophic cardiomyopathy: established and emerging implications for clinical practice

Pathogenic variation in genes encoding proteins of the cardiac sarcomere is responsible for 30%-40% of cases of hypertrophic cardiomyopathy. The main clinical utility of genetic testing is to provide diagnostic confirmation and facilitation of family screening. It also assists in the detection of aetiologies, which require distinct monitoring and treatment approaches. Other clinical applications, including the use of genetic information to inform risk prediction models, have been limited by the challenge of establishing robust genotype-phenotype correlations with actionable consequences, but new data on the interaction between rare and common genetic variation, as well as the emergence of therapies targeting disease-specific pathogenic mechanisms, herald a new era for genetic testing in routine practice.

Phenotypic Spectrum of Subclinical Sarcomere-Related Hypertrophic Cardiomyopathy and Transition to Overt Disease

Genetic hypertrophic cardiomyopathy (HCM) is classically caused by pathogenic/likely pathogenic variants in sarcomere genes (G+). Currently, HCM is diagnosed if there is unexplained left ventricular (LV) hypertrophy with LV wall thickness ≥15 mm in probands or ≥13 mm in at-risk relatives. Although LV hypertrophy is a key feature, this binary metric does not encompass the full constellation of phenotypic features, particularly in the subclinical stage of the disease. Subtle phenotypic manifestations can be identified in sarcomere variant carriers with normal LV wall thickness, before diagnosis with HCM (G+/LV hypertrophy-; subclinical HCM). We conducted a systematic review to summarize current knowledge about the phenotypic spectrum of subclinical HCM and factors influencing penetrance and expressivity. Although the mechanisms driving the development of LV hypertrophy are yet to be elucidated, activation of profibrotic pathways, impaired relaxation, abnormal Ca2+ signaling, altered myocardial energetics, and microvascular dysfunction have all been identified in subclinical HCM. Progression from subclinical to clinically overt HCM may be more likely if early phenotypic manifestations are present, including ECG abnormalities, longer mitral valve leaflets, lower global E' velocities on Doppler echocardiography, and higher serum N-terminal propeptide of B-type natriuretic peptide. Longitudinal studies of variant carriers are critically needed to improve our understanding of penetrance, characterize the transition to disease, identify risk predictors of phenotypic evolution, and guide the development of novel treatment strategies aimed at influencing disease trajectory.

Hypertrophic Cardiomyopathy

PURPOSE OF REVIEW

Hypertrophic cardiomyopathy (HCM) is a common inherited cardiac condition with potential for severe complications including sudden cardiac death. Early diagnosis allows appropriate risk stratification and prompt intervention to minimise the potential for adverse outcomes. The implications of poorly coordinated screening are significant, either missing relatives at high-risk or burdening low-risk individuals with a diagnosis associated with reduced life expectancy. We aim to guide clinicians through the diagnostic pathway through to novel treatment options. Several conditions mimic the condition, and we discuss the phenocopies and how to differentiate from HCM.

RECENT FINDINGS

We summarise the latest developments informing clinical decision making in the modern era of myosin inhibitors and future gene editing therapies. Early identification will enable prompt referral to specialist centres. A diagnostic flowchart is included, to guide the general cardiology and heart failure clinician in important decision making regarding the care of the HCM patient and importantly their relatives at risk. We have highlighted the importance of screening because genotype-positive/phenotype-negative patients are likely to have the most to gain from novel therapies.

High prevalence of ALPK3 premature terminating variants in Korean hypertrophic cardiomyopathy patients

Background

The alpha-protein kinase 3 (ALPK3) gene (OMIM: 617608) is associated with autosomal recessive familial hypertrophic cardiomyopathy-27 (CMH27, OMIM: 618052). Recently, several studies have shown that monoallelic premature terminating variants (PTVs) in ALPK3 are associated with adult-onset autosomal dominant hypertrophic cardiomyopathy (HCMP). However, these studies were performed on patient cohorts mainly from European Caucasian backgrounds.

Methods

To determine if this finding is replicated in the Korean HCMP cohort, we evaluated 2,366 Korean patients with non-syndromic HCMP using exome sequencing and compared the cohort dataset with three independent population databases.

Results

We observed that monoallelic PTVs in ALPK3 were also significantly enriched in Korean patients with HCMP with an odds ratio score of 10-21.

Conclusions

We suggest that ALPK3 PTV carriers be considered a risk group for developing HCMP and be monitored for cardiomyopathies.