Familial hypertrophic cardiomyopathy: clinical features, molecular genetics and molecular genetic testing

Prognosis of patients with familial hypertrophic cardiomyopathy: A single-center cohort study with ten-year follow-up by propensity score matching analysis

Objectives

Hypertrophic cardiomyopathy (HCM) is the most common hereditary cardiomyopathy. However, few studies have investigated the prognosis of familial HCM (FHCM) through clinical data. The purpose of this study was to compare the clinical outcomes of FHCM and non-FHCM through propensity score matching analysis.

Methods and results

The cohort study included 1243 patients with HCM between 1996 and 2013 in Fuwai Hospital, Chinese Academy of Medical Sciences, among whom 125 patients had FHCM. During a mean follow-up of 7.6 ± 3.8 years (interquartile range: (IQR) 5.0-10.0 years), 217 (16.57%) of the 1243 patients had died, including 3 patients who underwent cardiac transplantation. Using 30 demographic and clinical variables, a 4:1 propensity score matched cohort for FHCM was established. The stepwise variable selection procedure for the Cox proportional hazards model was performed to identify the factors associated with mortality and competing risk regression analysis was performed to analyze the competitive risk of cardiovascular and non-cardiovascular mortality. The results showed that FHCM patients had a higher risk of cardiovascular mortality/cardiac transplantation (log-rank χ² = 6.8, P = 0.0084) and an increased tendency of sudden cardiac death (SCD) (log-rank χ² = 3.2, P = 0.074) compared with non-FHCM patients, but there was no difference in all-cause mortality (log-rank χ² = 2.7, P = 0.1) between the two groups. Moreover, the Cox model showed that FHCM was an independent prognostic predictor for cardiovascular mortality/cardiac transplantation in HCM patients.

Conclusion

FHCM patients had a higher risk of cardiovascular mortality/cardiac transplantation and a higher tendency of SCD than non-FHCM patients, but there was no difference in all-cause mortality. Moreover, FHCM was an independent prognostic predictor for cardiovascular mortality/cardiac transplantation in HCM patients.

Pharmacotherapy for the treatment of obstructive hypertrophic cardiomyopathy

Introduction: Hypertrophic cardiomyopathy (HCM) is one of the most common genetic heart diseases and represents a leading cause of sudden cardiac death as well as a prevalent cause of heart failure and stroke. HCM is characterized by a very complex pathophysiology, consisting of heterogeneous clinical manifestations and natural history. Left ventricular outflow tract (LVOT) obstruction has been considered the most knowable feature of HCM since the initial clinical descriptions of the disease.Areas covered: In this review, the authors discuss the most recent reports on the pharmacological treatment of obstructive HCM, mainly based on three different levels of intervention: control of symptoms, cardiac metabolism modulation and disease-modifying approaches, including genetic preventive therapies.Expert opinion: There are presently limited data supporting pharmacological interventions for this complex disease. However, an improved understanding of HCM pathophysiology will allow the development of novel treatment options. Two important key messages are to further study drugs with negative but limited previous results and to design new and larger trials for those molecules that have already produced positive results in HCM, especially for pressure gradients and symptoms control.

Next generation sequencing applications for cardiovascular disease

The Human Genome Project (HGP), as the primary sequencing of the human genome, lasted more than one decade to be completed using the traditional Sanger's method. At present, next-generation sequencing (NGS) technology could provide the genome sequence data in hours. NGS has also decreased the expense of sequencing; therefore, nowadays it is possible to carry out both whole-genome (WGS) and whole-exome sequencing (WES) for the variations detection in patients with rare genetic diseases as well as complex disorders such as common cardiovascular diseases (CVDs). Finding new variants may contribute to establishing a risk profile for the pathology process of diseases. Here, recent applications of NGS in cardiovascular medicine are discussed; both Mendelian disorders of the cardiovascular system and complex genetic CVDs including inherited cardiomyopathy, channelopathies, stroke, coronary artery disease (CAD) and are considered. We also state some future use of NGS in clinical practice for increasing our information about the CVDs genetics and the limitations of this new technology. Key messages Traditional Sanger's method was the mainstay for Human Genome Project (HGP); Sanger sequencing has high fidelity but is slow and costly as compared to next generation methods. Within cardiovascular medicine, NGS has been shown to be successful in identifying novel causative mutations and in the diagnosis of Mendelian diseases which are caused by a single variant in a single gene. NGS has provided the opportunity to perform parallel analysis of a great number of genes in an unbiased approach (i.e. without knowing the underlying biological mechanism) which probably contribute to advance our knowledge regarding the pathology of complex diseases such as CVD.

Next generation sequencing in cardiomyopathy: towards personalized genomics and medicine

Next generation sequencing (NGS) is perhaps one of the most exciting advances in the field of life sciences and biomedical research in the last decade. With the availability of massive parallel sequencing, human DNA blueprint can be decoded to explore the hidden information with reduced time and cost. This technology has been used to understand the genetic aspects of various diseases including cardiomyopathies. Mutations for different cardiomyopathies have been identified and cataloging mutations on phenotypic basis are underway and are expected to lead to new discoveries that may translate to novel diagnostic, prognostic and therapeutic targets. With ease in handling NGS, cost effectiveness and fast data output, NGS is now considered as a diagnostic tool for cardiomyopathy by providing targeted gene sequencing. In addition to the number of genetic variants that are identified in cardiomyopathies, there is a need of quicker and easy way to screen multiple genes associated with the disease. In this review, an attempt has been made to explain the NGS technology, methods and applications in cardiomyopathies and their perspective in clinical practice and challenges which are to be addressed.

Next-generation sequencing technology in the genetics of cardiovascular disease

In recent years, next-generation sequencing (NGS) technologies have revolutionized approaches to genetic studies, making whole-genome sequencing a possible way for obtaining global genomic information. At present, three most NGS platforms are used in genetics for clonally amplified templates. These technologies share general processing steps but differing in specific technical details that determine their limits or advantages. NGS has been recently shown to have great potential for identifying novel causative mutations in different disorders. It is expected that the NGS will be increasingly important in the study of inherited and complex traits such as cardiovascular diseases (CVDs). Indeed, the identification and characterization of genes that enhance prediction of CVDs risk remain an important challenge for improving prevention and treatment.

Pharmacological treatment options for hypertrophic cardiomyopathy: high time for evidence

Hypertrophic cardiomyopathy (HCM) is the most common genetic heart disease, affecting over one million individuals in Europe. Hypertrophic cardiomyopathy patients often require pharmacological intervention for control of symptoms, dynamic left ventricular outflow obstruction, supraventricular and ventricular arrhythmias, and microvascular ischaemia. Current treatment strategies in HCM are predicated on the empirical use of long-standing drugs, such as beta-adrenergic and calcium blockers, although with little evidence supporting their clinical benefit in this disease. In the six decades since the original description of the disease, <50 pharmacological studies enrolling little over 2000 HCM patients have been performed, the majority of which were small, non-randomized cohorts. As our understanding of the genetic basis and pathophysiology of HCM improves, the availability of transgenic and preclinical models uncovers clues to novel and promising treatment modalities. Furthermore, the number of patients identified and followed at international referral centres has grown steadily over the decades. As a result, the opportunity now exists to implement adequately designed pharmacological trials in HCM, using established as well as novel drug therapies, to potentially intervene on the complex pathophysiology of the disease and alter its natural course. Therefore, it is timely to review the available evidence for pharmacological therapy of HCM patients, highlight the most relevant gaps in knowledge, and address some of the most promising areas for future pharmacological research, in an effort to move HCM into the era of evidence-based management.

Next generation sequencing for clinical diagnostics-principles and application to targeted resequencing for hypertrophic cardiomyopathy: a paper from the 2009 William Beaumont Hospital Symposium on Molecular Pathology

During the past five years, new high-throughput DNA sequencing technologies have emerged; these technologies are collectively referred to as next generation sequencing (NGS). By virtue of sequencing clonally amplified DNA templates or single DNA molecules in a massively parallel fashion in a flow cell, NGS provides both qualitative and quantitative sequence data. This combination of information has made NGS the technology of choice for complex genetic analyses that were previously either technically infeasible or cost prohibitive. As a result, NGS has had a fundamental and broad impact on many facets of biomedical research. In contrast, the dissemination of NGS into the clinical diagnostic realm is in its early stages. Though NGS is powerful and can be envisioned to have multiple applications in clinical diagnostics, the technology is currently complex. Successful adoption of NGS into the clinical laboratory will require expertise in both molecular biology techniques and bioinformatics. The current report presents principles that underlie NGS including sequencing library preparation, sequencing chemistries, and an introduction to NGS data analysis. These concepts are subsequently further illustrated by showing representative results from a case study using NGS for targeted resequencing of genes implicated in hypertrophic cardiomyopathy.

Basic Mechanisms Mediating Cardiomyopathy and Heart Failure in Aging

Biological aging represents the major risk factor for the development of heart failure (HF), malignancies, and neurodegenerative diseases. While risk factors such as lifestyle patterns, genetic traits, blood lipid levels, and diabetes can contribute to its development, advancing age remains the most determinant predictor of cardiac disease. Several parameters of left ventricular function may be affected with aging, including increased duration of systole, decreased sympathetic stimulation, and increased left ventricle ejection time, while compliance decreases. In addition, changes in cardiac phenotype with diastolic dysfunction, reduced contractility, left ventricular hypertrophy, and HF, all increase in incidence with age. Given the limited capacity that the heart has for regeneration, reversing or slowing the progression of these abnormalities poses a major challenge. In this chapter, we present a discussion on the molecular and cellular mechanisms involved in the pathogenesis of cardiomyopathies and HF in aging and the potential involvement of specific genes identified as primary mediators of these diseases.

The cardiac troponin C mutation Leu29Gln found in a patient with hypertrophic cardiomyopathy does not alter contractile parameters in skinned murine myocardium

The present study investigates the effects of the first mutation of troponin C (hcTnC^L29Q) found in a patient with hypertrophic cardiomyopathy (HCM) on force–pCa relations and the interplay with phosphorylation of sarcomeric PKA substrates. In triton-skinned murine cardiac fibers, the endogenous mcTnC was extracted and the fibers were subsequently reconstituted with recombinant wild-type and mutant hcTnC. Force–pCa relations of preparations containing hcTnC^L29Q or hcTnC^WT were similar. Incubation of fibers reconstituted with the recombinant proteins with phosphatase to dephosphorylate sarcomeric PKA substrates induced an increase in Ca²⁺ sensitivity, slightly more pronounced (0.04 pCa units) in hcTnC^L29Q-containing fibers. Incubation of the dephosphorylated fibers with PKA induced significant rightward shifts of force–pCa relations of similar magnitude with both, hcTnC^L29Q and hcTnC^WT. No significant effects of hcTnC^L29Q on the velocity of unloaded shortening were observed. In conclusion, no major differences in contractile parameters of preparations containing hcTnC^L29Q compared to hcTnC^WT were observed. Therefore, it appears unlikely that hcTnC^L29Q induces the development of HCM by affecting the regulation of Ca²⁺-activated force and interference with PKA-mediated modulation of the Ca²⁺ sensitivity of contraction.

Clinical utility of genetic tests for inherited hypertrophic and dilated cardiomyopathies

Genetic testing has become an increasingly important part of medical practice for heritable form of cardiomyopathies. Hypertrophic cardiomyopathy and about 50% of idiopathic dilatative cardiomyopathy are familial diseases, with an autosomal dominant pattern of inheritance.

Some genotype-phenotype correlations can provide important information to target DNA analyses in specific genes. Genetic testing may clarify diagnosis and help the optimal treatment strategies for more malignant phenotypes. In addition, genetic screening of first-degree relatives can help early identification and diagnosis of individuals at greatest risk for developing cardiomyopathy, allowing to focus clinical resources on high-risk family members.

This paper provides a concise overview of the genetic etiology as well as the clinical utilities and limitations of genetic testing for the heritable cardiomyopathies.

Ile90Met, a novel mutation in the cardiac troponin T gene for familial hypertrophic cardiomyopathy in a Chinese pedigree

To identify the disease-causing gene for a large multi-generational Chinese family affected by familial hypertrophic cardiomyopathy (FHCM), genome-wide screening was carried out in a Chinese family with FHCM using micro-satellite markers, and linkage analysis was performed using the MLINK program. The disease locus was mapped to 1q32 in this family. Screening for a mutation in the cardiac troponin T (cTnT) gene was performed by a PCR and sequencing was done with an ABI Prism 3700 sequencer. A novel C-->G transition located in the ninth exon of the cTnT gene, leading to a predicted amino acid residue change from Ile to Met at codon 90, was identified in all individuals with hypertrophic cardiomyopathy (HCM). The results presented here strongly suggest that Ile90Met, a novel mutation in the cTnT gene, is causative agent of HCM in this family.

Myofilament protein gene mutation screening and outcome of patients with hypertrophic cardiomyopathy

OBJECTIVE

To determine the influence of a positive genetic test for hypertrophic cardiomyopathy (HCM) on clinical outcome.

PATIENTS AND METHODS

A cohort of 203 unrelated patients with HCM (mean +/- SD age, 50+/-18 years) was enrolled from January 1, 2002, through December 31, 2003. They were followed up for a mean +/- SD time of 4.0+/-1.7 years after genetic testing of the 8 HCM-susceptibility genes that encode key sarcomeric/myofilament proteins. The clinical phenotype of those with a positive genetic test (myofilament-positive HCM) was compared with those with a negative genetic test (myofilament-negative HCM).

RESULTS

In this cohort of 203 patients, 87 mutations were identified in 126 patients (myofilament-positive HCM, 62%); the remaining 77 patients (38%) were myofilament-negative. Despite similar baseline features, patients with myofilament-positive HCM showed increased risk of the combined end points of cardiovascular death, nonfatal stroke, or progression to New York Heart Association class III or IV compared with the patients with myofilament-negative HCM (25% vs 7%, respectively; independent hazard ratio, 4.27; P=.008). These end points occurred at any age among patients with myofilament-positive HCM (range, 14-86 years), but only in those aged 65 years and older among patients with myofilament-negative HCM. Moreover, patients with myofilament-positive HCM showed greater probability of severe left ventricular systolic and diastolic dysfunction, defined as an ejection fraction of less than 50% and a restrictive filling pattern (P=.02 and P<.02, respectively, vs myofilament-negative HCM).

CONCLUSION

Screening for sarcomere protein gene mutations in HCM identifies a broad subgroup of patients with increased propensity toward long-term impairment of left ventricular function and adverse outcome, irrespective of the myofilament (thick, intermediate, or thin) involved.

A PCR-based integrated protocol for the structural analysis of the 13th exon of the human beta-myosin heavy chain gene (MYH7): development of a diagnostic tool for HCM disease

Familial Hypertrophic Cardiomyopathy (FHC) constitutes a genetic disease of the sarcomere characterized by a Mendelian pattern of inheritance. A variety of different mutations affecting the at least eight sarcomeric gene products has been identified and the majority of them appear to function through a dominant negative mechanism. Family history analysis and genetic counseling have been widely adopted as integral tools for the evaluation and management of individuals with Hypertrophic Cardiomyopathy (HCM). Genetic testing of the disease has been progressively released into the clinical mainstream, thus rendering the development of novel and potent molecular diagnostic protocols an inevitable task. To this direction, we have evolved an integrated PCR-based molecular protocol, which through the utilization of novel "exonic" primers allows, among others, the structural analysis of the 13th exon of the human beta-myosin heavy chain gene locus (MYH7) mainly characterized by the critical for HCM Arginine residue 403 (R(403)). Interestingly, through a DNA sequencing approach, a single nucleotide substitution from "G" to "T" was detected in the adjacent 13th intron, thus divulging the versatile potential of the present molecular protocol to clinical practice.

Cardiovascular genetic medicine: evolving concepts, rationale, and implementation

Cardiovascular genetic medicine is devoted to the identification and understanding of cardiac conditions resulting from genetic and genomic mechanisms and to the development and validation of diagnostic and treatment algorithms and guidelines. Cardiovascular genetic medicine clinics now provide expert cardiovascular subspecialty care, genetic counseling and clinical genetic testing, and will eventually provide disease-specific gene or genetic therapies. Currently, the most tractable diagnoses for cardiovascular genetic medicine are the single-gene disorders: the cardiomyopathies, the channelopathies, and others. The recent explosion of genetic knowledge within the single-gene disorders and consequent rapid proliferation of genetic testing enables far greater numbers of individuals to directly benefit from this progress. A compelling rationale exists for this approach: cardiovascular single-gene diseases commonly present with life-threatening events (e.g., sudden cardiac death, heart failure, stroke, etc.), but identification, evaluation, and treatment of individuals with presymptomatic genetic risk has the promise to prevent or ameliorate cardiovascular morbidity and mortality. Cardiovascular genetic medicine programs also anchor training and research, thereby enabling the next generation of academic specialists in cardiovascular genetic medicine to continue to improve cardiovascular health.

Mutation of junctophilin type 2 associated with hypertrophic cardiomyopathy

Junctophilin subtypes, designated as JPH1 approximately 4, are protein components of junctional complexes and play essential roles in cellular Ca2+ signaling in excitable cells. Knockout mice lacking the cardiac-type Jph2 die of embryonic cardiac arrest, and the mutant cardiac myocytes exhibit impaired formation of peripheral couplings and arrhythmic Ca2+ signaling caused by functional uncoupling between dihydropyridine and ryanodine receptor channels. Based on these observations, we hypothesized that mutations of JPH2 could cause human genetic cardiac diseases. Among 195 Japanese patients (148 index cases and 47 affected family members) with hypertrophic cardiomyopathy (HCM), two heterozygous nonsynonymous nucleotide transitions, G505S and R436C, were newly found in JPH2. When Fisher's exact test was used to compare index cases with HCM to unrelated Japanese healthy controls in the frequencies of mutant alleles, only the G505S mutation showed statistical significance (4/296 HCM patients and 0/472 control individuals, P=0.022). This result was still significant after Bonferroni's correction for multiple comparisons (P=0.044). To the best of our knowledge, this is the first report on JPH2 mutation associated with HCM.

A molecular screening strategy based on beta-myosin heavy chain, cardiac myosin binding protein C and troponin T genes in Italian patients with hypertrophic cardiomyopathy

BACKGROUND

Mutations causing hypertrophic cardiomyopathy (HCM) have been described in nine different genes of the sarcomere. Three genes account for most known mutations: beta-myosin heavy chain (MYH7), cardiac myosin binding protein C (MYBPC3) and cardiac troponin T (TNNT2). Their prevalence in Italian HCM patients is unknown. Thus, we prospectively assessed a molecular screening strategy of these three genes in a consecutive population with HCM from two Italian centres.

METHODS

Comprehensive screening of MYBPC3, MYH7 and TNNT2 was performed in 88 unrelated HCM patients by denaturing high-performance liquid chromatography and automatic sequencing.

RESULTS

We identified 32 mutations in 50 patients (57%); 16 were novel. The prevalence rates for MYBPC3, MYH7 and TNNT2 were 32%, 17% and 2%, respectively. MYBPC3 mutations were 18, including two frameshift, five splice-site and two nonsense. All were 'private' except insC1065 and R502Q, present in three and two patients, respectively. Moreover, E258K was found in 14% of patients, suggesting a founder effect. MYH7 mutations were 12, all missense; seven were novel. In TNNT2, only two mutations were found. In addition, five patients had a complex genotype [i.e. carried a double MYBPC3 mutation (n = 2), or were double heterozygous for mutations in MYBPC3 and MYH7 (n = 3)].

CONCLUSIONS

The first comprehensive evaluation of MYBPC3, MYH7 and TNNT2 in an Italian HCM population allowed a genetic diagnosis in 57% of the patients. These data support a combined analysis of the three major sarcomeric genes as a rational and cost-effective initial approach to the molecular screening of HCM.

Chromosome 1q21.1 contiguous gene deletion is associated with congenital heart disease

Congenital heart disease (CHD), comprising structural or functional abnormalities present at birth, is the most common birth defect in humans. Reduced expression of connexin40 (Cx40) has been found in association with atrial fibrillation, and deletion of Cx40 in a mouse model causes various structural heart abnormalities in 18% of heterozygotes. We screened 505 unrelated CHD cases for deletions or duplications of the Cx40 gene (GJA5) by real-time quantitative PCR, in order to determine whether altered copy number of this gene may be associated with a cardiac phenotype in humans. Dosage of Cx40 flanking genes (ACPL1 and Cx50 gene, GJA8) was determined by real-time PCR for all apparent positive cases. In total, 3 cases were found to carry deletions on chromosome 1q21.1 spanning ACPL1, Cx40, and Cx50 genes. Absence of heterozygosity was observed in all 3 index cases over a 1.5- to 3-Mb region. Samples from the parents of two cases were obtained, and microsatellites across 1q21.1 were genotyped. One of the apparently unaffected parents was found to carry this deletion. All 3 index cases presented with obstruction of the aortic arch as the common structural cardiac malformation, and had no consistent dysmorphic features. Genotyping of 520 unrelated normal controls for this deletion was negative. We hypothesize that this 1q21.1 multigene deletion is associated with a range of cardiac defects, with anomalies of the aortic arch being a particular feature.