Familial Hypertrophic Cardiomyopathy: Diagnosis and Management.

Hypertrophic cardiomyopathy (HCM) is widely recognized as one of the most common inheritable cardiac disorders. Since its initial description over 60 years ago, advances in multimodality imaging and translational genetics have revolutionized our understanding of the disorder. The diagnosis and management of patients with HCM are optimized with a multidisciplinary approach. This, along with increased safety and efficacy of medical, percutaneous, and surgical therapies for HCM, has afforded more personalized care and improved outcomes for this patient population. In this review, we will discuss our modern understanding of the molecular pathophysiology that underlies HCM. We will describe the range of clinical presentations and discuss the role of genetic testing in diagnosis. Finally, we will summarize management strategies for the hemodynamic subtypes of HCM with specific emphasis on the rationale and evidence for the use of implantable cardioverter defibrillators, septal reduction therapy, and cardiac myosin inhibitors.

Investigating the Pathogenesis of MYH7 Mutation Gly823Glu in Familial Hypertrophic Cardiomyopathy using a Mouse Model.

Familial hypertrophic cardiomyopathy (HCM, OMIM: 613690) is the most common cardiomyopathy in China. However, the underlying genetic etiology of HCM remains elusive. We previously identified a myosin heavy chain 7 (MYH7) gene heterozygous variant, NM_000257.4: c.G2468A (p.G823E), in a large Chinese Han family with HCM. In this family, variant G823E cosegregates with an autosomal dominant disorder. This variant is located in the lever arm domain of the neck region of the MYH7 protein and is highly conserved among homologous myosins and species. To verify the pathogenicity of the G823E variant, we produced a C57BL/6N mouse model with a point mutation (G823E) at the mouse MYH7 locus with CRISPR/Cas9-mediated genome engineering. We designed gRNA targeting vectors and donor oligonucleotides (with targeting sequences flanked by 134 bp of homology). The p.G823E (GGG to GAG) site in the donor oligonucleotide was introduced into exon 23 of MYH7 by homology-directed repair. A silenced p.R819 (AGG to CGA) was also inserted to prevent gRNA binding and re-cleavage of the sequence after homology-directed repair. Echocardiography revealed left ventricular posterior wall (LVPW) hypertrophy with systole in MYH7 G823E/- mice at 2 months of age. These results were likewise validated by histological analysis (Figure 3). These results demonstrate that the G823E variant plays an important role in the pathogenesis of HCM. Our findings enrich the spectrum of MYH7 variants linked to familial HCM and may provide guidance for genetic counseling and prenatal diagnosis in this Chinese family.

MicroRNA expression profiles in familial hypertrophic cardiomyopathy with myosin-binding protein C3 (MYBPC3) gene mutations.

Familial hypertrophic cardiomyopathy (FHCM) is an autosomal dominant inherited disease caused by mutations in genes encoding cardiac sarcomere proteins. MicroRNAs (miRNAs) play an important role in the pathogenesis of FHCM. In the present study, we aimed to determine the miRNA profile in FHCM patients with myosin-binding protein C3 (MYBPC3) gene mutations. We recruited three FHCM patients and age- and sex-matched controls. The three probands all had hypertrophic obstructive cardiomyopathy with severe myocardial hypertrophy, and two of the three had a history of sudden cardiac death, representing a "malignant" phenotype. We then compared the miRNA expression profiles of three FHCM patients carrying MYBPC3 gene mutations with those of the normal control group using miRNA sequencing technology. Differentially expressed miRNAs were verified using real-time polymerase chain reaction (qPCR). Target genes and signaling pathways of the identified differentially expressed miRNAs were predicted using bioinformatics analysis. A total of 33 significantly differentially expressed miRNAs were detected in the peripheral blood of the three probands, of which 28 were upregulated, including miR-208b-3p, and 5 were downregulated. Real-time PCR confirmed the upregulated expression of miR-208b-3p in FHCM patients (P < 0.05). Bioinformatics analysis showed that miR-208b-3p was mainly enriched in 79 target genes including UBE2V2, MED13, YBX1, CNKSR2, GATA4, andSOX5/6, et al. Gene ontology (GO) analysis of target genes showed that miR-208b was mainly involved in the processes of negative regulation of transcription from RNA polymerase II promoter, and regulation of transcription, DNA templated. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the target genes regulated by miR-208b-3p were mainly involved in the Wnt signaling pathway. These findings suggest that FHCM patients with MYBPC3 gene mutations have a specific miRNA expression profile, and that miR-208b-3p is significantly upregulated in cardiac hypertrophy. Our results also indicate that miRNA-208b-3p activates the Wnt signaling pathway through its target gene to promote cardiac hypertrophy.

Hypertrophic Cardiomyopathy in Pregnancy.

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiac condition and highly heterogeneous. Echocardiography and genetic and clinical screening have led to detection in women of childbearing age. Maternal and fetal outcomes among women with HCM are favorable. Genetic counseling is recommended. Prepregnancy clinical evaluation and risk assessment are paramount in ensuring optimal outcomes. Most women carry moderate risk of morbidity, have clinical evaluations and echocardiography each trimester, and deliver vaginally. Those who are symptomatic or have significant left ventricular outflow obstruction or recurrent arrhythmias prior to pregnancy are at higher risk and should be monitored at least monthly.

Gap junction protein beta 4 plays an important role in cardiac function in humans, rodents, and zebrafish.

AIMS: GJB4 encodes a transmembrane connexin protein (Cx30.3) that is a component of gap junctions. This study investigated whether GJB4 plays an important role in human heart disease and function. METHODS AND RESULTS: We examined a patient and her older brother who both presented with complicated severe hypertrophic cardiomyopathy (HCM) and whose parents are healthy married cousins. The gene exome analysis showed 340 single nucleotide polymorphisms (SNPs) that caused amino acid changes for which the patient was homozygous and both parents were heterozygous. After excluding all known common (>10%) SNP gene mutations, the gene for GJB4 was the only identified gene that is possibly associated with cardiac muscle. The resultant E204A substitution exists in the 4th transmembrane domain. GJB4-E204A impaired the binding with gap junction protein A1 (GJA1) compared with GJB4-WT. The expression of GJB4 was induced in rat disease models of left and right ventricle hypertrophy and mouse disease models of adriamycin-induced cardiomyopathy and myocardial infarction, while it was not detected at all in control. An immunohistochemical study was performed for autopsied human hearts and the explanted heart of the patient. GJB4 was expressed and colocalized with GJA1 in intercalated discs in human diseased hearts, which was extensively enhanced in the explanted heart of the patient. The abnormal expression and localization of GJB4 were observed in beating spheres of patient's induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs). We generated knockout zebrafish of GJB4 by CRISPR/Cas9 and the endodiastolic volume and the ventricular ejection fraction were significantly lower in GJB4-deficient than in wild-type zebrafish at five days post-fertilization. CONCLUSIONS: These results indicate both that GJB4 is defined as a new connexin in diseased hearts, of which mutation can cause a familial form of HCM, and that GJB4 may be a new target for the treatment of cardiac hypertrophy and dysfunction.

A novel nonsense mutation in TNNT2 in a Chinese pedigree with hypertrophic cardiomyopathy: A case report.

RATIONALE: Hypertrophic cardiomyopathy (HCM) is an inherited myocardial disease and a common cause of sudden cardiac death, heart failure, atrial fibrillation and stroke. In families affected by HCM, genotyping is useful for identifying susceptible relatives. In the present study, we investigated the disease-causing mutations in a three-generation Chinese family with HCM using whole exome sequencing (WES). PATIENT CONCERNS: The proband, a 50-year-old man, was diagnosed with HCM at the age of 41 years. He presented with an asymmetric hypertrophic interventricular septum and a maximum interventricular septum thickness of 18.04 mm. His third elder sister, niece and daughter were also clinically affected by HCM. DIAGNOSIS: Autosomal dominant HCM. INTERVENTIONS: Seven family members, including 4 affected members, accepted WES. The genetic variants were subsequently called using Genome Analysis Toolkit and annotated using the InterVar program. Following frequency filtration by the Genome Aggregation Database, the variants were evaluated using an in-house bioinformatics analysis pipeline. OUTCOMES: HCM was transmitted as an autosomal dominant trait in the family. An extremely rare stop gained mutation, rs796925245 (g.1:201359630G>A, c.835C>T, p.Gln279Ter) in the troponin T2 (TNNT2) gene was identified as the disease-causing mutation. The stop gained mutation was predicted to result in a truncated troponin T protein in cardiac sarcomere. An adolescent family member who had normal echocardiographic measurements was found to carry the same disease-causing mutation. LESSONS: A novel nonsense TNNT2 mutation was identified as the HCM-causing mutation in this Chinese pedigree. Since HCM shows a low penetrance by clinical criteria in adolescents, the adolescent mutation carrier, who is still clinically unaffected, should be offered routine follow-ups and sport activity recommendations to prevent adverse events including sudden cardiac death in the future.

Significance of Pulmonary Hypertension in Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is the most prevalent hereditary cardiac disease characterized by the presence of left ventricular and/or septal hypertrophy in the absence of other underlying cardiac disorders. Patients of HCM have a broad range of clinical presentation from being asymptomatic to severely ill condition requires hospitalization and urgent management. Broadly, HCM is classified in two variants: obstructive and nonobstructive. The mainstay of diagnosis is through echocardiography. As HCM chiefly affect the left heart, pulmonary hypertension (PH) is an expected complication of this disease. Though the existence of PH in HCM is known for a long time, its clinical significance, underlying mechanism, and prognostic impact in HCM have been revealed by few recent studies. Specifically, studies have shown increased events of thromboembolism, atrial fibrillation, and heart failure in patients with HCM and PH. These studies elucidated the underlying mechanism of PH in HCM--a rise of pressure in the precapillary and postcapillary pulmonary vasculature. In addition to left ventricular involvement, studies have shown right ventricular involvement and the association of left and right ventricular dysfunction in these patients. Further, it has been shown that surgical intervention to reduce septal thickness improves survival in pharmacotherapy nonresponders and the presence of PH does not increase mortality in these patients. We present a comprehensive review exploring the prevalence, underlying mechanisms, and impact of PH on HCM.

MYH7 Gene-Related Mutation p.V878L Identified in a Chinese Family with Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is one of the most common inherited cardiovascular diseases and possesses a high risk for sudden cardiac death. Although mutations in more than 20 genes have been reported to be associated with HCM thus far, the genetic backgrounds of most HCM patients are not fully understood. We performed a genetic analysis in a Chinese family that presented with HCM using next-generation sequencing (NGS). Clinical data, family histories, and blood samples were collected from the proband and family members. Five patients showed typical clinical symptoms of HCM. One subject was the victim of sudden cardiac death. By NGS, we determined that these subjects with HCM symptoms carried a missense heterozygous genetic mutation c.2632C>A (p.V878L) in the myosin heavy chain 7 (MYH7) gene with an autosomal dominant pattern of inheritance. Individuals without this mutation showed no symptoms or cardiac structural abnormalities related to HCM. Bioinformatics evaluation predicted this mutant as "damaging" and "disease causing". Additionally, sequence alignment showed that this mutant is located in an evolutionarily conserved region of MYH7 in multiple species. Our results describe a potentially pathogenic mutation associated with HCM, which may extend the spectrum of HCM phenotypes related to MYH7 gene mutations.

Genetic analysis of monoallelic double MYH7 mutations responsible for familial hypertrophic cardiomyopathy.

ß­myosin heavy chain (MHC) 7 (MYH7) is the dominant pathogenic gene that harbors mutations in 20­30% of cases of familial hypertrophic cardiomyopathy (HCM). The aim of this study was to elucidate the distribution and type of genetic variations among Chinese HCM families. From 2013 to 2017, the clinical data of 387 HCM probands and their families were collected. Targeted exome­sequencing technology was used in all probands, and the selected mutations were subsequently verified by Sanger sequencing in the probands, family members and 300 healthy ethnic­matched volunteers. Three­dimensional models were created using Swiss­PdbViewer 4.1, and further genetic analyses were performed to determine sequence conservation and frequency of the mutations. Among the 5 probands with double MYH7 mutations, 4 carried compound heterozygous mutations, and 1 carried monoallelic double mutations (A934V and E1387K). Four family members of the proband with monoallelic double mutations had the same mutation as the proband. Echocardiography and 12­lead electrocardiography revealed abnormalities in the proband and 3 of the 4 carriers. The probands with compound heterozygous mutation had a higher left ventricular mass as revealed by echocardiography and higher QRS, SV1 and RV5+SV1 amplitudes than those with monoallelic double mutations (P<0.05). Simulation of the 3D structure of mutated proteins showed that the replacement of alanine by valine affected the flexibility of the MHC neck domain in case of the A934V mutation, whereas reactivity of the MHC rod domain was affected in the case of the E1387K mutation. In conclusion, we identified several novel HCM­causing MYH7 mutations. More importantly, this is the first study to report a rare HCM family with monoallelic double mutations.

A novel LAMP2 p.G93R mutation associated with mild Danon disease presenting with familial hypertrophic cardiomyopathy.

BACKGROUND: Danon disease (DD) is an X-linked dominant multisystem disorder that is associated with cardiomyopathy, skeletal myopathy, and varying degrees of intellectual disability. It results from mutations in the lysosome-associated membrane protein 2 (LAMP2) gene. METHODS: Herein, a proband with a mild DD case presenting with a familial hypertrophic cardiomyopathy (HCM) phenotype and additional family members were evaluated. Exome sequencing and Sanger sequencing were performed to explore the genetic basis of DD in the proband. Segregation, in silico, and functional analyses were carried out to explore potential pathogenicity in the candidate mutation. RESULTS: Exome sequencing and Sanger sequencing identified one novel missense mutation (p.G93R) in the LAMP2 gene in the proband, and this mutation was also identified in three other family members. In silico analysis of LAMP2 predicted that the mutation causes a conformational change and subsequent protein destabilization. Furthermore, functional examination showed that mutation carriers have a significant reduction in LAMP2 expression, which supports that the mutation is pathogenic. Moreover, skewed X chromosome inactivation (XCI) was identified in one female mutation carrier, thus suggesting that skewed XCI may be the reason why this individual escaped the pathogenic influence of the mutation. CONCLUSION: These findings will aid in diagnosing DD patients carrying this LAMP2 mutation that presents with a HCM phenotype. Furthermore, this study illustrates the importance of utilizing a molecular diagnostic approach in HCM patients and is the first study to report a LAMP2 p.G93R mutation associated with mild DD and identify that XCI serves a protective role in DD etiology.

Long-Term Follow-Up of Idiopathic Ventricular Fibrillation in a Pediatric Population: Clinical Characteristics, Management, and Complications.

Background The natural history and long-term outcome in pediatric patients with idiopathic ventricular fibrillation ( IVF ) are poorly characterized. We sought to define the clinical characteristics and long-term outcomes of a pediatric cohort with an initial diagnosis of IVF . Methods and Results Patients were included from an International Registry of IVF (consisting of 496 patients). Inclusion criteria were: (1) VF with no identifiable cause following comprehensive analysis for ischemic, electrical or structural heart disease and (2) age ≤16 years. These included 54 pediatric IVF cases (age 12.7±3.7 years, 59% male) among whom 28 (52%) had a previous history of syncope (median 2 syncopal episodes [interquartile range 1]). Thirty-six (67%) had VF in situations associated with high adrenergic tone. During a median 109±12 months of follow-up, 31 patients (57%) had recurrence of ventricular arrhythmias, mainly VF . Two patients developed phenotypic expression of an inherited arrhythmia syndrome during follow-up (hypertrophic cardiomyopathy and long QT syndrome, respectively). A total of 15 patients had positive genetic testing for inherited arrhythmia syndromes. Ten patients (18%) experienced device-related complications. Three patients (6%) died, 2 due to VF storm. Conclusions In pediatric patients with IVF , a minority develop a definite clinical phenotype during long-term follow-up. Recurrent VF is common in this patient group.

Anterior myocardial infarction in a patient with isolated left ventricular non-compaction.

We presented a 55-year-old male patient with isolated left ventricular non-compaction who was admitted to our emergency department for chest pain and exertional dyspnoea. He was hospitalised due to anterior myocardial infarction, and during his assessment, isolated left ventricular non-compaction was diagnosed.

Next-generation sequencing (NGS) as a molecular diagnostic tool for hypertrophic cardiomyopathy in a Chinese boy due to novel compound heterozygous mutations in the MYBPC3 gene: A case report.

RATIONALE: Hypertrophic cardiomyopathy (HCM) is mainly caused by mutations in genes encoding sarcomeric proteins. One of the most commonly mutated HCM genes is the MYBPC3 gene. Mutations in this gene lead mainly to truncation of the protein, which gives rise to a relatively severe phenotype. Analyses of gene mutations associated with HCM are valuable for molecular diagnosis, genetic counseling, and management of familial HCM. PATIENT CONCERNS: A 12-year-old boy presented with palpitations and dyspnea after exercise for 1 year. Echocardiography showed myocardial asymmetric hypertrophy of the ventricular septum, the anterior wall, and the lateral wall of the left ventricle. The thickness of the interventricular septum was estimated to be 33 mm. ECG showed left ventricular high voltage and ST-T changes. He had been diagnosed with HCM 3 months previously. DIAGNOSES: Due to his clinical presentation, he was determined to have HCM via a molecular analysis, revealing compound heterozygotes (p.R597W and p.Q1012Sfs*8) in the MYBPC3 gene. INTERVENTIONS: The patient was prescribed metoprolol to slow the heart rate and increase diastolic filling time. OUTCOMES: The boy was treated with metoprolol 6.75 mg b.i.d. Approximately 3 months later, review of the echocardiography showed that the peak velocity across the LVOT dropped to 2.3 m/seconds and that the pressure gradient dropped to 21 mm Hg. LESSONS: A custom next-generation sequencing (NGS) technology for the HCM panel allowed us to identify compound heterozygous mutations in the MYBPC3 gene, confirming NGS as a molecular diagnostic tool.

Different Clinical Presentation and Tissue Characterization in a Monozygotic Twin Pair with MYH7 Mutation-Related Hypertrophic Cardiomyopathy.

This case report demonstrates a pair of monozygotic twins with hypertrophic cardiomyopathy (HCM) carrying the same pathogenic mutation of MYH7 (p.G768R; c.2302G>A), detected by whole exome and Sanger genetic sequencing methods. On multi-modality imaging, they were reported to have similar, but not identical, morphologic expression. Particularly, the clinical presentation and tissue characteristics were not the same. Late gadolinium enhancement (LGE) and T1 mapping of cardiac magnetic resonance showed different extents of myocardial fibrotic characteristics in the twins (twin A: 16.3% LGE and 32.6% extracellular volume [ECV] of the whole left ventricle; twin B: 5.4% LGE and 28.1% ECV of the whole left ventricle). This extraordinary case of HCM provides evidence on the complex pathophysiological mechanisms of HCM and suggests the likely impact of epigenetics and environmental factors on HCM phenotype.

Evaluating the Clinical Validity of Hypertrophic Cardiomyopathy Genes.

BACKGROUND: Genetic testing for families with hypertrophic cardiomyopathy (HCM) provides a significant opportunity to improve care. Recent trends to increase gene panel sizes often mean variants in genes with questionable association are reported to patients. Classification of HCM genes and variants is critical, as misclassification can lead to genetic misdiagnosis. We show the validity of previously reported HCM genes using an established method for evaluating gene-disease associations. METHODS: A systematic approach was used to assess the validity of reported gene-disease associations, including associations with isolated HCM and syndromes including left ventricular hypertrophy. Genes were categorized as having definitive, strong, moderate, limited, or no evidence of disease causation. We also reviewed current variant classifications for HCM in ClinVar, a publicly available variant resource. RESULTS: Fifty-seven genes were selected for curation based on their frequent inclusion in HCM testing and prior association reports. Of 33 HCM genes, only 8 (24%) were categorized as definitive ( MYBPC3, MYH7, TNNT2, TNNI3, TPM1, ACTC1, MYL2, and MYL3); 3 had moderate evidence ( CSRP3, TNNC1, and JPH2; 33%); and 22 (66%) had limited (n=16) or no evidence (n=6). There were 12 of 24 syndromic genes definitively associated with isolated left ventricular hypertrophy. Of 4191 HCM variants in ClinVar, 31% were in genes with limited or no evidence of disease association. CONCLUSIONS: The majority of genes previously reported as causative of HCM and commonly included in diagnostic tests have limited or no evidence of disease association. Systematically curated HCM genes are essential to guide appropriate reporting of variants and ensure the best possible outcomes for HCM families.

The False-negative Phenotype.

Ethical controversies may arise when genome sequencing reveals a genetic variant that is thought to be pathogenic, but the patient has no symptoms. This could be due to variable penetrance or expressivity. It could also result from a misclassification of the gene as pathogenic. In this article, I analyze 2 possibilities when such a situation occurs. The first is straightforward. We could conclude that the sequencing results should be considered a "false-positive" test result. The second is a bit more counterintuitive. In some cases, we could consider the test result to be a true-positive but in way that has not yet led to phenotypic findings. Somewhat playfully, we imagine that, in such cases, we could consider the patient's phenotype to be falsely negative. Sometimes, as odd as it seems, we act is if that is what we believe.

Insights Into Hypertrophic Cardiomyopathy Evaluation Through Follow-up of a Founder Pathogenic Variant.

INTRODUCTION AND OBJECTIVES: Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease. The current challenge relies on the accurate classification of the pathogenicity of the variants. Transthoracic echocardiography (TTE) is recommended at initial evaluation and cardiac magnetic resonance (CMR) imaging should also be considered. We aimed to reappraise the penetrance and clinical expression of the MYBPC3 p.G263* variant. METHODS: Three hundred and eighty-four HCM probands and a control cohort of 450 individuals were studied for the main sarcomere genes by next-generation sequencing. All MYBPC3 p.G263* carriers were identified and family screening was performed. Clinical information was recorded retrospectively before 2015 and prospectively thereafter. Extra effort was invested in performing CMR in all carriers, despite TTE results. RESULTS: Thirteen HCM probands and none of the controls were carriers of the MYBPC3 p.G263* pathogenic variant (according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology). A total of 39 carriers were identified with family screening. Most patients with HCM were asymptomatic at the time of diagnosis and showed late-onset disease. Despite having a relatively benign course in the young, late HCM-related complications could occur. Penetrance was around 70% when evaluated by TTE and was 87.2% with TTE plus CMR. Penetrance was age-dependent, reaching 100% in carriers older than 55 years. CONCLUSIONS: MYBPC3 p.G263* shares with most truncating pathogenic variants in this gene a late onset, relatively benign clinical course in the young, and high penetrance. Cardiac magnetic resonance could be a useful tool to evaluate carriers despite TTE results.

[Gene screening and phenotype analysis in a pedigree with familial hypertrophic cardiomyopathy from Yunnan Province].

Objective: To identify the disease-causing mutations in a pedigree with familial hypertrophic cardiomyopathy (HCM) from Yunnan province, and analyze the relationship between the genotype and the phenotype. Methods: The blood samples and the clinical data of the HCM family members were collected.The coding exons and their flanking intronic regions of 28 previously reported genes related to HCM were screened in the proband by high-throughput sequencing. The mutations in proband were confirmed and detected in all family members as well as in 159 healthy controls by Sanger sequencing.The relationship between the genotype and the phenotype was analyzed in this pedigree. Results: Two missense mutations of Arg1045His and Ala26Val in ß myosin heavy chain gene(MYH7) were identified. Genetic screening showed that the mother and brother of the proband carried Arg1045His mutation.Both mutations were absent in other family members and in 159 healthy controls.Disease onset age was less than 50 years old in this pedigree, chest pain, exertional dyspnea and syncope were the major symptoms, and all accompanied by severe left ventricular hypertrophy and left ventricular outflow tract stenosis.The grandma of the proband suffered sudden cardiac death. The proband had the worst symptoms and the earliest disease onset in this pedigree. Conclusions: We find a pedigree with familial HCM from Yunnan province carrying MYH7 Arg1045His and Ala26Val mutations. The study suggests that Arg1045His mutation in MYH7 gene caused HCM is malignant with early onset, severe ventricular hypertrophy and poor prognosis. Arg1045His and Ala26Val double-mutant might have dosage effects and aggravate the clinical phenotype of the patient.