Impact of systolic dysfunction in genotyped hypertrophic cardiomyopathy

A case of MYH7 and MYH9 genes variants with cardiomyopathy and macrothrombocytopenia

Key Clinical Message

A 15-year-old girl developed inherited cardiomyopathy and macrothrombocytopenia revealing pathogenic variants of both MYH7 and MYH9 genes. This underlies the importance of repeated genetic testing in diagnosing and managing inherited disorders.

Abstract

The MYH7 and MYH9 genes encode for distinct myosin heavy chain proteins. Our case features a 15-year-old girl, presenting with inherited cardiomyopathy and macrothrombocytopenia, revealing distinct pathogenic variants of both MYH7 and MYH9 genes. This underlines the relevance of genetic testing and personalized medicine in diagnosing and managing inherited disorders.

Personalized medicine for cardiovascular diseases

Personalized medicine is an emerging concept involving managing the health of patients based on their individual characteristics, including particular genotypes. Cardiovascular diseases are heritable traits, and family history information is useful for risk prediction. As such, determining genetic information (germline genetic mutations) may also be applied to risk prediction. Furthermore, accumulating evidence suggests that genetic background can provide guidance for selecting effective treatments and preventive strategies in individuals with particular genotypes. These concepts may be applicable both to rare Mendelian diseases and to common complex traits. In this review, we define the concept and provide examples of personalized medicine based on human genetics for cardiovascular diseases, including coronary artery disease, arrhythmia, and cardiomyopathies. We also provide a particular focus on Mendelian randomization studies, especially those examining loss-of function genetic variations, for identifying high-risk individuals, as well as signaling pathways that may be useful targets for improving healthy living without cardiovascular events.

Syndrome of Primary Myocardial Hypertrophy: Clinical and Morphological, Genetic Diagnostics and Comparison of Sarcomerial Variants of Cardiomyopathy and its Phenocopy

Aim. To study the nosological spectrum in the syndrome of primary left ventricle hypertrophy (PLVH) using morphological and genetic diagnostics and to compare the clinical course of true hypertrophic cardiomyopathy (HCM) and its phenocopy.

Material and methods. Fifty five adult patients (29 men, 48.2±17.0 years) with PLVH (12 mm and more) were included. The exclusion criteria were athletic heart, hypertensive heart disease, severe valvular disease and other causes of secondary left ventricle (LV) hypertrophy. We performed 11 endomyocardial biopsy, 8 intraoperative biopsy, 1 study of explanted heart, 1 autopsy with virus investigation (real-time polymerase chain reaction) of the blood and myocardium. Mutational screening had included simultaneous sequencing of the MYBPC3, TAZ, TPM1, LDB3, MYL2, ACTC1, MYL3, MYH7, TNNI3 and TNNT2 genes based on NGS technology (Ion Torrent PGMTM) with following Sanger resequencing of potentially significant genetic variants. For patients with a phenotype of particular genetic syndrome the Sanger sequencing of target gene(s) for performed first. Clinical examination had included electrocardiography, Holter monitoring, echocardiography, coronary angiography, computer tomography/magnetic resonance imaging (by indication). The mean follow-up was 8 [3;32] month.

Results. Isolated HCM was found in 28 patients, and 10 have a combination of HCM and noncompaction myocardium (NCM). Mutations in the MYH7 and MYBPC3 genes were detected in six cases. In 17 cases (30.9%) the non-sarcomeric causes of LVHS were detected. Three patients had Fabry disease, 2 ‒ had Danon disease, in 10patients we found amyloidoses, in 1 – Friedreich ataxia, and 1 patient was diagnosed with LEOPARD syndrome (all cases were confirmed by DNA diagnostics). Genotype-positive diagnosis was established in 23.6% of patients. In patients with HCM were significantly more frequent asymmetric septal hypertrophy with obstruction and muscle bridges, in other forms of primary hypertrophy – right ventricular hypertrophy, low QRS voltage, QS complexes and increasing of ejection fraction (EF) (55.7±12.5% vs 62.5±10.1% in HCM, p=0.08). The morphologic signs of myocarditis were in 46.7% of patients with HCM detected: in 3 patients with NCM and in 4 patients with isolated HCM. The viral genome in the myocardium was in 11 patients with HCM (73.3%) detected, previously human herpes virus type 6 (it was correlation with myocarditis) and parvovirus B19. Eleven patients died due to a stroke/heart failure without no significant differences between patients with HCM and phenocopy.

Conclusion. The spectrum of causes of the primary left ventricular hypertrophy is very wide. The frequency of myocarditis associated with sarcomeric HCM was 46.7%. When lower EF and heart failure in patients with HCM can be result of myocarditis, in patients with storage disease they are the result of disease itself.

Intrinsic MYH7 expression regulation contributes to tissue level allelic imbalance in hypertrophic cardiomyopathy

HCM, the most common inherited cardiac disease, is mainly caused by mutations in sarcomeric genes. More than a third of the patients are heterozygous for mutations in the MYH7 gene encoding for the β-myosin heavy chain. In HCM-patients, expression of the mutant and the wildtype allele can be unequal, thus leading to fractions of mutant and wildtype mRNA and protein which deviate from 1:1. This so-called allelic imbalance was detected in whole tissue samples but also in individual cells. There is evidence that the severity of HCM not only depends on the functional effect of the mutation itself, but also on the fraction of mutant protein in the myocardial tissue. Allelic imbalance has been shown to occur in a broad range of genes. Therefore, we aimed to examine whether the MYH7-alleles are intrinsically expressed imbalanced or whether the allelic imbalance is solely associated with the disease. We compared the expression of MYH7-alleles in non-HCM donors and in HCM-patients with different MYH7-missense mutations. In the HCM-patients, we identified imbalanced as well as equal expression of both alleles. Also at the protein level, allelic imbalance was determined. Most interestingly, we also discovered allelic imbalance and balance in non-HCM donors. Our findings therefore strongly indicate that apart from mutation-specific mechanisms, also non-HCM associated allelic-mRNA expression regulation may account for the allelic imbalance of the MYH7 gene in HCM-patients. Since the relative amount of mutant mRNA and protein or the extent of allelic imbalance has been associated with the severity of HCM, individual analysis of the MYH7-allelic expression may provide valuable information for the prognosis of each patient.

Prognostic predictive value of gene mutations in Japanese patients with hypertrophic cardiomyopathy

Although some studies have attempted to find useful prognostic factors in hypertrophic cardiomyopathy (HCM), those results are not fully helpful for use in actual clinical practice. Furthermore, several genetic abnormalities associated with HCM have been identified. However, the genotype-phenotype correlation in HCM remains to be elucidated. Here, we attempted to assess patients with different types of gene mutations causing HCM and investigate the prognosis. A total of 140 patients with HCM underwent a screening test for myofilament gene mutations by direct sequencing of eight sarcomeric genes. Patients with a single mutation in cardiac troponin T, cardiac troponin I, α-tropomyosin, and regulatory and essential light chains were excluded from the study because the number of cases was too small. The clinical presentations and outcomes of the remaining 127 patients with HCM, 31 β-myosin heavy chain (MYH7) mutation carriers, 19 cardiac myosin-binding protein C (MYBPC3) mutation carriers, and 77 mutation non-carriers were analyzed retrospectively. MYBPC3 mutation carriers had a high frequency of ventricular arrhythmia and syncope. Kaplan-Meier curves revealed no significant difference in prognosis among the three groups, but a lack of family history of sudden death (SD) and a past history of syncope were significantly related to poor prognosis. An absence of family history of SD and past history of syncope are useful prognostic factors in patients with HCM. MYH7 and MYBPC3 mutations did not significantly influence prognosis compared to non-carriers. However, patients with the MYBPC3 mutation should be closely followed for the possibility of SD.

Whole exome sequencing combined with integrated variant annotation prediction identifies a causative myosin essential light chain variant in hypertrophic cardiomyopathy

BACKGROUND

The development of candidate gene approaches to enable molecular diagnosis of hypertrophic cardiomyopathy (HCM) has required extensive and prolonged efforts. Whole exome sequencing (WES) technologies have already accelerated genetic studies of Mendelian disorders, yielding approximately 30% diagnostic success. As a result, there is great interest in extending the use of WES to any of Mendelian diseases. This study investigated the potential of WES for molecular diagnosis of HCM.

METHODS

WES was performed on seven relatives from a large HCM family with a clear HCM phenotype (five clinically affected and two unaffected) in the Kanazawa University Hypertrophic Cardiomyopathy Registry. Serial bioinformatics filtering methods as well as using combined annotation dependent depletion (CADD) score and high heart expression (HHE) gene data were applied to detect the causative variant. Moreover, additional carriers of the variant were investigated in the HCM registry, and clinical characteristics harboring the variant were collected and evaluated.

RESULTS

WES detected 60020 rare variants in the large HCM family. Of those, 3439 were missense, nonsense, splice-site, or frameshift variants. After genotype-phenotype matching, 13 putative variants remained. Using CADD score and HHE gene data, the number of candidates was reduced to one, a variant in the myosin essential light chain (MYL3, NM_000258.2:c.281G>A, p.Arg94His) that was shared by the five affected subjects. Additional screening of the HCM registry (n=600) identified two more subjects with this variant. Serial assessments of the variant carriers revealed the following phenotypic characteristics: (1) disease-penetrance of 88%; (2) all clinically affected carriers exhibited asymmetric septal hypertrophy with a substantial maximum left ventricular wall thickness of 18±3mm without any obstruction.

CONCLUSIONS

WES combined with CADD score and HHE gene data may be useful even in HCM. Furthermore, the MYL3 Arg94His variant was associated with high disease penetrance and substantial interventricular septal hypertrophy.

Right ventricular hypertrophy is associated with cardiovascular events in hypertrophic cardiomyopathy: evidence from study with magnetic resonance imaging

BACKGROUND

Although left ventricular (LV) morphology and function have been well studied in hypertrophic cardiomyopathy (HCM), few data exist regarding the right ventricle. Accordingly, we studied right ventricular (RV) morphology and function and their effect on cardiovascular events in HCM using cardiac magnetic resonance (CMR) imaging.

METHODS

This retrospective study included 106 HCM patients (age 61.6 ± 14.5 years) examined using CMR imaging during January 2008 to September 2014. RV hypertrophy (RVH) was defined as RV maximal wall thickness > 5 mm.

RESULTS

RVH was observed in 30 of the 106 patients (RVH group), with the remaining 76 patients assigned to the non-RVH group. The RVH group had higher brain natriuretic peptide levels (461.6 ± 699.8 pg/mL vs. 225.3 ± 254.5 pg/mL; P = 0.01) and also showed a reduced RV end-diastolic volume index (43.4 ± 16.0 mL/m2 vs. 56.6±15.2 mL/m2; P = 0.0001), in keeping with a greater LV mass index (109.1 ± 24.9 g/m2 vs. 78.6 ± 23.0 g/m2; P < 0.0001). The RVH group was prominently associated with RV late gadolinium enhancement compared with the non-RVH group (33.3% vs. 0%; P < 0.0001). After CMR imaging, 15 patients developed cardiovascular events that included admission for heart failure, ventricular tachyarrhythmia/fibrillation, stroke, and sudden cardiac death. Cox proportional hazard analysis revealed that RVH was an independent predictor of the occurrence of cardiovascular events after adjustments by sex, age, LV mass index, LV ejection fraction, and LV outflow tract obstruction (hazard ratio, 5.42; 95% confidence interval, 1.16-25.3; P = 0.03).

CONCLUSIONS

These results suggest that HCM patients with RVH on CMR images have a greater incidence of cardiovascular events than non-RVH patients. Further work is needed to confirm this observation and assess its clinical importance.

Increased extent of myocardial fibrosis in genotyped hypertrophic cardiomyopathy with ventricular tachyarrhythmias

BACKGROUND

Occurrence of malignant ventricular tachyarrhythmias such as ventricular tachycardia and fibrillation (VT/VF) in hypertrophic cardiomyopathy (HCM) can be related to the extent of myocardial fibrosis. Although late gadolinium enhancement (LGE) on cardiovascular magnetic resonance (CMR) imaging has been used to detect myocardial fibrosis, few data exist regarding relationships between CMR-determined myocardial fibrosis and VT/VF in genotyped HCM populations.

OBJECTIVE

We retrospectively investigated whether the extent of LGE can be increased in HCM patients with VT/VF compared to those without VT/VF in the genotyped HCM population.

METHODS AND RESULTS

We studied 35 HCM patients harboring sarcomere gene mutations (TNNI3=22, MYBPC3=12, MYH7=1) who underwent both CMR imaging and 24-h ambulatory electrocardiographic monitoring. VT/VF were identified in 6 patients (2 men, mean age 55.0 years). The extent of LGE was significantly increased in patients with VT/VF (n=6) compared with those without VT/VF (n=29) (18.6±14.4% vs. 8.3±11.4%, p=0.04), although the LGE extent was not an independent predictor for the occurrence of VT/VF. Applying a cut-off point ≥3.25%, episodes of VT/VF were identified with a sensitivity of 100%, specificity of 51.7%, positive predictive value of 30%, negative predictive value of 100%, and the area under the curve of 0.767 (95% confidence interval: 0.590-0.944).

CONCLUSION

These results demonstrate that myocardial fibrosis determined by CMR imaging may be increased in genotyped HCM patients with episodes of VT/VF. A further prospective study will be needed to clarify the association between the LGE extent and arrhythmic events in HCM patients harboring sarcomere gene mutations.

Fragmented QRS predicts heart failure progression in patients with hypertrophic cardiomyopathy

BACKGROUND

Although fragmented QRS complex (frag-QRS) reflecting intra-ventricular conduction delay has been shown to be a prognostic marker for cardiac events, few data exist regarding the impact of frag-QRS on cardiac events in hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

Ninety-four HCM patients (56 male; mean age, 58 ± 17 years) were retrospectively investigated. Frag-QRS was defined as the presence of various RsR' patterns in at least 2 contiguous ECG leads. Major arrhythmic events (MAE) were defined as sudden cardiac death, and combined sustained ventricular tachycardia/ventricular fibrillation. New-onset atrial fibrillation (AF) was diagnosed based on ECG during provisional or routine medical examination. Heart failure (HF) with hospitalization was defined as hospital admission due to subjective or objective symptoms. Frag-QRS was detected in 31 patients (33%).TNNI3 was the most frequent disease-causing gene. Median follow-up was 4.6 years. The 4-year cumulative survival rates of cardiac death, MAE, new-onset AF and HF with hospitalization were 97.6%, 94.6%, 87.5% and 89.3%, respectively. On multivariate analysis, frag-QRS was significantly associated with HF with hospitalization (adjusted hazard ratios [95% confidence intervals]: 5.4 [1.2-36], P=0.03). Moreover, HF-free survival was significantly lower in the frag-QRS (+) group compared to the frag-QRS (-) group (79.0% vs. 95.1%, P=0.03).

CONCLUSIONS

Frag-QRS is associated with HF with hospitalization in HCM patients who had a unique distribution of gene mutations.

Compound heterozygosity deteriorates phenotypes of hypertrophic cardiomyopathy with founder MYBPC3 mutation: evidence from patients and zebrafish models

Although most founder mutation carriers of hypertrophic cardiomyopathy (HCM), such as the cardiac myosin-binding protein C gene (MYBPC3), arose from a common ancestor exhibit favorable clinical phenotypes, there still remain small fractions of these carriers associated with increased cardiovascular events. However, few data exist regarding the defining factors that modify phenotypes of these patients, particularly in terms of multiple gene mutations. Therefore, we assessed genotype-phenotype correlations and investigated factors that contribute to phenotypic diversities of mutation carriers from 488 unrelated HCM probands. A prevalent founder mutation (Val762Asp) in MYBPC3 was identified in 33 subjects from 19 families. Among them, 28 carriers harbored an isolated Val762Asp mutation and exhibited a late onset of overt HCM compared with other MYBPC3 mutation carriers (62.8 ± 3.0 vs 50.1 ± 2.6 yr, P < 0.05). In contrast, the remaining five carriers had additional sarcomere gene mutations (3 carriers in MYBPC3 and 2 carriers in the cardiac troponin T gene). Of these five carriers, two carriers showed early disease onset and one carrier exhibited end-stage HCM. These phenotypes were recapitulated in zebrafish models; injection of MYBPC3 Val762Asp alone did not alter ventricular size or function, but ventricular dimension was significantly increased when MYBPC3 Val762Asp mRNA was coinjected with MYBPC3 Arg820Gln mRNA. These results demonstrate that MYBPC3 Val762Asp may be associated with unfavorable HCM phenotypes in some cases when combined with another MYBPC3 mutation.

Significance of sarcomere gene mutations analysis in the end-stage phase of hypertrophic cardiomyopathy

End-stage hypertrophic cardiomyopathy (ES-HC) has an ominous prognosis. Whether genotype can influence ES-HC occurrence is unresolved. We assessed the spectrum and clinical correlates of HC-associated mutations in a large multicenter cohort with end-stage ES-HC. Sequencing analysis of 8 sarcomere genes (MYH7, MYBPC3, TNNI3, TNNT2, TPM1, MYL2, MYL3, and ACTC1) and 2 metabolic genes (PRKAG2 and LAMP2) was performed in 156 ES-HC patients with left ventricular (LV) ejection fraction (EF) <50%. A comparison among mutated and negative ES-HC patients and a reference cohort of 181 HC patients with preserved LVEF was performed. Overall, 131 mutations (36 novel) were identified in 104 ES-HC patients (67%) predominantly affecting MYH7 and MYBPC3 (80%). Complex genotypes with double or triple mutations were present in 13% compared with 5% of the reference cohort (p = 0.013). The distribution of mutations was otherwise indistinguishable in the 2 groups. Among ES-HC patients, those presenting at first evaluation before the age of 20 had a 30% prevalence of complex genotypes compared with 19% and 21% in the subgroups aged 20 to 59 and ≥60 years (p = 0.003). MYBPC3 mutation carriers with ES-HC were older than patients with MYH7, other single mutations, or multiple mutations (median 41 vs 16, 26, and 28 years, p ≤0.001). Outcome of ES-HC patients was severe irrespective of genotype. In conclusion, the ES phase of HC is associated with a variable genetic substrate, not distinguishable from that of patients with HC and preserved EF, except for a higher frequency of complex genotypes with double or triple mutations of sarcomere genes.

Detection of mutations in symptomatic patients with hypertrophic cardiomyopathy in Taiwan

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a common genetic cardiac disorder associated with sudden death, heart failure, and stroke. The aim of the present study was to evaluate the prevalence and types of mutations in symptomatic patients with HCM in Taiwan.

METHODS

Thirty-eight HCM index patients (mean age 60±16 years) underwent systematic mutation screening of eight sarcomeric genes: β-myosin heavy chain (MYH7), myosin-binding protein C (MYBPC3), troponin T (TNNT2), troponin I (TNNI3), myosin ventricular regulatory light chain 2 (MYL2), myosin ventricular essential light chain 1 (MYL3), α-tropomyosin (TPM1), and cardiac α-actin (ACTC), using direct DNA sequencing. In silico programs predicted damaging amino acids. In the positive families, genotype-phenotype correlation studies were done.

RESULTS

Overall, 13 mutations were identified in 13 index patients (34.2%). The three most frequently mutated genes were MYH7, MYBPC3, and TNNT2. One patient carried double mutations. Five mutations (MYH7 R147S; MYBPC3 R597Q; MYBPC3 W1007R; TNNI3 E124Q; MYL3 R63C) were novel; all were missense mutations. Analysis using in silico tools showed near consensus to classify these five novel mutations as pathological. Family pedigree analysis showed the presence of cosegregation in at least two affected members in each proband family, but incomplete penetrance in young family members with a positive genotype.

CONCLUSIONS

We identified 13 HCM pedigrees, including 5 carrying novel mutations and 1 with a double mutation. The three most commonly mutated genes were MYH7, MYBPC3, and TNNT2. These results, together with genetic counseling, could lead to earlier diagnosis and better management of family members at risk of HCM.

Current perspectives in genetic cardiovascular disorders: from basic to clinical aspects

We summarize recent advances in the clinical genetics of hypercholesterolemia, hypertrophic cardiomyopathy (HCM), and lethal arrhythmia, all of which are monogenic cardiovascular diseases being essential to understanding the heart and circulatory pathophysiology. Among the issues of hypercholesterolemia which play a pivotal role in development of vascular damages, familial hypercholesterolemia is the common genetic cardiovascular disease; in addition to identifying the gene mutation coding low-density lipoprotein receptor, lipid kinetics in autosomal recessive hypercholesterolemia as well as in proprotein convertase subtilisin/kexin 9 gene mutation were recently demonstrated. As for HCM, some gene mutations were identified to correlate with clinical manifestations. Additionally, a gene polymorphism of the renin-angiotensin system in development of heart failure was identified as a modifier gene. The lethal arrhythmias such as sudden death syndromes, QT prolongation, and Brugada syndrome were found to exhibit gene mutation coding potassium and/or sodium ion channels. Interestingly, functional analysis of these gene mutations helped to identify the role of each gene mutation in developing these cardiovascular disorders. We suggest considering the genetic mechanisms of cardiovascular diseases associated with hyperlipidemia, myocardial hypertrophy, or lethal arrhythmia in terms of not only clinical diagnosis but also understanding pathophysiology of each disease with therapeutic aspects.