Mutations In Sarcomeric Genes Research Articles

503 SPECKLE-TRACKING ECHOCARDIOGRAPHY FOR ARRHYTHMIC RISK ASSESSMENT IN HYPERTROPHIC AND FABRY CARDIOMYOPATHY

Abstract Background Hypertrophic Cardiomyopathy (HCM) is burdened by sudden cardiac death (SCD) risk of 0.9%/year, and is the most common cause of SCD in young adults. It is an autosomal dominant inherited disease caused by mutations in cardiac sarcomere genes, but the hypertrophic phenotype can also be an expression of cardiac involvement in multiorgan metabolic storage diseases, such as Anderson-Fabry disease (AFD). Mechanical Dispersion (MD) by Speckle-Tracking Echocardiography (STE) has recently emerged as an additional arrhythmic risk marker. Purpose Aim of the study was to evaluate LV systolic and diastolic function, global longitudinal strain (GLS) and MD by STE and analyze their association with ventricular arrhythmias in patients with HCM and AFD. Methods We included in our analysis 36 patients with HCM, 54 with AFD, of which 10 with left ventricular hypertrophy (AFD-LVH) and 44 without (AFD-N), and 27 healthy subjects. We performed a comprehensive basic echocardiographic study and analyzed GLS and MD (post-processing through EchoPAC 2.02). We also evaluated ventricular arrhythmias (V-AR), including ventricular fibrillation and sustained and non-sustained ventricular tachycardia, by Holter ECG, and the data obtained by cardiac magnetic resonance (CMR) in hypertrophic patients. Data were analyzed by unpaired Student t-test or chi-square/Fisher's exact test as appropriate, and binary logistic regression (SPSS Statistics ver.26). Results Diastolic function was impaired in HCM and AFD-LVH patients compared to control and AFD without LVH. GLS was significantly lower in the V-AR group compared to patients without V-AR (9.7±2.9 vs 14.1±4, P=0.007), MD was significantly higher in the V-AR group (111±47 vs 68.1±16, P=0.03). We found a significant association between ventricular arrhythmias and GLS (P=0.005) and between ventricular arrhythmias and MD (P<0.001). We found also a significant association of late gadolinium enhancement at CMR with GLS (P=0.005) and MD (P=0.03). Conclusions GLS and MD are useful additional indices in the evaluation of patients with HCM or AFD, also in presence of preserved LV ejection fraction, and promising prognostic predictors to identify patients at high risk for ventricular arrhythmias Figures: MD in an HCM patient (on the left) and in an AFD-LVH patient (on the right).

A novel mutation in the tropomyosin 1 gene in a Chinese patient with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an inherited heart disease characterized by left ventricular hypertrophy. Although sarcomeric gene mutations can explain many HCM cases, the genetic basis of approximately half of HCM cases remains elusive. Here, we report the case of a 30-year-old woman with HCM after imaging and pathological examinations. We identified a novel mutation in a pathogenic gene from the HCM patient through whole-exome sequencing. A heterozygous missense mutation in exon 1 of the α-tropomyosin (TPM1) gene (NM_000366.5:exon1:c.71A > G) was found based on patient sequencing data. The mutation resulted in glutamine replacing arginine (p.Gln24Arg). This mutation was expected to cause significant and deleterious changes in the structure of the TPM1 protein. Therefore, according to pathogenicity assessment guidelines, the mutation was considered likely pathogenic. We found that most of these mutations are related to cardiomyopathy and majority of them are in exon 1 and are missense mutations. TPM1 mutations are thus a common cause of HCM and other congenital heart defects. Thus, a novel missense variant, p.Gln24Arg, in the TPM1 gene is associated with the autosomal dominant disease HCM. These results expand the knowledge spectrum of TPM1 gene function.

Abstract 10925: A Small Molecule Inhibitor of Sarcomere Contractility Acutely Relieves Prolonged Relaxation in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes With Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is one of the most common genetic cardiac diseases primarily caused by mutations in sarcomeric genes. However, HCM is also associated with mutations in non-sarcomeric proteins and a Finnish founder mutation for HCM in non-sarcomeric protein junctophilin-2 (JPH2) has been identified. MYK-461 is a recently described mechanistically novel small molecule that acts at the sarcomere to specifically inhibit contractility that has been proposed as a treatment for HCM. Here, we use MYK-461 to test whether direct reduction in contractility is sufficient to relieve phenotypic characteristics in human-induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) carrying JPH2 mutation T161K. Hypothesis: Currently all HCM patients are treated the same regardless of the underlying genetic defect. Current medication does not prevent or stop the thickening of the heart muscle; only the symptoms and arrhythmias can be controlled with beta-blockers or calcium blockers. MYK-461 decreases adenosine triphosphatase activity of the cardiac myosin heavy chain to reduce contractility, thus modifying the characteristic pathology of HCM. Methods: Skin fibroblasts from a Finnish patient with HCM causing JPH2 p.(Thr161Lys) were reprogrammed into hiPSCs and further differentiated into CMs. As a control line, an isogenic counterpart was generated using the CRISPR/Cas9 genome editing method. We evaluated the effect of MYK-461 treatment to T161K-hiPSC-CMs by their functional characteristics associated with JPH2 mutation. Results: By video microscopy, we identified increased contractility (BPM; 41±6 SEM, n=9) and prolonged diastolic phase (ms; 394.8±29.7 SEM, n=9) in T161K-hiPSC-CMs. Treatment with MYK-461 reduced contractility (BPM; 36±3 SEM, n=10) and relaxation phase (ms; 293.1±33.6 SEM, n=10) in a dose-dependent manner, displaying functional characteristics closer to isogenic-hiPSC-CMs control group. Conclusions: In conclusion, the results demonstrate that acute reduction in contractility is sufficient to relieve prolonged relaxation. Further, these studies suggest that T161K-hiPSC-CMs provide adequate in vitro platform for modelling the functional effect of MYK-461.

Genotype-phenotype correlation and allele dating analysis of a novel variant in hypertrophic cardiomyopathy: p.Arg652Lys in MYH7

Abstract Background/Introduction Hypertrophic cardiomyopathy (HCM) is a genetic disease characterised by increased left ventricle (LV) wall thickness caused by mutations in sarcomeric genes. Finding a causal mutation can help to better assess the proband's risk, as it allows the presence of the mutation to be evaluated in relatives and the follow-up to be focused on carriers. Purpose The objectives of the present study are to assess the genotype-phenotype correlation of a novel variant found in patients with HCM and explore the possibility of a founder effect in the Balearic Islands, Spain. Methods We performed an observational study with phenotype description and genotype correlation of patients with HCM in whom we found a novel variant in the MYH7 gene (NM_000257.4:c.1955G>A) which putatively causes a p.Arg652Lys missense protein change. We did IBD/coalescent-based allele dating analysis of this novel variant. Results This previously non-described variant was found in twelve families with HCM. Out of those, 59 patients corresponding to 8 families were clinically characterized with a median follow-up of 63 months. Among them, 39 (66%) carry the variant. Twenty-five (64%) of carriers developed HCM. A median maximum LV wall thickness of 16.5 mm was described. The LV hypertrophy was asymmetric septal in 75% of cases, with LV outflow tract obstruction in 28%. The incidence of a composite of serious adverse cardiovascular events (sudden death, aborted sudden death, appropriate implantable cardiac defibrillator dis-charge, an embolic event, or admission for heart failure) was observed in five (20%) patients. This p.Arg652Lys variant was classified as likely pathogenic (LP) and associated with the development of HCM for the following reasons: 1) It is found in patients with HCM, but not in controls, 2) There is evident segregation with HCM on the 8 families described, and 3) It is located in an active site of the protein where a variant in the same amino acid has already been clearly established as pathogenic (p.Arg652Gly). Interestingly, the exclusive presence of the variant in our region could correspond to a founder effect in the Balearic Islands, Spain, which we have further investigated. IBD/coalescent-based allele dating analysis reveals that the origin of this allele is 96 generations away which would correspond to 1900–2400 years ago, when the Balearic Islands were already populated. Conclusions We can define the p.Arg652Lys variant in MYH7 as LP in HCM and a founder effect is in the Balearic Islands is highly probable due to the exclusive presence at the region and the dating analysis of it. Funding Acknowledgement Type of funding sources: None.

Advanced microstructural substrate detection in pre-hypertrophic HCM and its relationship to arrhythmogenesis; a hybrid CMR-ECG-Imaging study

Abstract Background Hypertrophic cardiomyopathy is defined in three domains; clinically by unexplained hypertrophy, genetically by sarcomeric gene mutations and histologically by disarray, small vessel disease and fibrosis. Both ischaemia and myocyte disarray have been implicated in arrhythmogenesis and sudden cardiac death but whether disarray occurs before hypertrophy and its relationship to ischaemia is unknown. Diffusion-tensor CMR, perfusion mapping & ECG Imaging (ECGI) can measure disarray, ischaemia and electrical aberrance respectively in vivo. We aimed to investigate these in genotype positive (G+) subjects without hypertrophy (LVH−) to identify further subclinical manifestations of gene expression and whether these relate to ventricular arrhythmia formation. Methods Diffusion-tensor CMR (3-Tesla) using a motion-compensated spin-echo sequence was acquired in 3 short-axis slices. Quantitative adenosine stress perfusion mapping was performed using standard clinical protocols. A novel ECGI vest, containing 256 unipolar electrodes acquired a 5-minute recording of body-surface potentials to quantify conduction and repolarisation dynamics intervals. Results ECGI/CMR was performed on 68 mutation carriers from 64 families and 24 age sex and ethnicity matched healthy controls. Of the mutation carriers, median age was 33 (24–41 years), 57% (39) were female, and 79% (54) were white. Mutations were 39 (57%) MYBPC3, 19 (28%) MYH7, 1 (1%) MYL2 and 9 (12%) were thin filament/non-sarcomeric mutations. There was no significant difference in ejection fraction or LV mass, however G+LVH− had a higher maximum wall thickness (9 (9–10) vs 8 (7–9) mm p=0.003). Compared to healthy volunteers, G+LVH− individuals had more perfusion defects (18/64 (30%) vs 0, p=0.004), lower Fractional Anisotropy (FA) (suggestive of more disarray) (0.32±0.02 vs 0.34±0.02, p<0.0001) and more prolonged Activation–Recovery Intervals (ARI, a surrogate for action potential duration (259±40 vs 240±31 ms, p=0.03). In G+LVH−, patients with perfusion defects had more prolonged ARI (263 (248 vs 292) vs 246 (225–283) ms, p=0.03) and lower FA suggestive of more disarray (0.32±0.2 vs 0.31±0.1, p=0.04). Conclusion Ischaemia, myocyte disarray and electrical abnormalities occur even in the absence of hypertrophy in HCM. These abnormalities associate to form a complex a clinical phenotype. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): British Heart FoundationBarts Charity

Cardiac resynchronization therapy: association between genetically determinated dilated cardiomyopathy and dissinchronopathy

Abstract Background Patients with non-ischemic dilated cardiomyopathy (DCM) and left bundle branch block (LBBB) often undergoes cardiac resynchronization therapy (CRT). Despite CRT only a small group of patients restore normal left ventricular geometry and function. Many predictors of response to CRT have been described, but there are still insufficient data on the role of genetic mutations in sarcomere, cytoskeletal or desmosomal genes. Purpose To asses the role of genetic background as predictor of response after CRT in patient DCM and LBBB. Methods We retrospectively analyzed DCM patients with successful CRT implantation and available genetic testing consecutively included in the CRT-Registry of our Institution. DCM was defined by the presence of left ventricular or biventricular dilatation and systolic dysfunction in the absence of abnormal loading conditions or coronary artery disease sufficient to cause global systolic impairment. Changes in main echocardiographic parameters: left ventricular ejection fraction (LVEF), LV End Systolic and End Diastolic Volume (LVESV and LVEDV), where compared between basal and 24–48 months of follow up. LV remodeling was defined by relative changes (Δ) in LV End Systolic Volume (LVESV) [(follow-up LVESV − PRE LVESV) / PRE LVESV × 100)]. Patients were considered super-responders (SR) if LVEF at 24–48 months was>50%. Genetic testing was done by Next Generation DNA and all variants were validated with bidirectional Sanger sequencing. Variants of uncertain significance (VUS) were excluded from the analysis. Patients being carrier of pathogenic (P) or likely pathogenic (LP) variants were considered affected by genetic DCM (GEN+ DCM). Patients non carrier of P/LP variants and with no evidence of familial disease were considered affected by non-genetically determined DCM (GEN− DCM). Results 73 patients met the inclusion criteria, 23 patients were GEN+ DCM, the remaining 50 patients had negative genetic test and no family history of DCM. Baseline characteristics were similar between groups. GEN− group was characterized by a greater improvement in LVEF (39±12 vs 29±12, p=0,006) and a greater relative reduction in LVESV (ΔLVESV 43% vs 18%, p=0,007). GEN− patients had a 33 ml higher mean LVESV reduction at 24–48 months after CRT, indipendently of their respective baseline values. 20 patients (27% of the total population) suffered of heart failure related death, heart transplantation or left ventricular assistance device implantation during follow up and the prevalence was significantly higher in GEN+ group (43% vs 20%, p=0,037). Coherently, patients in the GEN+ group showed a lower prevalence of super responders (4%, vs 24%, p=0,02) after CRT. Conclusions Non-genetically determined DCM DCM is associated with a better clinical and instrumental response to CRT and a higher probability of being super responders. Furthermore, our data support the hypothesis about dyssyncronopathy as a specific clinical entity inside DCM diseases. Funding Acknowledgement Type of funding sources: None.

Promise or peril: the ECG in HCM

Abstract Introduction Hypertrophic cardiomyopathy is a complex disease of the myocardium characterised by left ventricular hypertrophy >15mm in any one segment, in the absence of loading conditions. The phenotypic variability and inhomogeneous nature of the condition have resulted in difficulties with diagnosis. Despite the significant progression in cardiac imaging and genetics, the electrocardiogram (ECG) remains the cornerstone of initial evaluation of patients with HCM and in the screening of families. Moreover, the ECG is in widespread use for pre-participation sports screening. Purpose Original and contemporary studies indicate that the ECG is normal in only 6–10% of patients with echocardiographic evidence of HCM. We hypothesised that the ECG may be normal in a significant proportion of HCM patients. This study sought to reassess the ECG as a screening tool in a HCM cohort. Methods 112 patients were selected randomly from the database of a specialist cardiomyopathy clinic. Their most recent ECG, clinical and imaging data were reviewed. All patients had echocardiographic HCM and were carriers of pathogenic sarcomere gene mutations. Patients with phenocopies were excluded. ECG data for 100 age and sex-matched controls was also analysed. ECG interpretation was performed using international criteria. Results 18% of patients with a clinical diagnosis of HCM by conventional diagnostic standards (LV wall thickness >15mm) had a normal ECG. A further 7% had a normal ECG with a mild HCM phenotype (LV wall thickness of 13–14mm). The most common abnormality observed was T wave inversion (TWI) in 28%. An additional unexpected finding in the HCM group was isolated TWI in lead aVL. This occurred in 27% of patients in the absence of any other repolarisation abnormalities, compared with 1% of controls. The significance of this finding is unclear. 27% of HCM patients displayed voltage criteria for left ventricular hypertrophy by either Cornell or Sokolow-Lyon criteria, with just 4% meeting criteria for both. 13% of HCM patients had corrected QT prolongation, in the absence of medications responsible for this. Conclusion The ECG continues to play a pivotal role in HCM diagnosis but its sensitivity to detect disease has been over-estimated. Up to a quarter of patients with HCM have a normal ECG. This is significantly higher than previously reported. The ECG in isolation therefore is not a reliable tool for screening for HCM in the general population and especially unreliable in at-risk subjects. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): The Mater Foundation

Atomic force microscopy identifies the alteration of rheological properties of the cardiac fibroblasts in idiopathic restrictive cardiomyopathy.

Restrictive cardiomyopathy (RCM) is a rare disease characterized by increased ventricular stiffness and preserved ventricular contraction. Various sarcomere gene variants are known to cause RCM; however, more than a half of patients do not harbor such pathogenic variants. We recently demonstrated that cardiac fibroblasts (CFs) play important roles in inhibiting the diastolic function of cardiomyocytes via humoral factors and direct cell–cell contact regardless of sarcomere gene mutations. However, the mechanical properties of CFs that are crucial for intercellular communication and the cardiomyocyte microenvironment remain less understood. In this study, we evaluated the rheological properties of CFs derived from pediatric patients with RCM and healthy control CFs via atomic force microscopy. Then, we estimated the cellular modulus scale factor related to the cell stiffness, fluidity, and Newtonian viscosity of single cells based on the single power-law rheology model and analyzed the comprehensive gene expression profiles via RNA-sequencing. RCM-derived CFs showed significantly higher stiffness and viscosity and lower fluidity compared to healthy control CFs. Furthermore, RNA-sequencing revealed that the signaling pathways associated with cytoskeleton elements were affected in RCM CFs; specifically, cytoskeletal actin-associated genes (ACTN1, ACTA2, and PALLD) were highly expressed in RCM CFs, whereas several tubulin genes (TUBB3, TUBB, TUBA1C, and TUBA1B) were down-regulated. These results implies that the signaling pathways associated with cytoskeletal elements alter the rheological properties of RCM CFs, particularly those related to CF–cardiomyocyte interactions, thereby leading to diastolic cardiac dysfunction in RCM.

Abstract P2052: Lowered Pro-fibrotic And Damage Associated Molecular Pattern Gene Expressions After Exercise Training In A Mouse Model Of Hypertrophic Cardiomyopathy

Background: Hypertrophic cardiomyopathy (HCM) is the most frequent inherited cardiac disease, most often caused by mutations in sarcomere genes. The disease is characterized by left ventricular (LV) hypertrophy, increased risk of arrhythmias and diastolic dysfunction, due to cardiomyocyte hypercontractility, myocyte disarray and fibrosis. Fibrosis is a marker of worse prognosis, adverse remodeling and an increased risk of sudden cardiac death. Hypothesis: We hypothesized that exercise training could attenuate fibrosis development in mice genetically predisposed to HCM. Methods: We allocated male α-Myh6 R403Q/+ to high intensity interval treadmill running or sedentary behavior (N=11 per group) for a total of 6 weeks. HCM was induced in all mice by cyclosporine A given via the feed for the last 3 of the 6 week exercise protocol. All mice underwent echocardiography and an exercise test at weeks 0, 3, and 6, before harvesting LVs for digital droplet PCR (ddPCR) and a qPCR immune array. Results: Exercise training lead to a 2-fold increase in exercise capacity as measured by total distance ran during exercise testing (p<0.0001). In exercised HCM mice, several key fibrosis-related genes were lowered compared to sedentary HCM mice as measured by ddPCR (N=11 per group): Collagen 1 by 51 % (p=0.03), collagen 3 by 54 % (p=0.02), fibronectin by 51 % (p=0.01) and lysyl oxidase by 42 % (p=0.05). An array of 87 selected immune-related genes showed that 39 genes were upregulated >1.5 fold in sedentary HCM mice compared to sedentary wild type controls (N=3 samples, pooled). Twelve upregulated genes belonged to damage associated-molecular patterns (DAMPs). Several of the DAMP genes were lower in exercised HCM mice compared to sedentary HCM mice (N=10-11 per group): Biglycan was lowered by 29 %, versican by 22 % and fibronectin by 55 %. Trends were also found for lowered expression of syndecan 1 (by 26 %), fibromodulin (by 55 %), and tenacin C (by 49 %) (0.07<p<0.08). There was no difference in maximal wall thickness or function measured by echocardiography. Conclusion: Exercise training led to a lower expression of key fibrosis-related genes in an inducible mouse model of HCM. Initial results indicate that attenuation of DAMP signaling might be involved in the mechanism for this effect.

Comparative analysis of right ventricular strain in Fabry cardiomyopathy and sarcomeric hypertrophic cardiomyopathy.

To perform a comparative analysis of right ventricle (RV) myocardial mechanics, assessed by 2D speckle-tracking echocardiography (2D-STE), between patients with Fabry disease and patients with sarcomeric disease. Patients with Fabry cardiomyopathy (FC) (n = 28) were compared with patients with sarcomeric hypertrophic cardiomyopathy (HCM), matched for degree of left ventricle hypertrophy (LVH) and demographic characteristics (n = 112). In addition, patients with Fabry disease and no LVH [phenotype-negative carriers of pathogenic α-galactosidase gene mutations (GLA LVH-)] (n = 28) were compared with age and sex-matched carriers of sarcomeric gene mutations without LVH [Phenotype-negative carriers of pathogenic sarcomeric gene mutations (Sarc LVH-)] (n = 56). Standard echocardiography and 2D-STE were performed in all participants. Despite a subtle impairment of RV global longitudinal strain (RV-GLS) was common in both groups, patients with FC showed a more prominent reduction of RV free wall longitudinal strain (RV-FWS) and lower values of difference between RV-FWS and RV-GLS (ΔRV strain), in comparison to individuals with HCM (P < 0.001 and P = 0.002, respectively). RV-FWS and ΔRV strain demonstrated an independent and additive value in discriminating FC from HCM, over the presence of symmetric LVH, systolic anterior motion of the mitral valve and RV hypertrophy. Similar results were found in GLA LVH- patients: they had worse RV-FWS and lower values of ΔRV strain as compared to Sarc LVH- patients (both P < 0.001). Patients with FC show a specific pattern of RV myocardial mechanics, characterized by a larger impairment of RV-FWS and lower ΔRV strain in comparison to patients with HCM, which may be helpful in the differential diagnosis between these two diseases.

An integration-free iPSC line ZZUNEUi028-A derived from a patient with hypertrophic cardiomyopathy carrying a heterozygous mutation (c. 1504 C > T) in MYBPC3 gene

Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease often caused by sarcomeric gene mutations. MYBPC3 is one of the most common genes associated with HCM. In this study, we generated a human induced pluripotent stem cell line ZZUNEUi028-A from a 19-year-old male HCM patient with c. 1504C → T in MYBPC3 gene using non-integrative Sendai viral reprogramming technology. This cell line expresses pluripotency markers, exhibits a normal male karyotype (46, XY) and can differentiate into all three germ layers in vitro. ZZUNEUi028-A can serve as a cell disease model in the understanding of HCM pathogenesis.

Echocardiographic characteristics of PRKAG2 syndrome: a research using three-dimensional speckle tracking echocardiography compared with sarcomeric hypertrophic cardiomyopathy

BackgroundPRKAG2 syndrome is a rare disease characterized as left ventricular hypertrophy (LVH), ventricular preexcitation syndrome, and sudden cardiac death. Its natural course, treatment, and prognosis were significantly different from sarcomeric hypertrophic cardiomyopathy (HCM). However, it is often clinically misdiagnosed as sarcomeric HCM. PRKAG2 patients tend to experience delayed treatment. The delay may lead to adverse outcomes. This study aimed to identify the echocardiographic parameters which can differentiate PRKAG2 syndrome from sarcomeric HCM.MethodsNine PRKAG2 patients with LVH, 41 HCM patients with sarcomere gene mutations, and 202 healthy volunteers were enrolled. Clinical characteristics, conventional echocardiography, and three-dimensional images were recorded, and reviewed by an attending cardiologist. We evaluated the parameters of left ventricular strains from three-dimensional speckle tracking echocardiography (3D STE) by TomTec software. Receiver operating characteristic (ROC) curves analysis was used to assess clinical and echocardiographic parameters’ differential diagnosis potential.ResultsThe heart rate (HR) of the PRKAG2 group was significantly lower than both the healthy group (53.11 ± 10.14 vs. 69.22 ± 10.48 bpm, P < 0.001) and the sarcomeric HCM group (53.11 ± 10.14 vs. 67.23 ± 10.32 bpm, P = 0.001). The PRKAG2 group had similar interventricular septal thickness (IVS), posterior wall thickness (PWT), and maximum wall thickness (MWT) to the HCM group (P > 0.05). The absolute value of GLS in the PRKAG2 group was significantly higher than HCM patients (-18.92 ± 4.98 vs. -13.43 ± 4.30%, P = 0.004). SV calculated from EDV and ESV in PRKAG2 syndrome showed a higher value than sarcomeric HCM (61.83 ± 13.52 vs. 44.96 ± 17.53%, P = 0.020). The area under the ROC curve (AUC) for HR + GLS was 0.911 (0.803 -1). For HR + GLS, the sensitivity and specificity of the best cut-off value (0.114) were 69.0% and 100%, respectively.ConclusionsPRKAG2 patients present deteriorated LV diastolic function and preserved LV systolic function. Bradycardia and preserved GLS are useful to identify PRKAG2 syndrome from sarcomeric HCM, which may be beneficial for clinical decision-making.

The Genetic Architecture of Hypertrophic Cardiomyopathy in Hungary: Analysis of 242 Patients with a Panel of 98 Genes.

Hypertrophic cardiomyopathy (HCM) is a primary disease of the myocardium most commonly caused by mutations in sarcomeric genes. We aimed to perform a nationwide large-scale genetic analysis of a previously unreported, representative HCM cohort in Hungary. A total of 242 consecutive HCM index patients (127 men, 44 ± 11 years) were studied with next generation sequencing using a custom-designed gene-panel comprising 98 cardiomyopathy-related genes. A total of 90 patients (37%) carried pathogenic/likely pathogenic (P/LP) variants. The percentage of patients with P/LP variants in genes with definitive evidence for HCM association was 93%. Most of the patients with P/LP variants had mutations in MYBPC3 (55 pts, 61%) and in MYH7 (21 pts, 23%). Double P/LP variants were present in four patients (1.7%). P/LP variants in other genes could be detected in ≤3% of patients. Of the patients without P/LP variants, 46 patients (19%) carried a variant of unknown significance. Non-HCM P/LP variants were identified in six patients (2.5%), with two in RAF1 (p.Leu633Val, p.Ser257Leu) and one in DES (p.Arg406Trp), FHL1 (p.Glu96Ter), TTN (p.Lys23480fs), and in the mitochondrial genome (m.3243A>G). Frameshift, nonsense, and splice-variants made up 82% of all P/LP MYBPC3 variants. In all the other genes, missense mutations were the dominant form of variants. The MYBPC3 p.Gln1233Ter, the MYBPC3 p.Pro955ArgfsTer95, and the MYBPC3 p.Ser593ProfsTer11 variants were identified in 12, 7, and 13 patients, respectively. These three variants made up 36% of all patients with identified P/LP variants, raising the possibility of a possible founder effect for these mutations. Similar to other HCM populations, the MYBPC3 and the MYH7 genes seemed to be the most frequently affected genes in Hungarian HCM patients. The high prevalence of three MYBPC3 mutations raises the possibility of a founder effect in our HCM cohort.

Single-cell transcriptomics provides insights into hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a genetic heart disease that is characterized by unexplained segmental hypertrophy that is usually most pronounced in the septum. While sarcomeric gene mutations are often the genetic basis for HCM, the mechanistic origin for the heterogeneous remodeling remains largely unknown. A better understanding of the gene networks driving the cardiomyocyte (CM) hypertrophy is required to improve therapeutic strategies. Patients suffering from HCM often receive a septal myectomy surgery to relieve outflow tract obstruction due to hypertrophy. Using single-cell RNA sequencing (scRNA-seq) on septal myectomy samples from patients with HCM, we identify functional links between genes, transcription factors, and cell size relevant for HCM. The data show the utility of using scRNA-seq on the human hypertrophic heart, highlight CM heterogeneity, and provide a wealth of insights into molecular events involved in HCM that can eventually contribute to the development of enhanced therapies.

Sarcomeric gene mutations in phenotypic positive hypertrophic cardiomyopathic patients in Indian population.

HCM is a monogenic cardiac disorder with a high risk of sudden cardiac death, heterogeneous phenotypic expression and genetic profile. HCM is expressed as autosomal dominant in fashion with the prevalence of 1:500 in the general population. The main objective of the current study was to unravel the mutation status in sarcomeric genes in urbanizing Pune population. HCM patients were recruited from Bharti hospital and Poona hospital and research centre, Pune after being screened by 2-D echocardiography. DNA was extracted from whole blood samples and PCR amplification was performed for selected exons from pre-selected genes, amplimers of >300 b.p were restriction digested and the SSCP technique was optimized for maximum result output. HCM patients shows the maximum prevalence of mitral regurgitation (23.3%) while the minimum prevalence was left auricular diameter (10%). Maximum variation spectrum was present in MYBPC3 genes as most of them were "benign" type as per Polyphen-2 tool status. Mutations in the MYH7 gene produce a prominent impact on splicing by the creation of a new SRP40 binding site (Exon Splicing Enhancer) as predicted by Human Splicing Finder 3.1. I736T mutation in the MYH7 gene results in replacement of β-strand by α-helix upstream from mutation site which may have a profound impact on protein tertiary structure as predicted by Polyphen-2 tool (probably damaging-1.00). Also, two 'novel' mutations and one 'novel' variation were reported in the present study. Thus, the MYBPC3 gene shows maximum mutation load among other sarcomeric genes. Double gene mutations do not represent much severe pathophysiology as compared to single gene mutated and genotypic negative HCM patients.

Genotype-Phenotype Correlation in Hypertrophic Cardiomyopathy: New Variant p.Arg652Lys in MYH7.

Hypertrophic cardiomyopathy (HCM) is a genetic disease characterised by increased left ventricle (LV) wall thickness caused by mutations in sarcomeric genes. Finding a causal mutation can help to better assess the proband’s risk, as it allows the presence of the mutation to be evaluated in relatives and the follow-up to be focused on carriers. We performed an observational study of patients with HCM due to the novel p.Arg652Lys variant in the MYH7 gene. Eight families and 59 patients are described in the follow-up for a median of 63 months, among whom 39 (66%) carry the variant. Twenty-five (64%) of carriers developed HCM. A median maximum LV wall thickness of 16.5 mm was described. The LV hypertrophy was asymmetric septal in 75% of cases, with LV outflow tract obstruction in 28%. The incidence of a composite of serious adverse cardiovascular events (sudden death, aborted sudden death, appropriate implantable cardiac defibrillator discharge, an embolic event, or admission for heart failure) was observed in five (20%) patients. Given the finding of the p.Arg652Lys variant in patients with HCM, but not in controls, with evident segregation in patients with HCM from eight families and the location in an active site of the protein, we can define this variant as likely pathogenic and associated with the development of HCM.

English

BACKGROUND Peripartum cardiomyopathy is a rare, dilated cardiomyopathy with systolic dysfunction that occurs in the late pregnancy or more commonly in the early postpartum period. Risk factors include pre-eclampsia, advanced maternal age, multiple gestation. Although the complete pathogenesis is unclear, researches over the past few years suggest the importance of vasculo-hormonal pathways in women with underlying susceptibility and sarcomere gene mutation. Most of the patients will recover with adequate systolic function, although very few may go on to chronic cardiomyopathy. Other potential complications include thromboembolism and arrhythmias. METHODS This is a prospective study conducted at Kanyakumari Government Medical College between May 2019 and May 2021. 10 cases were observed and followed up. ANC cases with acute heart failure and no history of previous heart diseases were included in the study. Patients with known heart diseases were excluded from the study. RESULTS 10 cases of ANC cases were diagnosed with peripartum cardiomyopathy with half of them having comorbidity and others were comorbid free. Diagnosis was confirmed with echocardiography and all the patients recovered with medical management. CONCLUSIONS Though peripartum cardiomyopathy is a rare occurring event, incidence of 10 cases in a period of 2 years highlights the need for us to be aware of this peripartum cardiac event and have it as a differential diagnosis in the situational setting at the back of the mind. Since this is a serious medical condition that affects pregnant women, prompt and timely medical intervention will save the patient from serious life-threatening complications. KEY WORDS Peripartum Cardiomyopathy, Pregnancy, Heart Disease, Dyspnoea in Pregnancy.

Mavacamten: A First-in-class Oral Modulator of Cardiac Myosin for the Treatment of Symptomatic Hypertrophic Obstructive Cardiomyopathy.

Hypertrophic cardiomyopathy is the most common monogenic cardiovascular disease that is caused by sarcomeric protein gene mutations. A hallmark of the most common form of the disease is outflow obstruction secondary to systolic narrowing of the left ventricular outflow tract from septal hypertrophy, mitral valve abnormalities and, most importantly, hyperdynamic contractility. Recent mechanistic studies have identified excessive myosin adenosine triphosphatase activation and actin-myosin cross-bridging as major underlying causes. These studies have led to the development of mavacamten, a first-in-class myosin adenosine triphosphatase inhibitor and the first specific therapy for hypertrophic obstructive cardiomyopathy. Preclinical and subsequent pivotal clinical studies have demonstrated the efficacy and safety of mavacamten. A remarkable improvement among treated patients in peak oxygen consumption, functional capacity, symptom relief and post-exercise left ventricular outflow tract gradient, along with dramatic reductions in heart failure biomarkers, suggests that this new medication will be transformative for the symptom management of hypertrophic obstructive cardiomyopathy. There is also hope and early evidence that mavacamten may delay or obviate the need for invasive septal reduction therapies. In this article, we review the current evidence for the efficacy and safety of mavacamten and highlight important considerations for its clinical use.

MiRNA-Regulated Pathways for Hypertrophic Cardiomyopathy: Network-Based Approach to Insight into Pathogenesis.

Hypertrophic cardiomyopathy (HCM) is the most common hereditary heart disease. The wide spread of high-throughput sequencing casts doubt on its monogenic nature, suggesting the presence of mechanisms of HCM development independent from mutations in sarcomeric genes. From this point of view, HCM may arise from the interactions of several HCM-associated genes, and from disturbance of regulation of their expression. We developed a bioinformatic workflow to study the involvement of signaling pathways in HCM development through analyzing data on human heart-specific gene expression, miRNA-target gene interactions, and protein–protein interactions, available in open databases. Genes regulated by a pool of miRNAs contributing to human cardiac hypertrophy, namely hsa-miR-1-3p, hsa-miR-19b-3p, hsa-miR-21-5p, hsa-miR-29a-3p, hsa-miR-93-5p, hsa-miR-133a-3p, hsa-miR-155-5p, hsa-miR-199a-3p, hsa-miR-221-3p, hsa-miR-222-3p, hsa-miR-451a, and hsa-miR-497-5p, were considered. As a result, we pinpointed a module of TGFβ-mediated SMAD signaling pathways, enriched by targets of the selected miRNAs, that may contribute to the cardiac remodeling in HCM. We suggest that the developed network-based approach could be useful in providing a more accurate glimpse on pathological processes in the disease pathogenesis.

Abstract 11879: The Genetic Characteristics Based on Next Generation Sequencing in Patients With Hypertrophic Cardiomyopathy

Objective: This study aimed to explore the genetic epidemiological characteristics in patients with hypertrophic cardiomyopathy (HCM). Methods: We prospectively enrolled 383 unrelated HCM probands who received genetic testing and 3.0 T cardiac MRI examination, including 118 familial HCM and 265 sporadic HCM. The diagnosis of HCM is based on the diagnostic criteria of the American Heart Association and American College of Cardiology guidelines. Patients with familial HCM underwent targeted next generation sequencing including 117 candidate pathogenic genes associated with cardiomyopathies, while sporadic HCM underwent whole-exome sequencing. The genotypic characteristics were analyzed. Results: Among the 383 unrelated Chinese HCM probands, we reported 56 new pathogenic or likely pathogenic gene site mutations, including 3 new rare non-sarcomeric gene mutations and 53 new sarcomeric gene mutations. According to the analysis of genotypic characteristics, it was found that the frequency of rare genes was 3.4%, and the positive rate of sarcomere protein gene detection was 62.4%. Among them, MYH7 and MYBPC3 are the most common pathogenic genes, accounting for 61.9% of sarcomere protein gene mutations. Additionally, in the included HCM population, there was no significant difference in the positive detection rate of sarcomere protein gene between familial HCM and sporadic HCM (66.1% vs 64%, P = 0.7). The proportion of sporadic HCM carrying polygenic mutations was higher than that of familial HCM (11.2% vs. 1.8%, P = 0.003). Conclusion: We reported 56 new gene mutations, which expanded the gene spectrum of HCM. Additionally, the frequency of rare disease genes in the HCM cohort is 3.4%, and the composition ratio of sarcomere protein gene is similar to that of North American or European HCM populations. However, the gene positive rate of sporadic HCM is similar to that of familial HCM, but the composition ratio of genotypes is different.