Myocardium In Hypertrophic Cardiomyopathy Research Articles

Integrative analysis of transcriptome, DNA methylome and chromatin accessibility reveals candidate therapeutic targets in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease and is characterized by primary left ventricular hypertrophy usually caused by mutations in sarcomere genes. The mechanism underlying cardiac remodeling in HCM remains incompletely understood. An investigation of HCM through integrative analysis at multi-omics levels will be helpful for treating HCM. DNA methylation and chromatin accessibility, as well as gene expression, were assessed by nucleosome occupancy and methylome sequencing (NOMe-seq) and RNA-seq, respectively, using the cardiac tissues of HCM patients. Compared with those of the controls, the transcriptome, DNA methylome and chromatin accessibility of the HCM myocardium showed multifaceted differences. At the transcriptome level, HCM hearts returned to the fetal gene program through decreased sarcomeric and metabolic gene expression and increased extracellular matrix gene expression. In the DNA methylome, hypermethylated and hypomethylated differentially methylated regions (DMRs) were identified in HCM. At the chromatin accessibility level, HCM hearts showed changes in different genome elements. Several transcription factors (TFs), including SP1 and EGR1, exhibited a fetal-like pattern of binding motifs in nucleosome-depleted regions (NDRs) in HCM. In particular, the inhibition of SP1 or EGR1 in an HCM mouse model harboring sarcomere mutations markedly alleviated the HCM phenotype of the mutant mice and reversed fetal gene reprogramming. Overall, this study not only provides a high precision multi-omics map of HCM heart tissue but also sheds light on the therapeutic strategy by intervening the fetal gene reprogramming in HCM.

Effects of ranolazine on the arrhythmic substrate in hypertrophic cardiomyopathy.

Introduction: Hypertrophic cardiomyopathy (HCM) is a leading cause of lethal arrhythmias in the young. Although the arrhythmic substrate has been hypothesised to be amenable to late Na+ block with ranolazine, the specific mechanisms are not fully understood. Therefore, this study aimed to investigate the substrate mechanisms of safety and antiarrhythmic efficacy of ranolazine in HCM. Methods: Computational models of human tissue and ventricles were used to simulate the electrophysiological behaviour of diseased HCM myocardium for variable degrees of repolarisation impairment, validated against in vitro and clinical recordings. S1-S2 pacing protocols were used to quantify arrhythmic risk in scenarios of (i) untreated HCM-remodelled myocardium and (ii) myocardium treated with 3µM, 6µM and 10µM ranolazine, for variable repolarisation heterogeneity sizes and pacing rates. ECGs were derived from biventricular simulations to identify ECG biomarkers linked to antiarrhythmic effects. Results: 10µM ranolazine given to models manifesting ventricular tachycardia (VT) at baseline led to a 40% reduction in number of VT episodes on pooled analysis of >40,000 re-entry inducibility simulations. Antiarrhythmic efficacy and safety were dependent on the degree of repolarisation impairment, with optimal benefit in models with maximum JTc interval <370ms. Ranolazine increased risk of VT only in models with severe-extreme repolarisation impairment. Conclusion: Ranolazine efficacy and safety may be critically dependent upon the degree of repolarisation impairment in HCM. For moderate repolarisation impairment, reductions in refractoriness heterogeneity by ranolazine may prevent conduction blocks and re-entry. With severe-extreme disease substrates, reductions of the refractory period can increase re-entry sustainability.

Abstract 12080: Comprehensive Proteomics Profiling of Human Myocardium Reveals Signaling Pathways Dysregulated in Severe Forms of Hypertrophic Cardiomyopathy

Introduction: Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular disease, affecting 1 in 200-500 people. There is significant heterogeneity in disease severity. The signaling pathways that link gene mutations to severe HCM disease remain unknown. Analysis of the myocardial proteome is a novel approach to understanding severe forms of HCM. Hypothesis: Comprehensive proteomics profiling of myocardium identifies signaling pathways that are differentially regulated in severe forms of HCM. Methods: Proteomics profiling of 7289 proteins from myocardium was performed on patients with HCM. Univariable analysis with the Wilcoxon rank sum test or Spearman’s rank correlation test was used to determine the association between protein concentration and 5 clinical indicators of severe HCM: 1) left ventricular ejection fraction (LVEF), 2) atrial fibrillation (AF), 3) ventricular arrhythmias, 4) maximum septal thickness, and 5) late gadolinium enhancement (LGE) by cardiac magnetic resonance (CMR). Pathway analysis of proteins with significantly different concentrations (i.e., nominal p&lt;0.05) in association with each clinical indicator was executed. Results: There were 106 patients with HCM included in the study. Pathway analysis of proteins associated with each indicator of severe HCM revealed dysregulation of inflammatory pathways and Ras-MAPK-related pathways ( Figure ). Metabolic pathways and adhesion pathways were dysregulated in association with LVEF and AF. Dysregulation of angiogenesis pathways (e.g., HIF-1, VEGF) was associated with LGE (FDR&lt;0.05). Conclusions: Comprehensive proteomics profiling of human HCM myocardium was used to identify dysregulated signaling pathways associated with clinical features of severe HCM. Findings from this study support the role of both known (e.g., inflammation, metabolism, adhesion, and angiogenesis) and novel (e.g., Ras-MAPK) pathways in the development of severe forms of HCM.

DNA methylome and transcriptome profiling reveal key electrophysiology and immune dysregulation in hypertrophic cardiomyopathy

ABSTRACT Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease. However, a detailed DNA methylation (DNAme) landscape has not yet been elucidated. Our study combined DNAme and transcriptome profiles for HCM myocardium and identify aberrant DNAme associated with altered myocardial function in HCM. The transcription of methylation-related genes did not significantly differ between HCM and normal myocardium. Nevertheless, the former had an altered DNAme profile compared with the latter. The hypermethylated and hypomethylated sites in HCM tissues had chromosomal distributions and functional enrichment of correlated genes differing from those of their normal tissue counterparts. The GO analysis of network underlying the genes correlated with DNAme alteration and differentially expressed genes (DEGs) shows functional clusters centred on immune cell function and muscle system processes. In KEGG analysis, only the calcium signalling pathway was enriched either by the genes correlated with changes in DNAme or DEGs. The protein-protein interactions (PPI) underlying the genes altered at both the DNAme and transcriptional highlighted two important functional clusters. One of these was related to the immune response and had the estrogen receptor-encoding ESR1 gene as its node. The other cluster comprised cardiac electrophysiology-related genes. Intelliectin-1 (ITLN1), a component of the innate immune system, was transcriptionally downregulated in HCM and had a hypermethylated site within 1500 bp upstream of the ITLN1 transcription start site. Estimates of immune infiltration demonstrated a relative decline in immune cell population diversity in HCM. A combination of DNAme and transcriptome profiles may help identify and develop new therapeutic targets for HCM.

Feline myocardial transcriptome in health and in hypertrophic cardiomyopathy-A translational animal model for human disease.

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats, characterized by primary left ventricular hypertrophy. Feline HCM closely resembles human HCM and is suggested as translational animal model for the human disease. A genetic cause is established in humans and suspected for cats, but little is known about the gene expression and pathways involved in the pathogenesis of HCM. To investigate the myocardial transcriptome changes in HCM, RNA sequencing was conducted on left ventricle (LV) and left atrium (LA) samples of healthy cats and cats with HCM (each n = 5; 20 samples). Ingenuity Pathway Analysis was used to determine functional pathways, regulators, and networks. Distinct gene expression profiles were identified in the LV and LA of the feline healthy and HCM myocardium. Analysis of differentially expressed mRNAs (>2 fold; FDR < 0.01) found chamber-specific (LV vs. LA) expression in both healthy and HCM groups, with higher transcriptional activity in the LA. Genes that contribute to the distinct structure and function of each chamber in health and HCM were identified in the regional comparison. The gene expression profiles of HCM compared to healthy hearts revealed disease related genes, including THBS4 and KLHL33 (LV), FAM177B and THRSP (LA), the latter 3 have not been reported for the myocardium so far, as the top differently expressed genes in the HCM heart. Differently expressed genes and functional pathways found in the HCM heart are associated with cardiac remodeling and fibrosis, inflammation, microvascular changes, calcium signaling and cardiac metabolism, with some regional differences. RhoGDI-RhoGTPase signaling, integrin and ILK signaling pathways, the LXR/RXR pathway in the LA, and the PPARα/RXRα, HIF1α and CXCR4 pathways in the LV might be of particular importance in the HCM disease process. This study identified region-specific myocardial gene transcription patterns as well as novel genes and pathways associated with HCM.

Increase in skeletal muscle extracellular volume as an under-recognised change detected at cardiac MRI in hypertrophic cardiomyopathy

To explore skeletal muscle change and its correlation with the myocardium in hypertrophic cardiomyopathy (HCM) using cardiac magnetic resonance imaging (cMRI) with T1 mapping and late gadolinium enhancement (LGE). This retrospective study enrolled 50 HCM patients and 35 healthy controls. The extracellular volume (ECV) of the skeletal muscle and myocardium, the presence and absence of LGE of the myocardium, and cardiac troponin T (cTnT), were assessed. In the HCM group, the elevated ECVskeletal group was defined as ECVskeletal >2 standard deviations (SD) above the mean value of the controls. Statistical analyses included Student's t-test, the Mann-Whitney U-test, and linear regression. ECVskeletal in the HCM group was higher than in the control group (mean 13.0 versus 10.9%; p<0.001), with 20 (40%) HCM patients having elevated ECVskeletal (ECVskeletal ≥13.7%). In the HCM group, ECVskeletal had a positive linear correlation with global myocardial ECV (r=0.37, p=0.009). In addition, the elevated ECVskeletal group had a higher cTnT than the non-elevated group (log cTnT, mean 1.55 versus 1.16, p=0.045). Furthermore, segmental myocardial ECV in the elevated ECVskeletal group was higher than in the non-elevated group, despite the presence or absence of myocardial LGE (median 30.1 versus 27.2%; 26.5 versus 24.6%, both p<0.001) or hypertrophy (median 29.0 versus 26.0%; 26.8 versus 24.8%, both p<0.001). In the HCM patients, ECVskeletal was higher than in the healthy controls. Furthermore, some ECVskeletal changes had corresponding changes in the cTnT and myocardium.

Abstract 13844: Comprehensive Proteomics Profiling of Myocardium Identifies Dysregulated Signaling Pathways in Hypertrophic Cardiomyopathy

Background: Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular disease. The signaling pathways that link gene mutations to the manifestation of clinically-overt HCM remain unknown. Hypothesis: Comprehensive proteomics profiling of myocardium identifies signaling pathways that are differentially regulated in HCM. Methods: We conducted a multicenter case-control study. Cases were patients with HCM who underwent septal myectomy. Controls were donors without cardiac disease whose heart was excised but could not be transplanted due to size mismatch. We performed proteomics profiling of 7289 proteins from myocardium and excluded 1222 proteins significantly correlated with age. We performed a univariable analysis of the remaining 6067 proteins to determine the association between protein concentration and disease status using the Wilcoxon rank sum test. We executed pathway analysis of proteins significantly dysregulated (i.e., univariable p &lt;0.05) in cases with HCM compared to controls. Pathways with false discovery rate [FDR] &lt;0.01 were considered to be dysregulated. Results: There were 121 patients included in the study, with 106 HCM cases and 15 controls. Among the 6067 proteins analyzed, 986 were differentially regulated between HCM cases and controls. Pathway analysis of these proteins revealed dysregulation of the Ras-MAPK pathway (FDR &lt; 0.0001) and multiple metabolic pathways, mainly related to amino acid metabolism ( Figure ). Pathways that are known to be dysregulated in HCM, such as the TNF pathway and those related with inflammation, were also dysregulated. Conclusions: The present study represents the largest-scale (n &gt;100) and most comprehensive proteomics profiling (&gt;7000 proteins) of human HCM myocardium to date, elucidating dysregulation of both novel (e.g., Ras-MAPK, amino acid metabolism) and known (e.g., TNF, inflammation) pathways in patients with HCM.

RNA-seq profiling reveals different pathways between remodeled vessels and myocardium in hypertrophic cardiomyopathy.

Coronary microvascular dysfunction (CMD) is a key pathophysiological feature of hypertrophic cardiomyopathy (HCM), contributing to myocardial ischemia and representing a critical determinant of patients' adverse outcome. The molecular mechanisms underlying the morphological and functional changes of CMD are still unknown. Aim of this study was to obtain insights on the molecular pathways associated with microvessel remodeling in HCM. Interventricular septum myectomies from patients with obstructive HCM (n=20) and donors' hearts (CTRL, discarded for technical reasons, n=7) were collected. Remodeled intramyocardial arterioles and cardiomyocytes were microdissected by laser capture and next-generation sequencing was used to delineate the transcriptome profile. We identified 720 exclusive differentially expressed genes (DEGs) in cardiomyocytes and 1315 exclusive DEGs in remodeled arterioles of HCM. Performing gene ontology and pathway enrichment analyses, we identified selectively altered pathways between remodeled arterioles and cardiomyocytes in HCM patients and controls. We demonstrate the existence of distinctive pathways between remodeled arterioles and cardiomyocytes in HCM patients and controls at the transcriptome level.

Myosins and MyomiR Network in Patients with Obstructive Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy. The molecular mechanisms determining HCM phenotypes are incompletely understood. Myocardial biopsies were obtained from a group of patients with obstructive HCM (n = 23) selected for surgical myectomy and from 9 unused donor hearts (controls). A subset of tissue-abundant myectomy samples from HCM (n = 10) and controls (n = 6) was submitted to laser-capture microdissection to isolate cardiomyocytes. We investigated the relationship among clinical phenotype, cardiac myosin proteins (MyHC6, MyHC7, and MyHC7b) measured by optimized label-free mass spectrometry, the relative genes (MYH7, MYH7B and MYLC2), and the MyomiR network (myosin-encoded microRNA (miRs) and long-noncoding RNAs (Mhrt)) measured using RNA sequencing and RT-qPCR. MyHC6 was lower in HCM vs. controls, whilst MyHC7, MyHC7b, and MyLC2 were comparable. MYH7, MYH7B, and MYLC2 were higher in HCM whilst MYH6, miR-208a, miR-208b, miR-499 were comparable in HCM and controls. These results are compatible with defective transcription by active genes in HCM. Mhrt and two miR-499-target genes, SOX6 and PTBP3, were upregulated in HCM. The presence of HCM-associated mutations correlated with PTBP3 in myectomies and with SOX6 in cardiomyocytes. Additionally, iPSC-derived cardiomyocytes, transiently transfected with either miR-208a or miR-499, demonstrated a time-dependent relationship between MyomiRs and myosin genes. The transfection end-stage pattern was at least in part similar to findings in HCM myectomies. These data support uncoupling between myosin protein/genes and a modulatory role for the myosin/MyomiR network in the HCM myocardium, possibly contributing to phenotypic diversity and providing putative therapeutic targets.

Contraction and electrophysiological abnormalities in myofilament mutation-positive and mutation-negative human HCM myocardium

Myofilament mutation-positive and mutation-negative hypertrophic cardiomyopathy (HCM) patients show different prognosis and arrhythmic burden that are likely related to the different pathogenesis. For instance, post-translational activation of CaMKII pathway is a specific biomarker of myofilament mutation-positive HCM while depressed sarcoplasmic reticulum calcium uptake is present in both groups. However, the functional consequences of a mutation-driven pathogenesis is still not completely understood.

Ablation of the N terminus of cardiac essential light chain promotes the super-relaxed state of myosin and counteracts hypercontractility in hypertrophic cardiomyopathy mutant mice.

In this study, we focus on the molecular mechanisms associated with the A57G (Ala57-to-Gly57) mutation in myosin essential light chains (ELCs), found to cause hypertrophic cardiomyopathy (HCM) in humans and in mice. Specifically, we studied the effects of A57G on the super-relaxed (SRX) state of myosin that may contribute to the hypercontractile cross-bridge behavior and ultimately lead to pathological cardiac remodeling in transgenic Tg-A57G mice. The disease model was compared to Tg-WT mice, expressing the wild-type human ventricular ELC, and analyzed against Tg-Δ43 mice, expressing the N-terminally truncated ELC, whose hearts hypertrophy with time but do not show any abnormalities in cardiac morphology or function. Our data suggest a new role for the N terminus of cardiac ELC (N-ELC) in modulation of myosin cross-bridge function in the healthy as well as in HCM myocardium. The lack of N-ELC in Tg-Δ43 mice was found to significantly stabilize the SRX state of myosin and increase the number of myosin heads occupying a low-energy state. In agreement, Δ43 hearts showed significantly decreased ATP utilization and low actin-activated myosin ATPase compared with A57G and WT hearts. The hypercontractile activity of A57G-ELC cross-bridges was manifested by the inhibition of the SRX state, increased number of myosin heads available for interaction with actin, and higher ATPase activity. Fiber mechanics studies, echocardiography examination, and assessment of fibrosis confirmed the development of two distinct forms of cardiac remodeling in these two ELC mouse models, with pathological cardiac hypertrophy in Tg-A57G, and near physiologic cardiac growth in Tg-Δ43 animals.

MicroRNA-221 is a potential biomarker of myocardial hypertrophy and fibrosis in hypertrophic obstructive cardiomyopathy.

Aim: Circulating microRNA expression has become a biomarker of cardiovascular disease; however, the association of microRNA expression between circulation and myocardium in hypertrophic cardiomyopathy remains unclear. The present study aimed to find a circulating biomarker correlated not only to myocardial expression, but also to cardiac hypertrophy and fibrosis. Method: Forty-two cases of hypertrophic obstructive cardiomyopathy (HOCM) diagnosed by echocardiography and magnetic resonance were analysed for microRNA expression in plasma and myocardial tissue. Results: The results showed that myocardial miR-221 was significantly increased (z = −2.249, P = 0.024) and significantly correlated with collagen volume fraction (CVF) (r = 0.516, P < 0.001), late gadolinium enhancement (LGE) (r = 0.307, P = 0.048), and peripheral circulation (r = 0.434, P = 0.004). Moreover, circulating miR-221 expression was significantly correlated with CVF (r = 0.454, P = 0.002), LGE (r = 0.630, P = 0.004), maximum interventricular septal thickness (MIVST) of echocardiography (r = 0.318, P = 0.042), and MIVST of magnetic resonance (r = 0.342, P = 0.027). The area under the receiver operating characteristic curve of miR-221 was 0.764. Conclusions: Circulating miR-221 is consistent with that in myocardial tissue, and correlated with myocardial fibrosis and hypertrophy. It can be used as a biomarker for evaluating myocardial hypertrophy and fibrosis in HOCM.

Native T1 time and extracellular volume fraction in differentiation of normal myocardium from non-ischemic dilated and hypertrophic cardiomyopathy myocardium: A systematic review and meta-analysis

BackgroundBoth native T1 time and extracellular volume (ECV) fraction have been shown to be important measures for the detection of myocardial fibrosis. However, ECV determination requires the administration of an intravenous contrast agent, whereas native T1 mapping can be performed without a contrast agent. MethodsHere, we conducted a meta-analysis of myocardial native T1 data obtained for non-ischemic cardiomyopathy (NIC) patients and controls. A literature review included studies that applied T1 mapping using modified Look–Locker inversion recovery to measure myocardial fibrosis, and the results were validated by comparing datasets for dilated cardiomyopathy (DCM) or hypertrophic cardiomyopathy (HCM) patients and healthy controls (HCs). ResultsWe identified 16 eligible studies. Pooled mean differences (MDs) and 95% confidence intervals (CIs) were estimated as follows. Native T1 at 1.5-T, DCM vs. HC: MD = 45.26 (95% CI: 30.92–59.59); HCM vs. HC: MD = 47.09 (95% CI: 32.42–61.76). Native T1 at 3.0-T, DCM vs. HC: MD = 82.52 (95% CI: 47.60–117.44); HCM vs. HC: MD = 115.87 (95% CI: 50.71–181.04). ECV at 1.5-T, DCM vs. HC: MD = 4.26 (95% CI: 3.06–5.46); HCM vs. HC: MD = 1.49 (95% CI: −1.45–4.43). ECV at 3.0-T, DCM vs. HC: MD = 8.40 (95% CI: 2.94–13.86); HCM vs. HC: MD = 8.02 (95% CI: 5.45–1–0.59). ConclusionIn conclusion, native T1 values were significantly different between NIC patients and controls. Native T1 mapping may be a useful noninvasive method to detect diffuse myocardial fibrosis in NIC patients.

Myocardial morphology in hypertrophic cardiomyopathy: the current state of the problem

The objective. Based on the modern sources of scientific data to analyze the morphological features of the myocardium in hypertrophic cardiomyopathy. The paper presents a literature review on current views on the features of structural remodeling of the left ventricular myocardium in patients with hypertrophic cardiomyopathy, as well as the most common classifications of this pathology. The emphasis is made on the problem of the interrelation of myocardial disarray and fibrosis. The “small vessel disease” is an important pathogenetic link in the development of heart failure, which enhances the relation between disorder of myocardial histoarchitectonics and progressive cardiac ischemia in hypertrophic cardiomyopathy. Conclusions. Notwithstanding the numerous research data on hypertrophic cardiomyopathy, no consensus among the authors regarding the etiology and pathogenesis of hypertrophic cardiomyopathy exists to date. Controversial data on the interrelation and sequence of disarray, myocardial hypertrophy, interstitial fibrosis, changes in the microvasculature and structural changes of the mitral valve in patients with hypertrophic cardiomyopathy hamper the search for adequate etiotropic treatment. Polymorphism of clinical and morphological manifestations of hypertrophic cardiomyopathy requires collaborative efforts to study the disease by cardiologists and pathologists.

Altered Ca2+ and Na+ Homeostasis in Human Hypertrophic Cardiomyopathy: Implications for Arrhythmogenesis.

Hypertrophic cardiomyopathy (HCM) is the most common mendelian heart disease, with a prevalence of 1/500. HCM is a primary cause of sudden death, due to an heightened risk of ventricular tachyarrhythmias that often occur in young asymptomatic patients. HCM can slowly progress toward heart failure, either with preserved or reduced ejection fraction, due to worsening of diastolic function. Accumulation of intra-myocardial fibrosis and replacement scars underlies heart failure progression and represents a substrate for sustained arrhythmias in end-stage patients. However, arrhythmias and mechanical abnormalities may occur in hearts with little or no fibrosis, prompting toward functional pathomechanisms. By studying viable cardiomyocytes and trabeculae isolated from inter-ventricular septum samples of non-failing HCM patients with symptomatic obstruction who underwent myectomy operations, we identified that specific abnormalities of intracellular Ca2+ handling are associated with increased cellular arrhytmogenesis and diastolic dysfunction. In HCM cardiomyocytes, diastolic Ca2+ concentration is increased both in the cytosol and in the sarcoplasmic reticulum and the rate of Ca2+ transient decay is slower, while the amplitude of Ca2+-release is preserved. Ca2+ overload is the consequence of an increased Ca2+ entry via L-type Ca2+-current [due to prolongation the action potential (AP) plateau], combined with a reduced rate of Ca2+-extrusion through the Na+/Ca2+ exchanger [due to increased cytosolic (Na+)] and a lower expression of SERCA. Increased late Na+ current (INaL) plays a major role, as it causes both AP prolongation and Na+ overload. Intracellular Ca2+ overload determines an higher frequency of Ca2+ waves leading to delayed-afterdepolarizations (DADs) and premature contractions, but is also linked with the increased diastolic tension and slower relaxation of HCM myocardium. Sustained increase of intracellular [Ca2+] goes hand-in-hand with the increased activation of Ca2+/calmodulin-dependent protein-kinase-II (CaMKII) and augmented phosphorylation of its targets, including Ca2+ handling proteins. In transgenic HCM mouse models, we found that Ca2+ overload, CaMKII and increased INaL drive myocardial remodeling since the earliest stages of disease and underlie the development of hypertrophy, diastolic dysfunction and the arrhythmogenic substrate. In conclusion, diastolic dysfunction and arrhythmogenesis in human HCM myocardium are driven by functional alterations at cellular and molecular level that may be targets of innovative therapies.

Late sodium current inhibitors to treat exercise-induced obstruction in hypertrophic cardiomyopathy: an in vitro study in human myocardium.

Background and PurposeIn 30–40% of hypertrophic cardiomyopathy (HCM) patients, symptomatic left ventricular (LV) outflow gradients develop only during exercise due to catecholamine‐induced LV hypercontractility (inducible obstruction). Negative inotropic pharmacological options are limited to β‐blockers or disopyramide, with low efficacy and tolerability. We assessed the potential of late sodium current (INaL)‐inhibitors to treat inducible obstruction in HCM.Experimental ApproachThe electrophysiological and mechanical responses to β‐adrenoceptor stimulation were studied in human myocardium from HCM and control patients. Effects of INaL‐inhibitors (ranolazine and GS‐967) in HCM samples were investigated under conditions simulating rest and exercise.Key ResultsIn cardiomyocytes and trabeculae from 18 surgical septal samples of patients with obstruction, the selective INaL‐inhibitor GS‐967 (0.5 μM) hastened twitch kinetics, decreased diastolic [Ca2+] and shortened action potentials, matching the effects of ranolazine (10μM). Mechanical responses to isoprenaline (inotropic and lusitropic) were comparable in HCM and control myocardium. However, isoprenaline prolonged action potentials in HCM myocardium, while it shortened them in controls. Unlike disopyramide, neither GS‐967 nor ranolazine reduced force at rest. However, in the presence of isoprenaline, they reduced Ca2+‐transient amplitude and twitch tension, while the acceleration of relaxation was maintained. INaL‐inhibitors were more effective than disopyramide in reducing contractility during exercise. Finally, INaL‐inhibitors abolished arrhythmias induced by isoprenaline.Conclusions and ImplicationsRanolazine and GS‐967 reduced septal myocardium tension during simulated exercise in vitro and therefore have the potential to ameliorate symptoms caused by inducible obstruction in HCM patients, with some advantages over disopyramide and β‐blockers.

Ranolazine Prevents Phenotype Development in a Mouse Model of Hypertrophic Cardiomyopathy.

Current therapies are ineffective in preventing the development of cardiac phenotype in young carriers of mutations associated with hypertrophic cardiomyopathy (HCM). Ranolazine, a late Na+ current blocker, reduced the electromechanical dysfunction of human HCM myocardium in vitro. To test whether long-term treatment prevents cardiomyopathy in vivo, transgenic mice harboring the R92Q troponin-T mutation and wild-type littermates received an oral lifelong treatment with ranolazine and were compared with age-matched vehicle-treated animals. In 12-months-old male R92Q mice, ranolazine at therapeutic plasma concentrations prevented the development of HCM-related cardiac phenotype, including thickening of the interventricular septum, left ventricular volume reduction, left ventricular hypercontractility, diastolic dysfunction, left-atrial enlargement and left ventricular fibrosis, as evaluated in vivo using echocardiography and magnetic resonance. Left ventricular cardiomyocytes from vehicle-treated R92Q mice showed marked excitation-contraction coupling abnormalities, including increased diastolic [Ca2+] and Ca2+ waves, whereas cells from treated mutants were undistinguishable from those from wild-type mice. Intact trabeculae from vehicle-treated mutants displayed inotropic insufficiency, increased diastolic tension, and premature contractions; ranolazine treatment counteracted the development of myocardial mechanical abnormalities. In mutant myocytes, ranolazine inhibited the enhanced late Na+ current and reduced intracellular [Na+] and diastolic [Ca2+], ultimately preventing the pathological increase of calmodulin kinase activity in treated mice. Owing to the sustained reduction of intracellular Ca2+ and calmodulin kinase activity, ranolazine prevented the development of morphological and functional cardiac phenotype in mice carrying a clinically relevant HCM-related mutation. Pharmacological inhibitors of late Na+ current are promising candidates for an early preventive therapy in young phenotype-negative subjects carrying high-risk HCM-related mutations.

Successful MACE risk stratification in hypertrophic cardiomyopathy patients using different 2D speckle-tracking TTE approaches

PurposeWe performed 2D speckle tracking transthoracic-echocardiography (TTE) to compare the ability to predict occurrence of major adverse cardiac events (MACE) between global longitudinal strain (GLS) and circumferential strain (GCS) in left ventricular (LV) myocardium in hypertrophic cardiomyopathy (HCM) patients without obstructed coronary arteries. MethodsWe measured 2D LV GLS and GCS retrospectively by TTE within 13months of performance of cardiac CT in 41 consecutive symptomatic HCM patients (27 males; 60±13years) without obstructed coronary arteries on CT. Patients were followed up for a median period of 30months. ResultsMACE occurred in 7 (17%) patients. The Cox proportional hazard model for univariate analysis revealed that 2D LV GLS (hazard ratio (HR) 1.89, P=0.019) was a significant predictor of MACE but GCS (HR 1.07, P=0.118) was not. The Cox model for multivariate analysis revealed that 2D LV GLS (hazard ratio 2.144, P=0.013) was a significant predictor for MACE. In receiver operating characteristic (ROC) curves at a best cut-off of −9.65% (2D LV GLS) and −29.35% (2D LV GCS), the sensitivity and specificity for MACE occurrence were 100% and 64.7% (2D LV GLS) and 100% and 47.1% (2D LV GCS), respectively. Kaplan Meier analysis revealed significant differences in MACE occurrence during the follow-up period between ≦−9.65 and >9.65% of 2D LV GLS (P=0.004) and ≦−29.35 and >−29.35% of 2D LV GCS (P=0.017). ConclusionsBoth 2D LV GLS and GCS (2D LV GLS>GCS) on TTE can predict poor prognosis in HCM patients without obstructed coronary arteries.

T1 mapping in children and young adults with hypertrophic cardiomyopathy.

To assess the global and segmental left ventricular (LV) native T1 and extracellular volume fraction (ECV) in children and young adults with hypertrophic cardiomyopathy (HCM) compared to a control cohort. The study population included 21 HCM patients (mean 14.1 ± 4.6 years) and 21 controls (mean 15.7 ± 1.5 years). Native modified Look-Locker inversion recovery sequence was performed before and after contrast injection in 3 short axis planes. Global and segmental LV native T1 and ECV were quantified and compared between HCM patients and controls. Mean native T1 in HCM patients and controls was 1020.4 ± 41.2 and 965.6 ± 30.2ms respectively (p < 0.0001). Hypertrophied myocardium had significantly higher native global T1 and global ECV compared to non-hypertrophied myocardium in HCM (p < 0.0001, = 0.14 and 0.048, = 0.01 respectively). In a subset of patients, ECV was higher in LV segments with LGE compared to no LGE (p < 0.0001). No significant correlation was identified between global native T1 and ECV and parameters of LV structure and function. Native T1 cut-off of 987ms provided the highest sensitivity (95 %) and specificity (91 %) to separate HCM patients from controls. Global and segmental native T1 are elevated in HCM patients. LV segments with hypertrophy and/or LGE had higher ECV in a subset of HCM patients. LV native T1 and ECV do not correlate with parameters of LV structure and function. T1 in children and young adults may be used as a non-invasive tool to assess for HCM and related fibrosis.

Native T1 mapping in children and young adults with hypertrophic cardiomyopathy

To assess the global and segmental left ventricular (LV) native T1 and extracellular volume fraction (ECV) in children and young adults with hypertrophic cardiomyopathy (HCM) compared to a control cohort. The study population included 21 HCM patients (mean 14.1 ± 4.6 years) and 21 controls (mean 15.7 ± 1.5 years). Native modified Look-Locker inversion recovery sequence was performed before and after contrast injection in 3 short axis planes. Global and segmental LV native T1 and ECV were quantified and compared between HCM patients and controls. Mean native T1 in HCM patients and controls was 1020.4 ± 41.2 and 965.6 ± 30.2 ms respectively (p < 0.0001). Hypertrophied myocardium had significantly higher native global T1 and global ECV compared to non-hypertrophied myocardium in HCM (p < 0.0001, = 0.14 and 0.048, = 0.01 respectively). In a subset of patients, ECV was higher in LV segments with LGE compared to no LGE (p < 0.0001). No significant correlation was identified between global native T1 and ECV and parameters of LV structure and function. Native T1 cut-off of 987 ms provided the highest sensitivity (95 %) and specificity (91 %) to separate HCM patients from controls. Global and segmental native T1 are elevated in HCM patients. LV segments with hypertrophy and/or LGE had higher ECV in a subset of HCM patients. LV native T1 and ECV do not correlate with parameters of LV structure and function. T1 in children and young adults may be used as a non-invasive tool to assess for HCM and related fibrosis.