Hypertrophic Cardiomyopathy Heart 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.

10 Pre-clinical studies of sotagliflozin in hypertrophic cardiomyopathy

OBJECTIVES/GOALS: Study the regulatory role of sodium glucose co-transporter 1 (SGLT1) in cardiomyocytes and the therapeutic potential of sotagliflozin in hypertrophic cardiomyopathy (HCM) by (a) quantifying SGLT1 expression in HCM and (b) examining the impact of sotagliflozin on cardiac mechanics. METHODS/STUDY POPULATION: * Use Western Blot in cardiac tissue from HCM and non-HCM patients and pre-existing RNA seq and proteomics datasets to quantify SGLT1 levels in HCM. Hypothesis: SGLT1 is upregulated in HCM * Determine how SGLT1/2 inhibition by sotagliflozin will affect cardiac mechanics using living myocardial slice (LMS) preparations. A vibratome creates 200um-thick slices from (a) failing HCM heart explants, (b) septal myectomy samples from HCM patients, and (c) nonfailing rejected donor hearts. LMS are mounted on a force transducer and work-loops are stimulated under varying pre- and after-loads. Collecting baseline and post-drug work loops allows each slice to function as its own control. Hypothesis: sotagliflozin will improve diastolic mechanics by reducing stiffness in the end-diastolic pressure-volume relationship RESULTS/ANTICIPATED RESULTS: * Preliminary results from RNA seq data indicate that SLC5A1 mRNA (encoding gene for SGLT1) is significantly decreased in HCM. No proteomics study examined thus far has detected SLC5A1, indicating that overall SGLT1 levels in cardiac tissue are quite low. We will examine SGLT1 levels in our own HCM and non-HCM tissue samples with both mass-spectrometry and Western Blot. * We analyze six slices from each heart and expect 15 donor hearts and 15 HCM hearts/myectomy samples. We visualize the work loop by plotting stress/strain. Stress/strain at mitral valve closure represents exponential end diastolic pressure-volume relationship; Stress/strain at aortic valve closure represents linear end systolic pressure volume relationship. A two-sample paired t-test will compare change in stiffness and elastance. DISCUSSION/SIGNIFICANCE: This project contributes to a growing body of research surrounding the currently unknown cardioprotective mechanism of SGLT 1/2 inhibitors, furthers the technique of using living myocardial slices to study cardiac mechanics, and supports a trial examining sotagliflozin in HCM, for which disease modifying therapy remains a prevailing unmet need.

Profiling cardiomyocytes at single cell resolution reveals COX7B could be a potential target for attenuating heart failure in cardiac hypertrophy

Cardiac hypertrophy can develop to end-stage heart failure (HF), which inevitably leading to heart transplantation or death. Preserving cardiac function in cardiomyocytes (CMs) is essential for improving prognosis in hypertrophic cardiomyopathy (HCM) patients. Therefore, understanding transcriptomic heterogeneity of CMs in HCM would be indispensable to aid potential therapeutic targets investigation. We isolated primary CM from HCM patients who had extended septal myectomy, and obtained transcriptomes in 338 human primary CM with single-cell tagged reverse transcription (STRT-seq) approach. Our results revealed that CMs could be categorized into three subsets in nonfailing HCM heart: high energy synthesis cluster, high cellular metabolism cluster and intermediate cluster. The expression of electron transport chain (ETC) was up-regulated in larger-sized CMs from high energy synthesis cluster. Of note, we found the expression of Cytochrome c oxidase subunit 7B (COX7B), a subunit of Complex IV in ETC had trends of positively correlation with CMs size. Further, by assessing COX7B expression in HCM patients, we speculated that COX7B was compensatory up-regulated at early-stage but down-regulated in failing HCM heart. To test the hypothesis that COX7B might participate both in hypertrophy and HF progression, we used adeno associated virus 9 (AAV9) to mediate the expression of Cox7b in pressure overload-induced mice. Mice in vivo data supported that knockdown of Cox7b would accelerate HF and Cox7b overexpression could restore partial cardiac function in hypertrophy. Our result highlights targeting COX7B and preserving energy synthesis in hypertrophic CMs could be a promising translational direction for HF therapeutic strategy.

Abstract P1025: Hsp70 Co-chaperones Regulate Sarcomeric Proteostasis In Hypertrophic Cardiomyopathy

Significance: Recent Genome Wide Association Studies (GWAS) identified non-sarcomeric variants in hypertrophic cardiomyopathy (HCM) with three of the top 10 variant loci in or near genes that encode for co-chaperones of HSP70: BAG3, DNAJC18 and HSPB7. These variants are also present in dilated cardiomyopathy (DCM), but have an opposing effect on cardiac function, leading us to hypothesize that GWAS variants in HSP70 co-chaperones can affect the proteostasis of contractile proteins in the HCM heart. As a first step, we determined the effects each HSP70 co-chaperone knockdown (KD) had on sarcomeric and z-disc protein expression and the poly-ubiquitinated state of cardiomyocyte-specific proteins. Methods and Results: Transduction of human iPSC-CMs (iPSC-CMs) with adenoviral vectors driving shRNA expression against BAG3, DNAJC18, HSPB7, or scramble (control) yielded transduction efficiencies > 75% and >80% reduction in target transcript 4 days post-transduction. BAG3 KD increased poly-ubiquitinated proteins by 38+/-9% (p<0.001) and reduced steady state expression of sarcomeric and z-disc proteins, including: MyBP-C (p<0.0001), actin (p<0.0001), cardiac troponin I (p<0.05), tropomyosin (TPM1) (p<0.01), myosin light chain 3 (MYL3) (p<0.0001), filamin C (p<0.05), and alpha-actinin-2 (p<0.0001). DNAJC18 KD increased poly-ubiquitinated protein by 66+/-17% (p<0.01) but did not impact sarcomere protein expression. Conversely, HSPB7 KD reduced poly-ubiquitinated proteins by 21+/-7% (p<0.01) and increased protein expression of MyBP-C (p<0.01), TPM1 (p<0.05), and myosin light chain 2 (p<0.05). DNAJC18 KD increased BAG3 and HSPB7 protein expression levels by ~2-fold (p<0.001) without increasing transcript levels, suggesting BAG3 and HSPB7 may be protein clients of DNAJC18. Conclusions: HSP70 co-chaperones that have an established genetic association with human HCM play an important role in cardiomyocyte proteostasis. Multiple sarcomeric and z-disc proteins appear to be clients of BAG3, while BAG3 and HSPB7 themselves may be clients of DNAJC18. Targeting this axis could be therapeutic for patients with HCM that possess genetic variants in sarcomeric proteins.

Is Congenital Muscular Mitral-Aortic Discontinuity Another Feature of Obstructive Hypertrophic Cardiomyopathy? A Pathology Validation Study

Hypertrophic cardiomyopathy (HCM) is an inherited myocardial disease at risk of sudden cardiac death and heart failure, even requiring heart transplantation. A “muscular mitral-aortic discontinuity” has been reported during surgery in the obstructive form. We aimed to validate these findings through pathological analysis of HCM heart specimens from the cardiovascular pathology tissue registry. Hearts with septal asymmetric HCM from sudden cardiac death, other causes of death, or heart transplantation were included. Sex-matched and age-matched patients without HCM served as controls. Gross and histologic analysis of the mitral valve (MV) apparatus and the mitral-aortic continuity were performed. Thirty HCM hearts (median age, 29.5 years; 15 men) and 30 controls (median age, 30.5 years; 15 men) were studied. In HCM hearts, a septal bulging was present in 80%, an endocardial fibrous plaque in 63%, a thickening of the anterior MV leaflet in 56.7%, and an anomalous insertion of papillary muscle in 10%. All cases but 1 (97%) revealed a myocardial layer overlapping the mitral-aortic fibrous continuity on the posterior side, corresponding to the left atrial myocardium. A negative correlation between the length of this myocardial layer and the age and the anterior MV leaflet length was found. The length did not differ between HCM and controls.Pathologic study of obstructive HCM hearts does not confirm the existence of a "muscular mitral-aortic discontinuity". An extension of left atrial myocardium, overlapping posteriorly the intervalvular fibrosa, is rather visible, and its length decreases with age, possibly as a consequence of left atrial remodeling. Our study highlights the fundamental role of thorough gross examination and the value of organ retention for further analysis in order to validate new surgical and imaging findings.

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.

Protein densitometry profiling in mouse hearts carrying an HCM cardiac troponin T mutation.

Hypertrophic cardiomyopathy (HCM) is one of the most common genetic cardiac diseases caused by mutations in over a dozen genes encoding sarcomere-associated proteins. The cardiac troponin T (TnT) I79N mutation has been linked to familial HCM in humans and in transgenic mice expressing the mutant human TnT. Many studies from molecular to physiological assays have shown altered cardiac myofilament performance, increased myofilament Ca2+ sensitivity, enhanced cardiac contractility, and impaired relaxation in mice carrying the cTnT-I79N mutation. However, the overall protein expression profile by which a gene mutation causes the disease pathogenesis is still not well understood. In this study we aim to apply protein densitometry profiling of myocardial tissue from non-transgenic (NTg) mice and transgenic mice bearing cTnT-I79N to explore global alterations in cellular and myofibrillar protein expression levels. We used the traditional 1D SDS-PAGE in conjunction with protein identification by mass spectrometry. Whole cell protein extract was obtained from seven hearts of NTg mice and seven HcTnT-I79N mice of 5 months of age. After electrophoresis, gels were stained with Coomassie brilliant blue and imaged for densitometry analysis. ImageJ was used to determine the relative peak areas of the different gel bands. From cell extract, we observed a wide range of protein abundances including the presence of myofilament proteins. Thus our next goal is to extract myofibril proteins to acquire more distinct peaks, and to determine the myofibrillar protein ratios in NTg and I79N hearts. Secondary confirmation of each myofibrillar protein expression levels will be done with western blot and mass spectrometry. This work on the analysis of the major proteins in the HCM heart can provide new insights into cellular mechanisms involved in cardiac dysfunction.

In-Hospital Outcomes of Acute Ischemic Stroke in Patients With Hypertrophic Cardiomyopathy

ObjectiveTo investigate the in-hospital outcomes of acute ischemic stroke in patients with hypertrophic cardiomyopathy (HCM). Patients and MethodsUsing weighted discharge data from the National Inpatient Sample, we identified 5804 nonelective hospitalizations for ischemic stroke in adult patients with HCM between 2011 and 2017. For comparison, 58,179 hospitalizations for ischemic stroke in adult patients without HCM were selected as controls using the simple random sampling method. ResultsCompared with the patients without HCM, those with HCM had a higher prevalence of hyperlipidemia (62.4% vs 57.5%, respectively, P<.001) and chronic heart failure (25.4% vs 13.6%, respectively, P<.001) but a lower prevalence of diabetes (28.2% vs 34.9%, respectively, P<.001) and hypertension (42.9% vs 53.4%, respectively, P<.001). Atrial fibrillation was documented in 45.1% (n=2617) of the patients with HCM. However, only 28.0% (n=733) of these patients had long-term use of anticoagulants. The in-hospital death rate among the patients with HCM was 6.3% (n=368), which was significantly higher than that in the patients without HCM (4.1%, P<.001). Having HCM (odds ratio [OR], 1.35; P<.001), atrial fibrillation (OR, 2.08; P<.001), and chronic heart failure (OR, 1.65; P<.001) were significant predictors of in-hospital death. In patients with HCM who were discharged alive, 50.0% were transferred to skilled nursing facilities compared with 45.3% of those without HCM (P<.001). ConclusionThe prognosis of acute ischemic stroke is worse in patients with HCM than in those without HCM. These findings emphasize the importance of aggressive treatment of predisposing factors for stroke in patients with HCM, especially atrial fibrillation.

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.

Metoprolol Improves Left Ventricular Longitudinal Strain at Rest and during Exercise in Obstructive Hypertrophic Cardiomyopathy

Patients with obstructive hypertrophic cardiomyopathy (HCM) often experience symptoms of heart failure upon exertion despite having normal left ventricular (LV) ejection fractions. Longitudinal strain (LS) may be a more sensitive marker of systolic dysfunction in patients with LV hypertrophy. The aims of this study were to characterize LV segmental LS and global LS (GLS) at rest and during exercise and to assess if first-line treatment with β-blockers improves LV systolic performance. Twenty-nine patients with obstructive HCM and New York Heart Association functional class≥II symptoms were enrolled in a double-blind, placebo-controlled, randomized crossover trial. Patients received metoprolol 150mg or placebo for two consecutive 2-week periods in random order. Echocardiographic assessment with speckle-tracking-derived LS was performed at rest and during peak exercise at the end of each treatment period. During placebo treatment, resting values of segmental LS showed an apical-basal difference of -10.3% (95% CI, -12.7% to -7.8%; P<.0001), with a severely abnormal value of the basal segment of -9.3±4.2%. Treatment with metoprolol was associated with more negative LS values of the apical segment (-2.8%; 95% CI, -4.2% to -1.3%; P<.001) and the mid segment (-1.1%; 95% CI, -2.0% to -0.3%; P=.007). During peak exercise there was a deterioration in LV GLS, but treatment with metoprolol was associated with more negative peak exercise LV GLS (-1.3 %; 95% CI, -2.6% to -0.1%; P=.03). Systolic performance assessed by LV GLS showed impaired values at rest and during exercise, with severely depressed values of the basal and mid segments. Treatment with metoprolol improved LV GLS upon exercise, indicating a beneficial effect of β-blocker treatment on LV systolic function.

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.

Effects of Metoprolol on Exercise Hemodynamics in Patients With Obstructive Hypertrophic Cardiomyopathy

BackgroundThe relationship between exercise hemodynamics, loading conditions, and medical treatment in patients with obstructive hypertrophic cardiomyopathy (HCM) is incompletely understood. ObjectivesThis study aimed to investigate the effect of metoprolol on invasive hemodynamic parameters at rest and during exercise in patients with obstructive HCM. MethodsThis randomized, double-blind, placebo-controlled crossover trial enrolled 28 patients with obstructive HCM and New York Heart Association functional class ≥II. Patients were randomized to initiate either metoprolol 150 mg or placebo for 2 consecutive 2-week periods. Right-heart catheterization and echocardiography were performed at rest and during exercise at the end of each treatment period. The primary outcome was the difference in pulmonary capillary wedge pressure (ΔPCWP) between peak exercise and rest. ResultsNo treatment effect on ΔPCWP was observed between metoprolol and placebo treatment (21 ± 9 mm Hg vs 23 ± 9 mm Hg; P = 0.12). At rest, metoprolol lowered heart rate (P < 0.0001), left ventricular outflow tract (LVOT) gradient (P = 0.01), and increased left ventricular end-diastolic volume (P = 0.02) and stroke volume (SV) (+6.4; 95% CI: 0.02-17.7; P = 0.049). During peak exercise, metoprolol was associated with a lower heart rate (P < 0.0001), a lower LVOT gradient (P = 0.0005), lesser degree of mitral regurgitation (P = 0.004), and increased SV (+9 mL; 95% CI: 2-15 mL; P = 0.008). ConclusionsIn patients with obstructive HCM, exercise was associated with an abnormal rise in PCWP, which was unaffected by metoprolol. However, metoprolol increased SV at rest and peak exercise following changes in end-diastolic volume, LVOT gradient, and degree of mitral regurgitation. (The Effect of Metoprolol in Patients With Hypertrophic Obstructive Cardiomyopathy [TEMPO]; NCT03532802)

Randomized Trial of Metoprolol in Patients With Obstructive Hypertrophic Cardiomyopathy

BackgroundThe use of β-adrenergic receptor blocking agents in symptomatic patients with obstructive hypertrophic cardiomyopathy (HCM) rests on clinical experience and observational cohort studies. ObjectivesThis study aimed to investigate the effects of metoprolol on left ventricular outflow tract (LVOT) obstruction, symptoms, and exercise capacity in patients with obstructive HCM. MethodsThis double-blind, placebo-controlled, randomized crossover trial enrolled 29 patients with obstructive HCM and New York Heart Association (NYHA) functional class II or higher symptoms from May 2018 to September 2020. Patients received metoprolol or placebo for 2 consecutive 2-week periods in random order. The effect parameters were LVOT gradients, NYHA functional class, Canadian Cardiovascular Society (CCS) angina class, Kansas City Cardiomyopathy Questionnaire Overall Summary Score (KCCQ-OSS), and cardiopulmonary exercise testing. ResultsCompared with placebo, the LVOT gradient during metoprolol was lower at rest (25 mm Hg [interquartile range (IQR): 15-58 mm Hg] vs 72 mm Hg [IQR: 28-87 mm Hg]; P = 0.007), at peak exercise (28 mm Hg [IQR: 18-40 mm Hg] vs 62 mm Hg [IQR: 31-113 mm Hg]; P < 0.001), and postexercise (45 mm Hg [IQR: 24-100 mm Hg] vs 115 mm Hg [IQR: 55-171 mm Hg]; P < 0.0001). During metoprolol treatment, 14% of patients were in NYHA functional class III or higher compared with 38% of patients receiving placebo (P < 0.01). Similarly, no patients were in CCS class III or higher during metoprolol treatment compared with 10% during placebo treatment (P < 0.01). These findings were confirmed by higher KCCQ-OSS during metoprolol treatment (76.2 ± 16.2 vs 73.8 ± 19.5; P = 0.039). Measures of exercise capacity, peak oxygen consumption, and N-terminal pro–B-type natriuretic peptide did not differ between the study arms. ConclusionsCompared with placebo, metoprolol reduced LVOT obstruction at rest and during exercise, provided symptom relief, and improved quality of life in patients with obstructive HCM. Maximum exercise capacity remained unchanged. (The Effect of Metoprolol in Patients with Hypertrophic Obstructive Cardiomyopathy [TEMPO]; NCT03532802)

Abstract 12535: The Hemodynamic Response to Exercise in Patients With Obstructive Hypertrophic Cardiomyopathy and the Effect of Metoprolol

Introduction: Patients with obstructive hypertrophic cardiomyopathy (HCM) frequently experience advanced heart failure symptoms at low levels of physical activity. The relationship between symptoms and loading conditions during exercise is incompletely understood. Whether standard treatment with beta-blockers affects exercise hemodynamics is unknown. Objectives: The aim of this study was to investigate the invasive hemodynamic response to exercise in moderately symptomatic patients with obstructive HCM, and how treatment with metoprolol affects this response. Method: This double-blinded, placebo-controlled, randomized crossover trial enrolled 28 patients with obstructive HCM and New York Heart Association functional class ≥ II from May 2018 to September 2020. Patients received metoprolol or placebo for two consecutive two-week periods in random order. During each treatment period, patients underwent right-heart catheterization at rest and during exercise. The primary outcome was the difference in pulmonary capillary wedge pressure (ΔPCWP) between peak exercise and rest. Results: There was no treatment effect on Δ PCWP between metoprolol and placebo treatment (21(9) mmHg versus 23(9) mmHg; p = 0.12). When comparing metoprolol to placebo treatment, there was no significant difference in PCWP at rest (15 (6) mmHg versus 13 (5) mmHg; p = 0.06) or at peak exercise (35 (12) mmHg versus 37 (10) mmHg; p = 0.38). At peak exercise, metoprolol treatment was associated with a higher stroke volume (101 (24) ml versus 92 (21) ml; p &lt; 0.01), a 25% lower heart rate (107 (19) beats/min versus 139 (23) beats/min; p &lt; 0.0001), and subsequently a lower cardiac output (10.8 (3.3) L/min versus 12.8 (3.2) L/min; p &lt; 0.0001). Conclusion: Exercise in patients with obstructive HCM is associated with a severe increase in left-sided filling pressures which are not affected by metoprolol treatment. Despite increased stroke volume during metoprolol treatment, cardiac output is reduced at peak exercise.

Abstract 13342: Transcriptional Profiling of Surgical Myectomy Tissue in Patients With Hypertrophic Cardiomyopathy Reveals Genotype Independent Counterregulatory Alterations in Hypertrophy Pathways

Introduction: Hypertrophic cardiomyopathy (HCM) is one of the most common genetic heart diseases characterized by asymmetric left ventricular hypertrophy (LVH) and vast clinical and genetic heterogeneity. Several transcriptional studies in HCM heart tissues have shown severe alterations in gene expression. However, these earlier studies relied on microarray technology or were limited by small sample size or lack of genotype-specific analyses. Methods: We obtained flash-frozen cardiac tissue from patients with HCM undergoing surgical myectomy/septal reduction therapy for relief of left ventricular outflow tract obstruction. RNA-sequencing (RNAseq) was performed using paired-end index reading on 97 myectomy tissues (44 female [45%]; mean age at surgery of 47 ± 18 years) and 23 control tissues (10 female [43%]; mean age at death of 43 ± 12 years) to identify differentially expressed genes (DEGs) using edgeR and pathways in HCM using Ingenuity Pathway Analysis. Additionally, genome sequencing (GS) was performed and HCM patients were divided into genotype-based subgroups to compare the transcriptional profile across different genotypes. Results: Overall, 43% had a pathogenic, HCM-associated variant including 23% with MYBPC3-HCM and 15% with MYH7-HCM. Among the 15,634 genes expressed in the cardiac tissue,1,246 genes (8%) were upregulated and 738 genes (3%) were downregulated significantly in HCM vs. controls. Pathway analysis showed alterations in 126 pathways with downregulation of 44 pathways and upregulation of 1 pathway. There were notable transcriptional alterations of most canonical, pro-hypertrophic pathways, including statistically and biologically significant downregulation of five pathways [-log (BH p-value)≥ 1.3; Z-score≤ -2]: ERK/MAPK, p38 MAPK, ERK5, IL6, and NF-κB signaling. Far less DEGs were observed between genotypic subgroups, with only 37 DEGSs identified between sarcomere positive- and genotype negative-HCM. Conclusions: At the time of surgical myectomy, the ventricular myocardium’s transcriptome, independent of genotype, reveals widespread downregulation of pro-hypertrophic pathways. Whether these counter regulatory measures can be targeted therapeutically warrants further investigation.

Clinical effects of metoprolol in obstructive hypertrophic cardiomyopathy (TEMPO). A randomized, double-blinded, placebo-controlled crossover trial

Abstract Background Treatment with beta blockers (BB) has been used for symptomatic relief in patients with obstructive hypertrophic cardiomyopathy (HCM) for decades. Even so, the guideline recommendation for the use of BB rests on expert opinions and observational cohort studies. Providing comprehensive high-quality data on the effects of BB in obstructive HCM is essential, especially in the context of newly developed pharmacological treatment strategies specifically targeting this disease (1). Purpose The study aimed to investigate the effects of metoprolol on left ventricular outflow tract (LVOT) obstruction, symptoms, and exercise capacity in patients with obstructive HCM. Methods This double-blinded, placebo-controlled, randomized crossover trial enrolled 30 patients with obstructive HCM and New York Heart Association (NYHA) class ≥ II symptoms from 1 May 2018 to 1 September 2020. Patients received metoprolol or placebo for two consecutive two-week periods in random order. The effect parameters were LVOT gradients, NYHA class, Canadian Cardiovascular Society (CCS) grading angina class, Kansas City Cardiomyopathy Questionnaire Overall Summary Score (KCCQ-OSS), and cardiopulmonary exercise testing. Results Compared with placebo, the LVOT gradient during metoprolol was lower at rest (25 [15–58] mmHg versus 72 [28–87] mmHg; p=0.007), at peak exercise (28 [18–40] mmHg versus 62 [31–113] mmHg; p&amp;lt;0.001), and post-exercise (45 [24–100] mmHg versus 115 [55–171] mmHg; p&amp;lt;0.0001) (figure 1). During metoprolol treatment, 14% of patients were in NYHA class III compared with 38% on placebo (p&amp;lt;0.01). Likewise, no patients were in CCS class ≥ III during metoprolol compared with 10% during placebo (p&amp;lt;0.01). These findings were confirmed by a higher KCCQ-OSS score during metoprolol (76.2 (16.2) versus 73.8 (19.5), p=0.039) (figure 2). Peak oxygen consumption did not differ between study arms. Conclusion Compared with placebo, metoprolol reduced LVOT obstruction at rest and during exercise, provided symptom relief, and improved quality of life in patients with obstructive HCM. However, exercise capacity remained unchanged. Findings from the present study support the guideline recommendations that BB should be the first drug of choice in patients with obstructive HCM who develop symptoms. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Novo nordic foundation, Skibsreder Per Henriksen, R. og hustrus Foundation

Poster: Cardiovascular magnetic resonance analysis for discrimination between hypertensive heart disease and hypertrophic cardiomyopathy

It may be difficult to differentiate hypertrophic cardiomyopathy (HCM) from hypertensive heart disease (HHD) especially when left ventricular wall thickness (LVWT) ≥ 15 mm. Because cardiovascular magnetic resonance (CMR) has emerged as an efficient technique to characterise morphologic, functional and tissue abnormalities, we investigate the discriminatory capacity of this technique by analysing different imaging markers in HCM and in HHD. A total of 60 HCM patients (group 1) and 60 HHD subjects with left ventricular wall thickness ≥ 15 mm without ischemic or other cardiac pathology (group 2) underwent CMR. No differences were noted between the 2 groups with regards to mean ages, BMI, gender and creatinine clearance. The 2 groups had similar indexed LV mass (group 1: 107 ± 11 g/m 2 vs. group 2: 104 ± 13 g/m 2 , P > 0.05) but patients with HCM had higher LVWT compared with HHD patients (21.5 ± 3 mm vs. 16.3 ± 1.2 mm, P < 0.001). Complete systolic anterior motion of the mitral valve (SAM) was frequent in group 1 patients while totally absent in group 2 (38% vs. 0%, P < 0.0001). Late gadolinium enhancement (LGE) was significantly predominant in HCM patients (76% vs. 14%, P < 0.0001). Compared with HHD group, native T1 was also significantly higher in HCM patients (1181 ± 36 ms vs. 1048 ± 40 ms, P < 0.001). In multivariate analysis, presence of SAM and native T1 remained significant predictors of HCM. These observations underscore the important role for CMR in the assessment of patients with HCM. CMR has several tools providing novel information in accurate discrimination between HCM and hypertensive heart disease.

A novel homozygous TPM1 mutation in familial pediatric hypertrophic cardiomyopathy and in silico screening of potential targeting drugs.

Familial hypertrophic cardiomyopathy (HCM) is the most common genetic cardiac disease. While sarcomeric gene mutations explain many HCM cases, the genetic basis of about half of HCM cases remains elusive. Here we aimed to identify the gene causing HCM in a non-consanguineous Saudi Arabian family with affected family members and a history of sudden death. The impact of the identified mutation on protein structure and potential drug targets were evaluated in silico. Triplets (two HCM subjects and one patent ductus arteriosus (PDA) case) and unaffected parents were screened by targeted next-generation sequencing (NGS) for 181 candidate cardiomyopathy genes. In silico structural and functional analyses, including protein modeling, structure prediction, drug screening, drug binding, and dynamic simulations were performed to explore the potential pathogenicity of the variant and to identify candidate drugs. A homozygous missense mutation in exon 1 of TMP1 (assembly GRCh37-chr15: 63340781; G>A) was identified in the triplets [two HCM and one patent ductus arteriosus (PDA)] that substituted glycine for arginine at codon 3 (p.Gly3Arg). The parents were heterozygous for the variant. The mutation was predicted to cause a significant and deleterious change in the TPM1 protein structure that slightly affected drug binding, stability, and conformation. In addition, we identified several putative TPM1-targeting drugs through structure-based in silico screening. TPM1 mutations are a common cause of HCM and other congenital heart defects. To date, TPM1 has not been associated with isolated PDA; to our knowledge, this is the first report of the homozygous missense variation p.Gly3Arg in TPM1 associated with familial autosomal recessive pediatric HCM and PDA. The identified candidate TPM1 inhibitors warrant further prospective investigation.

P311Hypertrophic cardiomyopathy and other forms of left ventricular hypertrophy. The P wave can make the difference

Abstract Background Structural disarray of hypertrophied myocytes and interstitial fibrosis characterize hypertrophic cardiomyopathy (HCM). These morphological changes also affect atrial myocytes and, together with hemodynamic alterations because of HCM, may lead to atrial cardiomyopathy. Purpose To investigate the incremental value of P-wave parameters to differentiate left ventricular hypertrophy (LVH) because of HCM from LVH in hypertensive heart disease (HHD) and athletes heart. Methods In a prospective study, we compared electrocardiographic (including signal-averaged ECG of the P wave) and echocardiographic data of patients with HCM, HHD and athletes heart. We developed a predictive model with a simple scoring system to identify HCM. Results We compared data of 27 patients with HCM (70% males, 49.8 ± 14.5 years), 324 patients with HHD (52% males, 74.8 ± 5.5 years), and 215 subjects with athletes heart (72% males, 42.3 ± 7.5). The table shows the significant differences among the 3 groups. We included the following parameters into a predictive score to differentiate HCM from other forms of LVH: QRS width (&amp;gt;88ms = 1 point), P-wave integral (&amp;gt;688µVs = 1 point) and septum thickness (&amp;gt;12mm = 2 points). A score &amp;gt;2 (Youden index 0.626) correctly classified HCM in 81% of the cases with a sensitivity and specificity of 82% an 81%, respectively. Conclusion Differentiation of HCM from other forms of LVH is improved by including atrial parameters. A simple scoring system including septum thickness, QRS width and P wave integral allowed identification of patients with HCM with a sensitivity and specificity of &amp;gt;80%. This score needs to be validated prospectively. Table 1 HCM HHD Athletes P-value HCM vs HHD* HCM vs Athletes* 95%-CI P-value 95%-CI P-value P-wave duration [ms] 152.7 ± 25.8 143.9 ± 16.5 133.5 ± 14.2 &amp;lt;0.001 -16.9 -24.6 to -9.1 &amp;lt;0.001 -16.3 -22.7 to -9.9 &amp;lt;0.001 P-wave integral [µVs] 850.4 ± 272.4 672.0 ± 235.4 773.1 ± 260.1 &amp;lt;0.001 -198.6 -320.8 to -76.3 0.002 -68.2 -169.7 to 33.2 0.187 QRS [ms] 110.3 ± 27.3 96.9 ± 20.3 95.1 ± 9.8 &amp;lt;0.001 -16.4 -24.7 to -8.1 &amp;lt;0.001 -13.8 -20.8 to -6.9 &amp;lt;0.001 QTc [ms] 447.9 ± 27.2 438.6 ± 24.5 414.0 ± 22.9 &amp;lt;0.001 -21.1 -32.7 to -9.5 &amp;lt;0.001 -30.8 -40.5 to -21.2 &amp;lt;0.001 LVMMI [g/m2] 153.6 ± 55.5 133.5 ± 30.3 98.6 ± 19.7 &amp;lt;0.001 -15.3 -29.7 to -0.9 0.038 -56.1 -67.7 to -44.6 &amp;lt;0.001 IVS [ms] 16.8 ± 4.2 11.8 ± 2.2 10.3 ± 1.5 &amp;lt;0.001 -5.2 -6.3 to -4.1 &amp;lt;0.001 -6.4 -7.3 to -5.6 &amp;lt;0.001 LAVI [ml/m2] 43.2 ± 13.9 30.5 ± 9.7 30.8 ± 9.5 &amp;lt;0.001 -14.6 -20.0 to -9.3 &amp;lt;0.001 -12.2 -16.6 to -7.9 &amp;lt;0.001 The table shows the study result after univariate and multivariate (*; adjusting for age and sex) analysis. Abstract Figure 1

Gender-specific differences in clinical profile of hypertrophic cardiomyopathy and their association with the polymorphic variant rs1739843 of the hspb7 gene

Objective. The aim of this study was to investigate gender-specific differences in the clinical profile of hypertrophic cardiomyopathy (HCM) and to determine the impact of polymorphic variant rs1739843 of the HSPB7 gene on clinical profile and outcomes in women and men with HCM. Design and methods . The study population consisted of 171 patients with HCM ≥ 18 years old. A novel disease pathway model was employed to assess clinical course of HCM. Single nucleotide polymorphism (SNP) rs1739843 of the HSPB7 gene was genotyped by allele-specific real-time polymerase chain reaction assay. Results. We found no significant gender-specific differences in clinical course of HCM in patients ≥ 18 years old during 10-year follow-up. High prevalence of T allele of rs1739843 of the HSPB7 gene was observed in women > 18 years old with HCM and chronic heart failure (CHF) with preserved ejection fraction (EF) ( ≥ 50 %) (C: Т , odds ratio (OR) = 0,213, 95 % confidence interval (CI) = 0,077-0,593, p 18 years old.