Differences in molecular phenotype in mouse and human hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is characterized by phenotypic heterogeneity. We investigated the molecular basis of the cardiac phenotype in two mouse models at established disease stage (mouse-HCM), and human myectomy tissue (human-HCM). We analyzed the transcriptome in 2 mouse models with non-obstructive HCM (R403Q-MyHC, R92W-TnT)/littermate-control hearts at 24 weeks of age, and in myectomy tissue of patients with obstructive HCM/control hearts (GSE36961, GSE36946). Additionally, we examined myocyte redox, cardiac mitochondrial DNA copy number (mtDNA-CN), mt-respiration, mt-ROS generation/scavenging and mt-Ca2+ handling in mice. We identified distinct allele-specific gene expression in mouse-HCM, and marked differences between mouse-HCM and human-HCM. Only two genes (CASQ1, GPT1) were similarly dysregulated in both mutant mice and human-HCM. No signaling pathway or transcription factor was predicted to be similarly dysregulated (by Ingenuity Pathway Analysis) in both mutant mice and human-HCM. Losartan was a predicted therapy only in TnT-mutant mice. KEGG pathway analysis revealed enrichment for several metabolic pathways, but only pyruvate metabolism was enriched in both mutant mice and human-HCM. Both mutant mouse myocytes demonstrated evidence of an oxidized redox environment. Mitochondrial complex I RCR was lower in both mutant mice compared to controls. MyHC-mutant mice had similar mtDNA-CN and mt-Ca2+ handling, but TnT-mutant mice exhibited lower mtDNA-CN and impaired mt-Ca2+ handling, compared to littermate-controls. Molecular profiling reveals differences in gene expression, transcriptional regulation, intracellular signaling and mt-number/function in 2 mouse models at established disease stage. Further studies are needed to confirm differences in gene expression between mouse and human-HCM, and to examine whether cardiac phenotype, genotype and/or species differences underlie the divergence in molecular profiles.

Discovery of TITIN Gene Truncating Variant Mutations and 5-Year Outcomes in Patients With Nonischemic Dilated Cardiomyopathy.

Genetic factors play an important role in nonischemic dilated cardiomyopathy (NIDC). However, prime opportunities remain for genetic discovery and prognostic understanding. TITIN gene truncating variant mutations (TTNtv) are of interest because of their frequent appearance in NIDC series. We sought to discover known and novel TTNtv mutations in a NIDC cohort and assess 5-year outcomes. Patients with NIDC entered into the INSPIRE Registry with ≥3 years of follow-up were studied. Whole exome sequencing (WES) was performed using an Illumina Novaseq platform. Genetic analysis used Sentieon software and the GRCh38 human reference genome. Variant calls were annotated with ClinVar. Five-year outcomes were determined by functional assessment and ejection fraction (EF) as recovered (EF ≥50%), persistent (EF 21% to 49%), or progressive (left ventricular assist device, transplant, heart failure [HF] or arrhythmic death, or EF ≤20%). The study comprised 229 NIDC patients (age = 50 ± 15 years, 58% men). TTNtv's were discovered in 27 patients with 22 unique mutations; (7 known, 15 novel). TTNtv+ patients more frequently presented with severe NIDC (EF ≤20%) (p = 0.032). By 5-year, outcomes were worse in TTNtv+ patients (p = 0.027), and patients less often recovered (11% vs. 30%). Prognosis was similar with known and novel mutations. Nongenetic (e.g., environmental) cocausal risk factors for HF were frequently present, and these factors frequently appeared to act in concert with genetic variants to precipitate clinical HF. In conclusion, our study expands the library of likely pathogenic TTN mutations and increases our understanding of their clinical impact in association with other HF risk factors.

Marked Up-Regulation of ACE2 in Hearts of Patients With Obstructive Hypertrophic Cardiomyopathy: Implications for SARS-CoV-2-Mediated COVID-19.

OBJECTIVE: To explore the transcriptomic differences between patients with hypertrophic cardiomyopathy (HCM) and controls. PATIENTS AND METHODS: RNA was extracted from cardiac tissue flash frozen at therapeutic surgical septal myectomy for 106 patients with HCM and 39 healthy donor hearts. Expression profiling of 37,846 genes was performed using the Illumina Human HT-12v3 Expression BeadChip. All patients with HCM were genotyped for pathogenic variants causing HCM. Technical validation was performed using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. This study was started on January 1, 1999, and final analysis was completed on April 20, 2020. RESULTS: Overall, 22% of the transcriptome (8443 of 37,846 genes) was expressed differentially between HCM and control tissues. Analysis by genotype revealed that gene expression changes were similar among genotypic subgroups of HCM, with only 4% (1502 of 37,846) to 6% (2336 of 37,846) of the transcriptome exhibiting differential expression between genotypic subgroups. The qRT-PCR confirmed differential expression in 92% (11 of 12 genes) of tested transcripts. Notably, in the context of coronavirus disease 2019 (COVID-19), the transcript for angiotensin I converting enzyme 2 (ACE2), a negative regulator of the angiotensin system, was the single most up-regulated gene in HCM (fold-change, 3.53; q-value =1.30×10-23), which was confirmed by qRT-PCR in triplicate (fold change, 3.78; P=5.22×10-4), and Western blot confirmed greater than 5-fold overexpression of ACE2 protein (fold change, 5.34; P=1.66×10-6). CONCLUSION: More than 20% of the transcriptome is expressed differentially between HCM and control tissues. Importantly, ACE2 was the most up-regulated gene in HCM, indicating perhaps the heart's compensatory effort to mount an antihypertrophic, antifibrotic response. However, given that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uses ACE2 for viral entry, this 5-fold increase in ACE2 protein may confer increased risk for COVID-19 manifestations and outcomes in patients with increased ACE2 transcript expression and protein levels in the heart.

Differences in microRNA-29 and Pro-fibrotic Gene Expression in Mouse and Human Hypertrophic Cardiomyopathy.

Background: Hypertrophic cardiomyopathy (HCM) is characterized by myocyte hypertrophy and fibrosis. Studies in two mouse models (R92W-TnT/R403Q-MyHC) at early HCM stage revealed upregulation of endothelin (ET1) signaling in both mutants, but TGFß signaling only in TnT mutants. Dysregulation of miR-29 expression has been implicated in cardiac fibrosis. But it is unknown whether expression of miR-29a/b/c and profibrotic genes is commonly regulated in mouse and human HCM. Methods: In order to understand mechanisms underlying fibrosis in HCM, and examine similarities/differences in expression of miR-29a/b/c and several profibrotic genes in mouse and human HCM, we performed parallel studies in rat cardiac myocyte/fibroblast cultures, examined gene expression in two mouse models of (non-obstructive) HCM (R92W-TnT, R403Q-MyHC)/controls at early (5 weeks) and established (24 weeks) disease stage, and analyzed publicly available mRNA/miRNA expression data from obstructive-HCM patients undergoing septal myectomy/controls (unused donor hearts). Results: Myocyte cultures: ET1 increased superoxide/H2O2, stimulated TGFß expression/secretion, and suppressed miR-29a expression in myocytes. The effect of ET1 on miR-29 and TGFß expression/secretion was antagonized by N-acetyl-cysteine, a reactive oxygen species scavenger. Fibroblast cultures: ET1 had no effect on pro-fibrotic gene expression in fibroblasts. TGFß1/TGFß2 suppressed miR-29a and increased collagen expression, which was abolished by miR-29a overexpression. Mouse and human HCM: Expression of miR-29a/b/c was lower, and TGFB1/collagen gene expression was higher in TnT mutant-LV at 5 and 24 weeks; no difference was observed in expression of these genes in MyHC mutant-LV and in human myectomy tissue. TGFB2 expression was higher in LV of both mutant mice and human myectomy tissue. ACE2, a negative regulator of the renin-angiotensin-aldosterone system, was the most upregulated transcript in human myectomy tissue. Pathway analysis predicted upregulation of the anti-hypertrophic/anti-fibrotic liver X receptor/retinoid X receptor (LXR/RXR) pathway only in human myectomy tissue. Conclusions: Our in vitro studies suggest that activation of ET1 signaling in cardiac myocytes increases reactive oxygen species and stimulates TGFß secretion, which downregulates miR-29a and increases collagen in fibroblasts, thus contributing to fibrosis. Our gene expression studies in mouse and human HCM reveal allele-specific differences in miR-29 family/profibrotic gene expression in mouse HCM, and activation of anti-hypertrophic/anti-fibrotic genes and pathways in human HCM.

Effect of Body Mass Index on Exercise Capacity in Patients With Hypertrophic Cardiomyopathy.

The objective of this study was to evaluate the relation between body mass index (BMI), exercise capacity, and symptoms in patients with hypertrophic cardiomyopathy (HC) and to utilize results of cardiopulmonary exercise tests (CPX) and transthoracic echocardiograms to understand the mechanism(s) of reduced exercise capacity across body mass index groups. Over a 6-year period, 510 consecutive patients with HC seen at a tertiary referral center underwent (CPX) and a transthoracic echocardiogram. Increasing BMI was associated with decreased exercise capacity as assessed by peak VO2 (ml/kg/min). However, the prevalence of cardiac impairment did not vary by BMI group. In conclusion, these findings suggest that in some patients with hypertrophic cardiomyopathy, cardiac impairment is not the primary cause of exercise limitation and weight loss may result in improved exercise capacity.

Women with hypertrophic cardiomyopathy have worse survival.

AIMS: Sex differences in hypertrophic cardiomyopathy (HCM) remain unclear. We sought to characterize sex differences in a large HCM referral centre population. METHODS AND RESULTS: Three thousand six hundred and seventy-three adult patients with HCM underwent evaluation between January 1975 and September 2012 with 1661 (45.2%) female. Kaplan-Meier survival curves were assessed via log-rank test. Cox proportional hazard regression analyses evaluated the relation of sex with survival. At index visit, women were older (59 ± 16 vs. 52 ± 15 years, P < 0.0001) had more symptoms [New York Heart Association (NYHA) Class III-IV 45.0% vs. 35.3%, P < 0.0001], more obstructive physiology (77.4% vs. 71.8%, P = 0.0001), more mitral regurgitation (moderate or greater in 56.1% vs. 43.9%, P < 0.0001), higher E/e' ratio (n = 1649, 20.6 vs. 15.6, P < 0.0001), higher estimated pulmonary artery systolic pressure (n = 1783, 40.8 ± 15.4 vs. 34.8 ± 10.8 mmHg, P < 0.0001), worse cardiopulmonary exercise performance (n = 1267; percent VO2 predicted 62.8 ± 20% vs. 65.8 ± 19.2%, P = 0.007), and underwent more frequent alcohol septal ablation (4.9% vs. 3.0%, P = 0.004) but similar frequency of myectomy (28% vs. 30%, P = 0.24). Median follow-up was 10.9 (IQR 7.4-16.2) years. Kaplan-Meier analysis demonstrated lower survival in women compared with men (P < 0.0001). In multivariable modelling, female sex remained independently associated with mortality (HR 1.13 [1.03-1.22], P = 0.01) when adjusted for age, NYHA Class III-IV symptoms, and cardiovascular comorbidities. CONCLUSION: Women with HCM present at more advanced age, with more symptoms, worse cardiopulmonary exercise tolerance, and different haemodynamics than men. Sex is an important determinant in HCM management as women with HCM have worse survival. Women may require more aggressive diagnostic and therapeutic approaches.

Inpatient Mortality Risk Scores and Postdischarge Events in Hospitalized Heart Failure Patients: A Community-Based Study.

BACKGROUND: The Acute Decompensated Heart Failure National Registry (ADHERE) and Get With The Guidelines (GWTG) registries have developed simple heart failure (HF) in-hospital mortality risk scores. We hypothesized that HF scores predictive of in-hospital mortality would perform as well for early postdischarge mortality risk stratification. METHODS AND RESULTS: In this single-center, community-based, retrospective study of all consecutive primary HF hospitalizations (6203 hospitalizations in 3745 patients) from 2000 to 2013, the ADHERE and GWTG risk scores were calculated from admission data. There were 176 (3.0%) and 399 (6.7%), 869 (14.7%), and 1272 (21.5%) deaths in-hospital and at 30, 90, and 180 days postdischarge, respectively. The GWTG but not ADHERE risk score was well calibrated for in-hospital mortality. Both the ADHERE (C statistic 0.66 and 0.67, 0.64, and 0.64) and GWTG (C statistic 0.74 and 0.73, 0.71, and 0.70) HF risk scores were similarly predictive of in-hospital and 30-, 90-, and 180-day postdischarge mortality. The ADHERE risk score identified 10% and the GWTG risk score identified 20% of hospitalizations where 180-day postdischarge mortality was 50%, a prognostic bench mark for hospice referral. In contrast, hospitalizations characterized as lowest risk by the ADHERE (57% of hospitalizations; 180-day mortality 16.2%) or GWTG score (20% of hospitalizations; 180-day mortality 8.0%) had substantially lower mortality (odds ratios high versus low risk of 5-8 [ADHERE] and 11-18 [GWTG] across time points; P<0.0001 for all). CONCLUSIONS: The simple ADHERE and GWTG scores stratify hospitalized HF patients for both inpatient and early postdischarge mortality risk, allowing comprehensive risk assessment on admission.

The Natural History of Nonobstructive Hypertrophic Cardiomyopathy.

OBJECTIVE: To describe the survival of a large nonobstructive hypertrophic cardiomyopathy (NO-HCM) cohort and to identify risk factors for increased mortality in this population. PATIENTS AND METHODS: Patients were identified from the Mayo Clinic HCM database from January 1, 1975, through November 30, 2006, for this retrospective observational study. Patients with resting or provocable left ventricular outflow tract gradients were excluded. Echocardiographic, clinical, and genetic data were compared between subgroups, and survival data were compared with expected population rates. RESULTS: A total of 706 patients with NO-HCM were identified. During median follow-up of 5 years (mean, 7 years), there were 208 deaths. Overall survival was no different than expected compared with age- and sex-matched white US population mortality rates (P=.77). Independent predictors of death were age at diagnosis, "burned out" HCM, and history of transient ischemic attack or stroke; use of an implantable cardioverter defibrillator (ICD) was inversely related to death. After exclusion of patients with an ICD, there was no difference in survival compared with age- and sex- matched individuals (P=.39); age, previous transient ischemic attack/stroke, and burned out HCM were predictors of death. CONCLUSION: In this cohort, patients with NO-HCM had similar survival rates as age- and sex-matched white US population mortality rates. Although use of an ICD was inversely related to death, no differences in overall survival were seen after those patients were excluded. Burned out HCM was independently associated with an increased risk of death, identifying a subset of patients who may benefit from more aggressive therapies.

Pulmonary hypertension is associated with worse survival in hypertrophic cardiomyopathy.

AIMS: Pulmonary hypertension (PH) is associated with increased mortality in various forms of left-sided heart disease. However, the implications of PH in hypertrophic cardiomyopathy (HCM) have not been elucidated. The objective of this study was to determine the prevalence and prognostic implications of PH in HCM. METHODS AND RESULTS: The study cohort consisted of 1570 (54 ± 15 years; 53% male) adults with HCM followed for a median of 3.3 years. PH [pulmonary artery systolic pressure (PASP) >36 mmHg] was identified in 38% of patients who were older (57 ± 15 vs. 52 ± 15 years, P < 0.0001), more likely to be female (59 vs. 40%, P < 0.0001), and were characterized by a higher prevalence of New York Heart Association (NYHA) class 3 or 4 symptoms (61 vs. 45%, P < 0.0001) and atrial fibrillation (29 vs. 15%, P < 0.0001) vs. those without PH. Only 12% had moderate or severe PH (PASP >50 mmHg). In multivariate Cox regression analyses adjusted for age, sex, NYHA class 3 or 4 symptoms, and atrial fibrillation, PASP was an independent predictor of all-cause mortality in patients with non-obstructive HCM (HR 1.59 per 10 mmHg PASP increase, 95% CI 1.28-1.96, P < 0.0001) and in those with obstructive physiology who did not undergo septal reduction therapy (SRT) (HR 1.15 per 10 mmHg PASP, 95% CI 1.01-1.31, P = 0.035). However, PH was not predictive of outcomes in patients with obstructive HCM who underwent SRT. CONCLUSIONS: Over one-third of adults evaluated in our referral HCM clinic demonstrated concomitant PH, and this was associated with increased mortality except in those with obstructive HCM who underwent SRT.

Electrogram guidance: a method to increase the precision and diagnostic yield of endomyocardial biopsy for suspected cardiac sarcoidosis and myocarditis.

OBJECTIVES: The aim of this study was to describe the method used to perform electrogram-guided EMB and correlate electrogram characteristics with pathological and clinical outcomes. BACKGROUND: Endomyocardial biopsy (EMB) is valuable in determining the underlying etiology of a cardiomyopathy. The sensitivity, however, for focal disorders, such as lymphocytic myocarditis and cardiac sarcoidosis (CS), is low. The sensitivity of routine fluoroscopically guided EMB is low. Abnormal intracardiac electrograms are seen at sites of myocardial disease. However, the exact value of electrogram-guided EMB is unknown. METHODS: We report 11 patients who underwent electrogram-guided EMB for evaluation of myocarditis and CS. RESULTS: Of 40 total biopsy specimens taken from 11 patients, 19 had electrogram voltage <5 mV, all of which resulted in histopathologic abnormality (100% specificity and positive predictive value). A voltage amplitude cutoff value of 5 mV had substantially higher sensitivity (70% vs. 26%) and negative predictive value (62%) than 1.5 mV. Abnormal electrogram appearance at biopsy site had good sensitivity (67%) and specificity (92%) in predicting abnormal myocardium. Normal signals with voltage >5 mV signified normal myocardium with no significant diagnostic yield. Biopsy results guided therapy in all patients, including 5 with active myocarditis or CS, all of whom subsequently received immunosuppressive therapy. There were no procedural complications. CONCLUSIONS: In patients with suspected myocarditis or CS, electrogram-guided EMB targeting sites with abnormal or low-amplitude electrograms may increase the diagnostic yield for detecting abnormal pathological findings.

Left atrial anatomy and physiology: echo/Doppler assessment.

PURPOSE OF REVIEW: This article provides a state-of-the-art perspective of left atrial anatomy and physiology. RECENT FINDINGS: Left atrial structure and function can be used to reflect and quantify the physiologic state of complex disease processes. No single left atrial anatomic, functional, or clinical feature will adequately define a complex system. The state of combined left atrial structural and functional features (i.e., systems biology) defines disease clustering (i.e., commonality of underlying left atrial pathophysiology), cause and effect (i.e., left atrial dynamics impute disease events as consequences), disease classification (e.g., primary vs. secondary atrial fibrillation), and intensity of a pathophysiologic state (i.e., quantifiably infer the magnitude of a pathophysiologic perturbation), and helps explain complex pathophysiology (e.g., myocyte death vs. hibernation). SUMMARY: Individual left atrial structural and functional features do not define the state of complex systems. Systems biology and multifeature profiles of left atrial anatomy and physiology should be used to assist the prediction, management, and, ultimately, prevention of preclinical and overt complex disease processes.

Formin homology 2 domain containing 3 variants associated with hypertrophic cardiomyopathy.

BACKGROUND: Incomplete penetrance and variable expression of hypertrophic cardiomyopathy (HCM) is well appreciated. Common genetic polymorphisms variants that may affect HCM penetrance and expression have been predicted but are not well established. METHODS AND RESULTS: We performed a case-control genomewide association study to identify common HCM-associated genetic polymorphisms and then asked whether such common variants were more represented in HCM or could explain the heterogeneity of HCM phenotypes. We identified an intronic FHOD3 variant (rs516514) associated with HCM (odds ratio, 2.45; 95% confidence interval, 1.76-3.41; P=1.25×10(-7)) and validated this finding in an independent cohort. Next, we tested FHOD3-V1151I (rs2303510), a nonsynonymous variant in partial linkage disequilibrium with rs516514, and we detected an even stronger association with HCM (P=1.76×10(-9)). Although HCM patients were more likely to carry these, FHOD3 allele subjects homozygous for FHOD3-1151I had similar HCM phenotypes as carriers of the V1151 allele. FHOD3 expression is increased in the setting of HCM, and both alleles of FHOD3-V1151I were detected in HCM myectomy tissue. Previously, FHOD3 was found to be required for formation of the sarcomere, and here we demonstrate that its fly homolog fhos is required for normal adult heart systolic contraction. CONCLUSIONS: Here we demonstrate the association of a common nonsynonymous FHOD3 genetic variant with HCM. This discovery further strengthens the potential role of gene mutations and polymorphisms that alter the amino acid sequence of sarcomere proteins and HCM.