Ho, Carolyn Y.

Importance Current risk prediction guidelines for hypertrophic cardiomyopathy predict only sudden cardiac death and are imperfect, leading to avoidable deaths and unnecessary implantable cardioverter defibrillators. Objective To combine prospectively collected clinical history, imaging, genetic, and biomarker data to improve risk prediction of adverse events in hypertrophic cardiomyopathy. Design, Setting, and Participants A total of 2750 patients with hypertrophic cardiomyopathy were prospectively enrolled in the registry-based study from 44 sites in North America and Europe with expertise in hypertrophic cardiomyopathy and cardiac magnetic resonance (CMR) imaging. Participants were enrolled from April 1, 2014, to April 7, 2017. Exposures Patients underwent a health history questionnaire, blood sampling for biomarkers and genotyping, and contrast-enhanced CMR. Patients were followed up yearly by telephone and through records review regarding event documentation. Main Outcomes and Measures The predefined composite adjudicated primary end point was time to first event for hypertrophic cardiomyopathy–related deaths; nonfatal sustained ventricular arrhythmias (VAs) requiring cardioversion or defibrillation; and left ventricular (LV) assist device implant or heart transplant. A secondary end point was a composite of sudden cardiac death and nonfatal VA events. The elastic-net method identified the most important predictors. Cox proportional hazards regression assessed associations with time to the first end point. Results Of the 2750 prospectively enrolled patients, 2698 (98%) had analyzable data after 9 were excluded because they had hypertrophic cardiomyopathy phenocopies and 43 withdrew. Of these remaining patients, 1919 (71%) were male, mean age was 50 years (SD, 11 years), and 423 (16%) were from underrepresented racial and minority groups. The mean follow-up was 6.9 years (SD, 2.1 years). The primary event model in 104 patients included LV scar as a percentage of LV mass by late gadolinium enhancement (LGE%; hazard ratio [HR], 1.86; 95% CI, 1.58-2.20; P < .001), LV mass index (HR, 1.09; 95% CI, 1.01-1.17; P = .03), LV end-systolic volume index (HR, 1.28; 95% CI, 1.12-1.46; P < .001 ), all per 10-unit increase, history of heart failure at study entry (HR, 2.89; 95% CI, 1.75-4.77; P < .001), and log N-terminal pro–B-type natriuretic peptide (NT-proBNP; HR, 1.41; 95% CI, 1.17-1.70; P < .001) level per log unit, (C index for all, 0.77). An LGE percentage of the LV mass of 9% or higher substantially increased the primary composite event rate ( P = .001). The secondary sudden cardiac death and VA risk factor model (in 69 patients) included LGE%, LV mass index, LV ejection fraction, and log(NT-proBNP) (C index, 0.76). Conclusions and Relevance These results provide prospective evidence for incorporating cardiac magnetic resonance and NT-proBNP in the evaluation of patients with hypertrophic cardiomyopathy. Trial Registration ClinicalTrials.gov Identifier: NCT01915615

Abstract Background and Aims Truncating variants in the TTN gene (TTNtv) are the most common genetic cause of dilated cardiomyopathy (DCM) but also occur as incidental findings in the general population. This study investigated factors associated with the clinical manifestation of TTNtv. Methods An international multicentre retrospective observational study was performed in families with TTNtv-related DCM. Shared frailty models were used to estimate associations of variant characteristics with lifetime risk of DCM, and logistic regression to estimate odds ratios (ORs) for individual-level clinical risk factor profiles (cardiac conditions, cardiovascular comorbidities, lifestyle) and DCM. Results A total of 3158 subjects in 1043 families with TTNtv-related DCM were studied. TTNtv-positive subjects were 21-fold more likely to develop DCM [OR, 21.21; 95% confidence interval (CI), 14.80–30.39]. Disease onset was earlier in males, but was similar for TTNtv of different types and locations. The presence of clinical risk factors was associated with earlier DCM onset (OR, 3.41; 95% CI, 2.06–5.64), with a prior history of atrial fibrillation having a two-fold increased odds of DCM (OR, 2.05; 95% CI, 1.27–3.32). The prevalence of clinical risk factors increased with age; however, the strength of the DCM association was greatest for young-onset (<30 years) disease (OR, 4.75; 95% CI, 2.35–9.60). Administration of beta-adrenergic receptor or renin-angiotensin system-blocking drugs prior to overt DCM was associated with 87% reduced odds of DCM (OR, .13; 95% CI, .08–.23). Conclusions Disease onset in TTNtv-associated familial DCM is dependent on individual patient context and is potentially modifiable by risk factor management and prophylactic therapeutic intervention.

Importance Whether vigorous intensity exercise is associated with an increase in risk of ventricular arrhythmias in individuals with hypertrophic cardiomyopathy (HCM) is unknown. Objective To determine whether engagement in vigorous exercise is associated with increased risk for ventricular arrhythmias and/or mortality in individuals with HCM. The a priori hypothesis was that participants engaging in vigorous activity were not more likely to have an arrhythmic event or die than those who reported nonvigorous activity. Design, Setting, and Participants This was an investigator-initiated, prospective cohort study. Participants were enrolled from May 18, 2015, to April 25, 2019, with completion in February 28, 2022. Participants were categorized according to self-reported levels of physical activity: sedentary, moderate, or vigorous-intensity exercise. This was a multicenter, observational registry with recruitment at 42 high-volume HCM centers in the US and internationally; patients could also self-enroll through the central site. Individuals aged 8 to 60 years diagnosed with HCM or genotype positive without left ventricular hypertrophy (phenotype negative) without conditions precluding exercise were enrolled. Exposures Amount and intensity of physical activity. Main Outcomes and Measures The primary prespecified composite end point included death, resuscitated sudden cardiac arrest, arrhythmic syncope, and appropriate shock from an implantable cardioverter defibrillator. All outcome events were adjudicated by an events committee blinded to the patient’s exercise category. Results Among the 1660 total participants (mean [SD] age, 39 [15] years; 996 male [60%]), 252 (15%) were classified as sedentary, and 709 (43%) participated in moderate exercise. Among the 699 individuals (42%) who participated in vigorous-intensity exercise, 259 (37%) participated competitively. A total of 77 individuals (4.6%) reached the composite end point. These individuals included 44 (4.6%) of those classified as nonvigorous and 33 (4.7%) of those classified as vigorous, with corresponding rates of 15.3 and 15.9 per 1000 person-years, respectively. In multivariate Cox regression analysis of the primary composite end point, individuals engaging in vigorous exercise did not experience a higher rate of events compared with the nonvigorous group with an adjusted hazard ratio of 1.01. The upper 95% 1-sided confidence level was 1.48, which was below the prespecified boundary of 1.5 for noninferiority. Conclusions and Relevance Results of this cohort study suggest that among individuals with HCM or those who are genotype positive/phenotype negative and are treated in experienced centers, those exercising vigorously did not experience a higher rate of death or life-threatening arrhythmias than those exercising moderately or those who were sedentary. These data may inform discussion between the patient and their expert clinician around exercise participation.

Introduction: Safety of vigorous exercise for individuals with appropriately-treated HCM remains debated. Physical activity practices in this population have not been described. The objective of this report is to describe physical activity pattern in HCM patients. Long term follow up which is ongoing will determine safety of vigorous exercise. Methods: The NIH-funded LIVE-HCM study prospectively enrolled individuals age 8-60 years with clinically overt HCM or patients with a positive genetic test for sarcomeric HCM. Participants (or parents, for children) answered surveys describing activity patterns. Vigorous exercise was defined as > 6 METS for > 60 hours per year. Clinical and demographic data were derived from medical record review. Results: Among 1798 participants, 745 (41%) reported exercising vigorously, including 296 competitive athletes, with 59 at high-school or college varsity level, 770 (43%) were exercising at moderate, and 283 (16%) at low levels. Of those working, 6% described jobs more active than walking, including 16 in protective services, and 11 in sports/coaching. Clinical/demographic data including imaging characteristics and treatments, are shown in Table, and were mostly similar amongst the exercise-groups. Conclusions: Many patients with HCM are engaged in vigorous exercise including competitive athletics. Prospective follow-up of this cohort is ongoing. Comparison of arrhythmic outcomes outcomes in vigorous exercisers vs moderate/low level exercisers will help determine the safety of exercise in HCM patients.

Introduction: Hypertrophic cardiomyopathy (HCM) carries substantial lifelong morbidity. Mutations in sarcomeric proteins that lead to HCM cause excess contractility, poor relaxation, and inefficient energy utilization. Although obstructive physiology is a prominent feature of disease, approximately 30% of HCM patients experience symptoms in the context of non-obstructive HCM (nHCM). Management options are extremely limited with little other than cardiac transplantation to offer severely affected patients. Mavacamten (MAVA), a first-in-class small molecule, is a selective modulator of cardiac myosin that inhibits the cardiac myosin ATPase to reversibly attenuate cardiac contractility. In addition to its effects on contractility, MAVA has been shown to improve LV compliance in preclinical and clinical studies. The Phase 2 MAVERICK-HCM study is designed to evaluate safety and tolerability, and to provide pilot data on the effects of MAVA on biomarkers, cardiac function, and exercise capacity in nHCM. Methods: This double-blind study will enroll 60 individuals with nHCM (Left ventricular outflow tract gradient <30 mmHg; resting or provoked), NYHA Class II or III, and LVEF ≥55%. Subjects will be randomized 1:1:1 to one of two target plasma drug concentrations (Group 1: ~200 ng/mL and Group 2: ~500 ng/mL) or placebo for 16 weeks. The starting dose of MAVA is 5 mg, with one-step dose titration at Week 6 based on plasma drug concentration. Predefined criteria, including LVEF, will guide study drug discontinuation if indicated. Cardiopulmonary exercise testing will be performed at baseline and Week 16 to assess the impact on exercise capacity. The primary endpoint is the frequency and severity of treatment-emergent adverse events. The study design also includes multiple secondary endpoints including echocardiographic measures of diastolic function, NT-proBNP levels, patient reported outcomes, and physical activity by wearable accelerometer. An independent data monitoring committee will oversee safety. Conclusions: MAVERICK-HCM is testing a novel therapy to improve symptom burden in nHCM; a patient cohort currently lacking effective treatment. By targeting a core molecular mechanism of disease, MAVA has the potential to alter natural history.

Introduction: Obstructive hypertrophic cardiomyopathy (oHCM) is characterized by dynamic LV outflow tract (LVOT) obstruction resulting from ventricular hypertrophy and mitral valve systolic anterior motion (SAM), and by elevated left ventricular (LV) filling pressures, all of which result in a significant morbidity despite medical therapy. Mavacamten (Mava) is a novel inhibitor of cardiac myosin that significantly reduces LVOT gradients in oHCM, noted initially in the phase 2 PIONEER and more recently in the phase 3 EXPLORER-HCM studies. Additional echocardiographic analyses were performed to investigate the effect of Mava on focused measures of cardiac structure and function in oHCM. Methods: EXPLORER-HCM (NCT03470545) was a multicenter, double-blind, placebo-controlled, phase 3 study that randomized symptomatic oHCM patients (LV ejection fraction ≥55% and resting and/or provoked LVOT gradient ≥50 mmHg) 1:1 to Mava vs placebo for 30 weeks. Echocardiograms were performed serially every 2-4 weeks over 30 weeks. Results: In total, 251 patients with oHCM were enrolled and 244 patients completed the study (mean age 58.5; 40.6% female). Compared to placebo, 30-week treatment with Mava led to significant reductions in LA volume index (-7.5 ml/m 2 , p<0.0001), lateral E/e’ (-3.8, p<0.0001), septal E/e’ (-3.4, p<0.0001), and LV mass index (-15.5 g/m 2 , p<0.0001) ( Table ). Significantly more Mava-treated patients achieved resolution of mitral valve SAM compared to placebo (80.9% vs 34.0% of patients; difference of 46.8%; p<0.0001) and mitral regurgitation (MR) (9.0% vs 0.0% of patients; difference of 9.0%; p=0.0006). Conclusions: Treatment with Mava for 30 weeks led to improvement in LV hypertrophy and markers of left-sided filling pressures (LA volume and E/e’). Furthermore, Mava treatment was associated with reduction of SAM and MR. These findings suggest that Mava has beneficial effects on several adverse pathophysiologic processes that are hallmarks of oHCM.

Background: Obstructive hypertrophic cardiomyopathy (oHCM) is characterized by unexplained left ventricular (LV) hypertrophy associated with dynamic LV outflow tract obstruction. Current medical therapies are nonspecific and have limited efficacy in relieving symptoms. Mavacamten is a first-in-class targeted inhibitor of cardiac myosin, which has been shown to reduce LV outflow tract obstruction, improve exercise capacity, and relieve symptoms of oHCM in the PIONEER-HCM phase 2 study. Methods: EXPLORER-HCM is a multicenter, phase 3, randomized, double-blind, placebo-controlled trial to investigate the efficacy and safety of mavacamten in treating symptomatic oHCM. Eligible adults with oHCM and New York Heart Association Functional Class II or III are randomized 1:1 to receive once-daily, oral mavacamten, or matching placebo for 30 weeks. The primary composite functional end point is clinical response at week 30 compared to baseline defined as either (1) an increase in peak oxygen consumption ≥1.5 mL/kg/min and reduction of at least one New York Heart Association class; or (2) an improvement of ≥3.0 mL/kg/min in peak oxygen consumption with no worsening of New York Heart Association class. Secondary end points include change in postexercise LV outflow tract gradient, New York Heart Association class, peak oxygen consumption, and patient-reported outcomes assessed by the Kansas City Cardiomyopathy Questionnaire and a novel HCM-specific instrument. Exploratory end points aim to characterize the effect of mavacamten on multiple aspects of oHCM pathophysiology. Conclusions: EXPLORER-HCM is a phase 3 trial in oHCM testing a first-in-class, targeted strategy of myosin inhibition to improve symptom burden and exercise capacity through reducing LV outflow tract obstruction. Results of this trial will provide evidence to support the first disease-specific treatment for HCM. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03470545.