Importance: Mavacamten, a cardiac myosin inhibitor, improved peak oxygen uptake (pVO2) in patients with symptomatic obstructive hypertrophic cardiomyopathy (HCM) in the EXPLORER-HCM study. However, the full extent of mavacamten's effects on exercise performance remains unclear.Objective: To investigate the effect of mavacamten on exercise physiology using cardiopulmonary exercise testing (CPET).Design, Setting, and Participants: Exploratory analyses of the data from the EXPLORER-HCM study, a randomized, double-blind, placebo-controlled, phase 3 trial that was conducted in 68 cardiovascular centers in 13 countries. In total, 251 patients with symptomatic obstructive HCM were enrolled.Interventions: Patients were randomly assigned in a 1:1 ratio to mavacamten or placebo.Main Outcomes and Measures: The following prespecified exploratory cardiovascular and performance parameters were assessed with a standardized treadmill or bicycle ergometer test protocol at baseline and week 30: carbon dioxide output (VCO2), minute ventilation (VE), peak VE/VCO2 ratio, ventilatory efficiency (VE/VCO2 slope), peak respiratory exchange ratio (RER), peak circulatory power, ventilatory power, ventilatory threshold, peak metabolic equivalents (METs), peak exercise time, partial pressure of end-tidal carbon dioxide (PETCO2), and VO2/workload slope.Results: Two hundred fifty-one patients were enrolled. The mean (SD) age was 58.5 (11.9) years and 59% of patients were male. There were significant improvements with mavacamten vs placebo in the following peak-exercise CPET parameters: peak VE/VCO2 ratio (least squares [LS] mean difference, -2.2; 95% CI, -3.05 to -1.26; P<.001), peak METs (LS mean difference, 0.4; 95% CI, 0.17-0.60; P<.001), peak circulatory power (LS mean difference, 372.9 mL/kg/min*mm Hg; 95% CI, 153.12-592.61; P=.001), and peak PETCO2 (LS mean difference, 2.0 mm Hg; 95% CI, 1.12-2.79; P<.001). Mavacamten also improved peak exercise time compared with placebo (LS mean difference, 0.7 minutes; 95% CI, 0.13-1.24; P = .02). There was a significant improvement in nonpeak-exercise CPET parameters, such as VE/VCO2 slope (LS mean difference, -2.6; 95% CI, -3.58 to -1.52; P<.001) and ventilatory power (LS mean difference, 0.6 mm Hg; 95% CI, 0.29-0.90; P<.001) favoring mavacamten vs placebo.Conclusions and Relevance: Mavacamten improved a range of CPET parameters beyond pVO2, indicating consistent and broad benefits on maximal exercise capacity. Although improvements in peak-exercise CPET parameters are clinically meaningful, the favorable effects of mavacamten on submaximal exertional tolerance provide further insights into the beneficial impact of mavacamten in patients with obstructive HCM.Trial Registration: ClinicalTrials.gov Identifier: NCT03470545.
View details for DOI 10.1001/jamacardio.2022.5099
View details for PubMedID 36652223