Recreational and occupational physical activity and risk of adverse events in truncatingMYBPC3founder variant carriers

Background MYBPC3 founder variants cause hypertrophic cardiomyopathy (HCM) leading to heart failure (HF) and malignant ventricular arrhythmias (MVA). Exercise is typically regarded a risk factor for disease expression, although evidence is conflicting. Stratifying by type of exercise may discriminate low-from high-risk activities in these patients. Objective(s) Evaluate effects of exercise, stratified by high-static and high-dynamic component, on risk of major cardiomyopathy-related events (MCE) and cardiomyopathy penetrance among MYBPC3 founder variant carriers. Methods We interviewed 188 carriers (57% male, 43.4±14.8 years) on exercise participation since age ten. Exercise was quantified as metabolic equivalent task (MET)-hours/week before presentation. MCE was defined as a composite of MVA (sustained ventricular tachycardia/fibrillation), HF (HF hospitalizations or transplantation), and septal reduction therapy. Static and dynamic exercise were defined per Bethesda classification. Associations of exercise with MCE and cardiomyopathy penetrance were adjusted for sex and assessed using Cox regression. Results Overall, 40 (21%) subjects experienced MCE and 139 (74%) were diagnosed with cardiomyopathy. No association was found for overall physical activity and high-static activity with MCE (p=0.900 overall; p=0.274 high-static) or cardiomyopathy penetrance (p=0.787 overall; p=0.774 high-static). In contrast, high-dynamic activity was associated with MVA (dichotomized at 75 th percentile: adjusted hazard ratio 2.70, 95% confidence interval 1.01-7.24, p=0.049). Conclusions Overall exercise participation does not generally increase the risk of adverse events among MYBPC3 founder variant carriers. Nonetheless, an increased risk of MVA was observed among those engaged in the highest quartile of high-dynamic-sports, suggesting that high-level high-intensity exercise activities should be entertained with caution.