Clinical phenotype and outcomes of low-risk HCM patients who maintained stable exercise habits during follow-up

Background: Patients with hypertrophic cardiomyopathy able to maintain regular exercise over time may represent a selected subgroup with a more favourable clinical phenotype. However, the clinical, morphological, and arrhythmic profile of low-risk HCM patients engaged in regular exercise programs over follow-up remains incompletely characterized. This study aimed to compare the phenotype and follow-up outcomes of low-risk HCM patients according to reliably documented and stable exercise habits during follow-up. Methods: 253 low-risk HCM were classified by their reported habitual physical activity into three groups: sedentary (n = 93), mild exercise (<30 METs/week, n = 117), and vigorous exercise (>30 METs/week, n = 43). Clinical data, ECGs, echocardiography, CMR, and Holter monitoring were compared. Mean follow-up from initial diagnosis was 3.5 ± 2.7 years. Results: Physically active patients showed significantly lower BMI (24.2 ± 3.8 and 24.8 ± 3.2 kg/m2 in vigorous and mild exercise, respectively, vs. 26.6 ± 4.3 kg/m2 in sedentary p = 0.004); lower max LV wall thickness (15.9 ± 2.9 and 17.5 ± 3.9 mm vs. 18.9 ± 3.9 mm; p < 0.0001) and better diastolic function (p < 0.0001). On CMR, late gadolinium enhancement was less prevalent in physically active patients (p < 0.0002). Active patients also showed fewer symptoms (p < 0.0001). Finally, no differences in arrhythmic burden or adverse events were observed among groups in the follow-up. Conclusions: In a low-risk HCM patients with stable exercise habits during follow-up, those participating in vigorous exercise programs showed a milder phenotype and did not experience excess arrhythmic burden or adverse cardiovascular events over time compared to sedentary HCM patients.