(P096) ASSOCIATION OF DURATION AND INTENSITY OF EXERCISE WITH SEVERITY OF PHENOTYPIC EXPRESSION IN HYPERTROPHIC CARDIOMYOPATHY

Background: Hypertrophic Cardiomyopathy (HCM) is an inherited cardiomyopathy with incomplete penetrance and variable phenotypic expression. The factors influencing the severity of phenotypic expression remain unknown. HCM is an important cause of sudden cardiac death in athletes. However, exercise can potentially lead to significant, but reversible, left ventricular hypertrophy in patients without HCM (i.e. the “athletes heart”). Exercise restriction however, may lead to decreased quality of life, and increased traditional cardiac disease risk factors including hypertension and diabetes. In this study we aimed to assess the association between exercise duration and intensity and the severity of phenotypic expression in genotype positive HCM patients

METHODS AND RESULTS: Participants with a confirmed pathogenic genetic variant were recruited through the HCM clinic at Toronto General Hospital. Patients were asked to answer a structured phone questionnaire regarding routine physical activity since the age of 10. Metabolic equivalent (MET) hours were calculated using standardized estimates based on activity type. Endurance training was defined as dynamic exercise estimated to be at an intensity of >70% of maximal oxygen consumption. Echocardiographic, cardiac magnetic resonance (CMR), and outcome data, including septal reduction interventions and atrial fibrillation, was retrospectively collected from patient charts. A total of 109 participants (43 male, 66 female) from 55 families were recruited. In those that were phenotype positive (90/109), average age at diagnosis was 35.6 (+/- 16.7), with an average maximal wall thickness of 17.8mm (+/- 4.9), and average late-gadolinium-enhancement (LGE) percentage of 7.0% (+/- 8.9%) in the 61 that had had CMR. No association was identified between average MET-hours per year of exercise or duration of endurance training and markers of phenotype severity including age at diagnosis, left atrial diameter, maximal wall thickness, LV mass or LGE percentage. Similarly, no difference in these parameters was demonstrated when participants were stratified by not meeting, meeting, or exceeding AHA guideline recommendations for exercise. This was true for exercise done up to the age of 20, up to the age of 30, or up to the time of follow-up (Table 1). Within family clusters, there were no examples of exercise associated with disease outcomes (Figure 1).

Conclusion: In this retrospective study of gene-positive HCM patients, we found no association between exercise intensity and duration and severity of HCM phenotypic expression. These findings are important for physician-patient discussions and support the recent trend towards more permissive exercise restrictions in HCM.