Myocardial Contraction Fraction Predicts Cardiovascular Events in Patients With Hypertrophic Cardiomyopathy and Normal Ejection Fraction

Background: Myocardial contraction fraction (MCF), the ratio of left ventricular stroke volume to myocardial volume, is a novel parameter that can distinguish between pathologic and physiologic hypertrophy. However, its prognostic value in hypertrophic cardiomyopathy (HCM) has never been examined. The objective was to determine if MCF is associated with functional capacity and predicts adverse cardiovascular outcomes in patients with HCM and normal left ventricular ejection fraction (LVEF). Methods and Results: We conducted a prospective cohort study of 137 patients with HCM and LVEF >= 55%. Patients were followed for 2.7 +/- 2.5 years. We examined association of MCF with New York Heart Association (NYHA) functional class and a composite outcome of embolic stroke, heart transplantation, and cardiac death. We performed time-to-event analysis with the use of Cox proportional hazards modeling and stepwise elimination. The average age was 52 +/- 18 years. The average MCF was 26 +/- 11%. MCF was inversely correlated with NYHA functional class (P = .001). A total of 20 subjects experienced an outcome event with an event rate of 5.6% per patient-year. MCF independently predicted the outcome (adjusted hazard ratio 0.50 per 10% increase, 95% confidence interval 0.28-0.90, adjusted P = .02). Conclusions: In patients with HCM and normal LVEF, MCF is associated with functional capacity and independently predicts adverse cardiovascular outcomes.