Abstract 19346: Peak Oxygen Consumption Predicts Outcome in Hypertrophic Cardiomyopathy

Introduction: Peak oxygen consumption (VO 2 ) has a strong and independent prognostic value in systolic heart failure; in contrast no data support its prognostic role in hypertrophic cardiomyopathy (HCM). Hypothesis: We assess if peak VO 2 is a long-term predictor of outcome in HCM. Methods: We studied 92 HCM patients (40±15 years). Peak VO 2 was expressed as percentage (%) of the predicted value. Follow up was 76±57 months. The primary composite endpoint (CE) was atrial fibrillation, progression to NYHA class III or IV, myotomy-myectomy (MM), heart transplantation (HT) and cardiac death. An ancillary endpoint (HFE) included markers of heart failure (progression to NYHA class III or IV, MM and HT). Results: At baseline, 62% of patients were asymptomatic, 35% NYHA class II and 3% NYHA class III; 26% had left ventricular outflow tract obstruction. During follow up, 30 patients met CE with 43 events. By multivariate Cox survival analysis, we analyzed 2 models, using the CE, and in turn HFE. For CE, maximal left atrial diameter (LAD) (HR: 1.12; 95% CI: 1.04 to 1.22), maximal wall thickness (MWT) (HR: 0.14; 95% CI: 1.04 to 1.23) and % predicted peak VO 2 (HR: -0.03; 95% CI: 0.95 to 0.99) independently predicted outcome (overall, p<0.0001). For HFE, maximal LAD (HR:0.31; 95% CI: 1.09 to 1.70), MWT (HR: 0.35; 95% CI: 1.08 to 1.84) and % predicted peak VO 2 (HR: -0.06; 95% CI: 0.89 to 0.98) independently predicted outcome (overall, p<0.0001). Only 19% of mildly symptomatic or asymptomatic patients with % predicted peak VO 2 >80% had events, as opposed to 53% of them with % predicted peak VO 2 < 55% (p= 0.04). Event-free survival for both endpoints was significantly lower in patients with % predicted peak VO 2 < 55% as compared to those with it between 55 and 80 and >80% , Figure. Conclusion: In mildly or asymptomatic patients severe exercise intolerance may precede clinical deterioration. In HCM, peak VO 2 provides excellent risk stratification with a high event rate in patients with % predicted value <55%.