Abstract 3351: Poor Metabolic Exercise Capacity Identifies Minimally Symptomatic Patients With Obstructive Hypertrophic Cardiomyopathy Who Are at Increased Risk of Death and Severe Heart Failure
Background. Patients with obstructive hypertrophic cardiomyopathy (HCM) and minimal symptoms may later develop refractory heart failure, leading to either severe morbidity or need for septal reduction therapy. This study investigated the utility of metabolic exercise testing for identifying mildly symptomatic or asymptomatic patients with obstructive HCM who are at such heightened risk.
Methods. We examined 182 patients at Mayo Clinic (mean age, 53±15 yrs; 65% men) with obstructive HCM (gradient ≥30 mmHg at rest and/or ≥50 mmHg with provocation) and minimal or no cardiovascular symptoms (Canadian Cardiac Society angina class I or II and NYHA functional class I or II). Each patient underwent maximal treadmill metabolic exercise testing with measurement of peak oxygen consumption (VO2), which was expressed as percentage of predicted by age, gender, and anthropometry (%VO2). Follow-up was performed to determine vital status and occurrence of severe symptoms, which was defined as class III/IV dyspnea or angina.
Results. Over a mean follow-up of 4.0±3.0 yrs, low %VO2 was associated with poor survival free of all-cause mortality and development of severe symptoms (Figure⇓). In multivariate analyses, the only predictors of death and severe symptoms were the severity of the resting LVOT gradient (RR, 1.01, 95%CI, 1.00 to 1.01;p=0.01) and %VO2 (RR, 0.98; 95% CI, 0.97 to 0.99;p=0.001).
Conclusion. In minimally symptomatic patients with obstructive HCM, reduced peak %VO2 identifies those at increased risk of death and heart failure.