Peak oxygen intake and cardiac mortality in women referred for cardiac rehabilitation

Objectives This study investigated the prognostic importance of measured peak oxygen intake (V̇O2peak) in women with known coronary heart disease referred for outpatient cardiac rehabilitation. Background Exercise capacity is a powerful predictor of prognosis in men with known or suspected coronary disease. Similar findings are described in women, but fewer studies have utilized measured V̇O2peak, the most accurate measure of exercise capacity. Methods A single-center design took data from 2,380 women, age 59.7 ± 9.5 years (1,052 myocardial infarctions, 620 coronary bypass procedures, and 708 with proven ischemic heart disease), who underwent cardiorespiratory exercise testing. They were followed for an average of 6.1 ± 5 years (median 4.5 years, range 0.4 to 25 years) until cardiac and all-cause death. Results We recorded 95 cardiac deaths and 209 all-cause deaths. Measured V̇O2peak was an independent predictor of risk, values ≥13 ml/kg/min (3.7 multiples of resting metabolic rate) conferring a 50% reduction in cardiac mortality (hazard ratio [HR] 0.5, p = 0.001). Considered as a continuous variable, a 1 ml/kg/min advantage in initial V̇O2peak was associated with a 10% lower cardiac mortality. Adverse predictors were diabetes (HR 2.73, p = 0.0005) and antiarrhythmic therapy (HR 3.93, p = 0.0001). Conclusions As in men, measured V̇O2peak is a strong independent predictor of cardiac mortality in women referred for cardiac rehabilitation.