Abstract
Although maximal oxygen consumption (MVO2) is useful in predicting prognosis and need for cardiac transplantation (TX) in patients with advanced heart failure (HF), its determination requires sophisticated equipment. The six-minute walk test (6-MW) is a simple indirect measure of functional capacity, and predicts survival in moderate HF To assess the predictive value of the 6-MW, MVO2, and percent predicted age-sex adjusted MVO2 (%MVO2) in advanced HF, 45 pts (age 49±8 yrs mean±SD, LVEF 0.20±0.06, RVEF 0.31±0.11) underwent cardiopulmonary exercise testing (cycle ergometry) and the 6-MW during TX evaluation. Mean 6-MW distance ambulated was 310±100 meters, MV02 12.2±4.5ml/kg/min, and %MVO2 38±11%. Multivariate analysis of patient characteristics, resting hemodynamics and 6-MW (age, sex, weight, peak HR and BP during the 6-MW, right and left ventricular ejection fraction, right atrial pressure, mean pulmonary artery pressure, and cardiac index) identified distance ambulated during the 6-MW as the strongest predictor of MVO2 (p<0.000) and %MVO2 (p<0.000). In univariate survival analysis, 6-MW>300 meters predicted survival to the combined end-point death or hospital admission for inotropic/mechanical support (IN) as a bridge to TX (p<0.05). but not overall survival (p=0.075). In multivariate proportional hazards survival analysis designed to compare %MVO2, MVO2, and 6-MW, MVO2 was selected as the best predictor of overall survival, and %MVO2 as the best predictor of IN-free survival. 6-MW was not selected in any multivariate analysis.
In pts with advanced HF evaluated for TX, distance ambulated during the 6-MW predicts 1) MVO2 and %MVO2 and 2) IN-free survival but not overall survival. MVO2 and %MVO2 may be superior to the 6-MW as predictors of survival in these pts: however, further studies to es1ablish the prognostic utility of the 6-MW in pts with advanced HF are warranted.