The 6-min walk and peak oxygen consumption in advanced heart failure: Aerobic capacity and survival

Background This study sought to determine to what extent the 6-min walk (6M W) distance in advanced heart failure predicts aerobic capacity and provide s comparable information regarding survival. Peak oxygen uptake (VO2) and t he 6MW both describe function and predict outcome over a wide range of hear t failure, but their determinants and implications may differ within a narr ower clinical spectrum. This study compared 6MW with aerobic capacity both at peak exercise and during low-level cycling. Methods and Results Both the 6MW and symptom-limited cycle ergometry were p erformed by 307 patients of whom 264 patients additionally performed 6 min of 20-W cycling to estimate aerobic capacity during sustained low-level act ivity. In the first 198 patients, multivariate analysis of survival was per formed with the 6MW and peakVO(2). Patients achieved the 6MW of 393 +/- 104 m and peakVO(2) of 14 +/- 5 mL/kg per minute. Although low peak VO2 was mo re likely with the shorter 6MW, the relation was weak within peakVO(2) rang e of 10 to 20 mL/kg per minute (n = 213, 69% of patients, r = 0.28). During 20-W exercise, VO2 was 9.2 +/- 2.0 mL/kg per minute, with respiratory exch ange ratio poorly correlated with the 6MW. in contrast to peakVO(2), the 6M W in meters did not predict survival. Division into short, medium, and long walks, however, supplemented simple clinical description. Conclusions Although helpful in broader populations for identification of p atients with obvious clinical compromise, the 6MW distance is not a surroga te for peak VO2 in assessing aerobic capacity or prognosis for individuals with advanced heart failure.