Functional capacity in patients with congestive heart failure

Background: Six-minute walk distance (6MWd) is related to activities of daily living and is also an independent predictor of prognosis in patients with congestive heart failure (CHF). Therefore. it is important to determine factors that contribute to the variability of this test. Methods and Results: We assessed the relationship between 6MWd and peak aerobic capacity (Vo(2)) and dynamic muscle strength in 180 patients with CHF (age, 66 +/- 10 years; 146 men, 34 women; ejection fraction, .29 +/- 0.08). We also hypothesized that a measure of work performed during the walk test (6MWw) would be a better indicator of exercise capacity than 6MWd. The 6MWd had weak to moderate correlations with dynamic muscle strength (r = 0.33 to 0.41) and peak Vo(2) (r = 0.48). However, 6MWw was strongly related to dynamic muscle strength (r = 0.63 to 0.70) and peak Vo(2) (r = 0.77). Multivariate analysis indicated that a model combining dynamic muscle strength and peak Vo(2) explained 69% of the variance in 6MWw, more than with peak Vo(2) alone (R-2 = 0.59). Conclusions: Compared with 6MWd, 6MMw correlates significantly better with peak iio, and dynamic muscle strength, suggesting that 6MMw may be a better reflection of a patient's exercise capacity. Further-more, these results suggest that an exercise program combining both aerobic and strength training in patients with CHF may improve 6MWw and therefore 6MWd.