Objective: To assess the intensity and daily reliability of the six-minute walk test (6MWT) in patients with moderate chronic heart failure (CHF).
Design: Evaluation of testing protocol.
Setting: Hospitalized care.
Participants: CHF patients under optimal drug treatment (CHF-D, n=12) or optimal drug treatment plus multisite cardiac pacing (CHF-P, n=12).
Interventions: Not applicable.
Main outcome measures: Peak values of oxygen uptake (VO2) and heart rate during a symptom-limited, treadmill exercise test and VO2, heart rate, and distance during 2 6MWT sessions (morning and afternoon). The 6MWT intensity was estimated by the ratio (%) of VO2 and heart rate values measured at the end of this test in relation to the respective peak values obtained during the treadmill exercise test.
Results: Subjects' VO2 and heart rate during the 6MWT were lower (P<.001) and were about 90% of the peak values (VO2: CHF-D, 90.5%+/-11.1%; CHF-P, 93.0%+/-13.2%; heart rate: CHF-D, 90.6%+/-6.6%; CHF-P, 91.4%+/-9.6%). The distance walked during both 6MWT sessions did not differ significantly, with low coefficients of variation (< or =2.0%) and high intraclass correlation coefficients (> or =.98). In CHF-D only, the patients' VO2 and heart rate were significantly (P<.01, P<.05, respectively) higher during the afternoon session.
Conclusions: Despite an intensity significantly lower but close to that of the symptom-limited exercise test, the 6MWT was well tolerated in both CHF groups. In these populations, the 6MWT is reliable on a daily basis, for the distance walked. However, for assessing VO2 and heart rate values in CHF-D patients, the 6MWT must always be performed at the same time of day.