Influence of step length on 6-minute walk test performance in patients with chronic heart failure

Abstract

ObjectiveTo investigate the influence of gait parameters including step length and walking speed during performance of the 6-minute walking test (6MWT) in patients with chronic heart failure (CHF). DesignObservational study. SettingSpecialist heart failure clinic. ParticipantsPatients with CHF and aged-matched, apparently healthy controls. InterventionsEach patient and control performed a 6MWT following a standardised protocol in a 15m corridor. The number of steps (defined as step from left foot to right foot) taken every 15m was counted, and reported as minute-by-minute changes in 6MWT performance. In addition, minute-by-minute changes in time taken to complete 15m and mean walking speed throughout the test were calculated. Main outcome measuresWalking speed and step length. ResultsThirty patients with CHF {87% males; mean age 75 [standard deviation (SD) 8] years} and 10 healthy controls [80% males; mean age 77 (SD 11) years] undertook the 6MWT. For the CHF group, the mean distance walked was 309 (SD 48)m and the peak Borg score was 12 (SD 1). For the controls, the mean distance walked was 334 (SD 138)m and the peak Borg score was 12 (SD 1). Patients with CHF showed no significant minute-by-minute changes in step length or walking speed over the course of the 6MWT. In the first 5minutes, healthy controls had a longer step length and faster walking speed than patients with CHF [step length: mean difference in the first minute was 0.03m, 95% confidence interval (CI) of the difference 0.01 to 0.05m; P=0.02; walking speed: mean difference in the first minute 0.04m/second, 95% CI of the difference 0.02 to 0.07m/second; P=0.01]. A multiple linear regression analysis demonstrated that body mass index (P=0.02) was the most important predictor of 6MWT performance. ConclusionPatients with CHF have a shorter step length and walk more slowly than controls during the 6MWT. Altered gait mechanics may contribute to limited exercise capacity in patients with CHF.