Repeated six-minute walk tests for outcome measurement and exercise prescription in outpatient cardiac rehabilitation: a longitudinal study.

Objective: To determine whether repeated 6-minute walk tests (6MWTs) are required for outcome measurement and exercise prescription in a typical cardiac rehabilitation (CR) population.

Design: Prospective longitudinal observational study.

Setting: Outpatient community health center.

Participants: Sixty-one of 154 consecutive patients.

Intervention: 6MWTs (N = 2) were conducted at 3 assessment points: at CR start, postcompletion, and 6-months postcompletion.

Main Outcome Measure: 6MWT distance (6MWD).

Results: Mean 6MWD for the first (6MWT1) and second (6MWT2) 6MWTs at the 3 assessment points were 507 ± 85 (522 ± 84), 532 ± 86 (560 ± 87), and 549 ± 99 (575 ± 107)m. Repeated 6MWDs strongly correlated at each assessment point, with intraclass correlation coefficients of .96 (95% confidence interval [CI], 0.93-.98), .97 (95% CI, .92-.98), and .94 (95% CI, .89-.97), respectively. Relative increases in mean 6MWD from 6MWT1 to 6MWT2 at each assessment point were 3%, 5%, and 5%, respectively (P<.001 in each case). Differences in walking speed derived from 6MWD1 and 6MWD2 did not translate into differences in exercise prescription.

Conclusions: The difference between 6MWD1 and 6MWD2 was consistent regardless of previous exposure to 6MWTs. A single 6MWT was as effective as 2 repeated 6MWTs for outcome measurement and exercise prescription. We therefore recommend that when 6MWDs are used for CR outcome measurement, either a single 6MWT be used or the number of 6MWTs performed be consistent at all assessment points.