Do repeat 6-minute walk tests provide clinically meaningful information in symptomatic heart failure?

BACKGROUND: Two baseline 6-minute walk tests (6MWTs) have been recommended to mitigate a potential learning effect when assessing exercise performance, but the magnitude of any learning effect in heart failure with reduced ejection fraction (HFrEF) is uncertain. Using the Sildenafil in Heart Failure (SilHF) trial, in which two baseline 6MWTs were performed (screening and inclusion), we assessed a potential learning effect in this population. We also assessed whether choice of baseline test affected associations with longitudinal patient-reported outcomes and compared our findings to reports in the current literature. METHODS AND RESULTS: In SilHF, 69 patients with HFrEF and evidence of pulmonary hypertension performed 6MWTs at screening and again at study inclusion. Tests were performed no more than two weeks apart on unchanged optimal medical therapy. Only the inclusion 6MWT was used for efficacy evaluation of sildenafil. Screening and inclusion distances were compared using a paired t-test. Additionally, we assessed whether each baseline 6MWT (screening and inclusion) correlated with longitudinal patient-reported outcome measures. Outcomes included the Kansas City Cardiomyopathy Questionnaire (KCCQ) and the EuroQoL-5D visual analogue scale (EQ-5D VAS), assessed at 24 weeks. Although the inclusion 6MWT distance was statistically significantly higher than the screening test (+11.3 m, 95% CI 2.6 to 20.1, p = 0.012), the two baseline tests demonstrated very similar correlation coefficients with longitudinal patient-reported outcomes. CONCLUSION: We observed a small increase in 6MWD between repeat baseline tests, consistent with a modest learning effect that is unlikely to be clinically meaningful. Both initial 6MWTs showed similar significant correlations with other longitudinal patient-reported outcome measures. In symptomatic HFrEF with pulmonary hypertension, a single baseline 6MWT may be sufficient to assess functional capacity.