Clinical correlates and outcome associated with changes in 6-minute walking distance in patients with heart failure: findings from the BIOSTAT-CHF study

BACKGROUND: The 6-minute walk test (6MWT) is a simple and inexpensive way of measuring exercise capacity in patients with heart failure (HF) that predicts morbidity and mortality. However, there are few reports from large multicentre cohorts assessing the predictive value of baseline and changing walk distance. METHODS AND RESULTS: In BIOSTAT-CHF, a 6MWT was performed at baseline (n = 1714) and 9 months (n = 1520). Cox proportional hazards models were used to assess the associations between 6MWT distance and the composite of HF hospitalization and/or death. Median follow-up was 21 months. The median (pct25-75 ) of the 6MWT distance at baseline was 300 m (200-388 m). Independent predictors of a shorter 6MWT distance included older age, female sex, higher heart rate, New York Heart Association class III/IV, orthopnoea, ischaemic heart disease, a previous stroke, current malignancy, and higher N-terminal pro-B-type natriuretic peptide (all P < 0.05). Patients in the lowest baseline 6MWT tertile (≤ 240 m) were less likely to receive guideline-recommended doses of disease-modifying therapies (P < 0.05). Compared to patients in the highest baseline 6MWT tertile (> 360 m), those in the lowest and middle tertiles had a worse prognosis [adjusted hazard ratio (HR) 1.73, 95% confidence interval (CI) 1.38-2.18]. Patients with a decrease in the distance walked had a worse prognosis (adjusted HR for each 50 m decrease 1.09, 95% CI 1.06-1.12). 6MWT distance was not modified by treatment up-titration nor the 6MWT improved the BIOSTAT-CHF prognostic models. CONCLUSIONS: The 6-minute walk test distance at baseline and a decline in walking distance were both associated with worse prognosis but did not improve the prognostic models. 6MWT distance was not modified by treatment up-titration and its use for assessing the benefits of pharmacologic treatment up-titration may be limited.