Changes in 6-min walk test is an independent predictor of death in chronic heart failure with reduced ejection fraction.

ABSTRACT

AIMS: Functional capacity provides important clinical information in patients with heart failure (HF) and reduced ejection fraction (HFrEF). The 6-min walk test (6MWT) is a simple and inexpensive tool for assessing functional capacity and risk. Although change in 6MWT is frequently used as a surrogate outcome in HF trials, the association with mortality is unclear. We aimed to assess the prognostic importance of changes in 6MWT. METHODS AND RESULTS: Patients with chronic HFrEF referred to HF outpatient clinics in Norway completed a 6MWT at the first visit (baseline) and at a stable follow-up visit after treatment optimization (follow-up). Absolute and relative changes in 6MWT were analysed in association with mortality risk using Cox regression models and flexible cubic splines. The study included 3636 HFrEF patients aged 67.3 ± 11.6 years, 23% women, with left ventricular ejection fraction 30 ± 7%. At baseline, mean 6MWT was 438 ± 125 m, median N-terminal pro-B-type natriuretic peptide (NT-proBNP) 1574 (732-3093) ng/L, and 27% had New York Heart Association (NYHA) class III/IV. After optimization of guideline-directed medical therapy (median 147 [86-240] days), 6MWT increased by mean 40 ± 74 m, NT-proBNP decreased by median 425 (14-1322) ng/L, and NYHA class improved in 38% of patients. Patients with greater improvements in 6MWT were younger, with greater improvements in NYHA class (r = 0.27, p < 0.001) and larger reductions in NT-proBNP concentrations (r = 0.19, p < 0.001). After mean 845 ± 595 days, 419 (11.5%) patients were dead. Both absolute and relative changes in 6MWT were non-linearly associated with survival, attenuating as 6MWT increased. A 50 m increase in 6MWT was associated with a 17% lower mortality risk (hazard ratio 0.84, 95% confidence interval 0.77-0.90, p < 0.001) in the fully adjusted model, including changes in NYHA class, NT-proBNP concentrations, and other established risk factors. The associations were more pronounced in patients with lower baseline 6MWT and higher age. CONCLUSION: Improvement in 6MWT in patients with HFrEF is associated with increased survival, independent of changes in NT-proBNP and NYHA class. These findings support 6MWT change as a surrogate outcome in HF trials.