The prognostic value of serial six-minute walk testing for mortality prediction in heart failure patients

The Six-Minute Walk Test (6MWT) is a widely used, low-cost measure of functional capacity in heart failure patients. While baseline 6MWT distance is a known prognostic marker, the added value of serial assessments remains underexplored. This study examined whether serial 6MWT measurements and their temporal trajectories improve mortality prediction.

This retrospective cohort study included 1,114 patients with heart failure who underwent at least one 6MWT at Shaare Zedek Medical Center during 2014-2023. All-cause mortality was the primary outcome. Two modelling approaches were applied: 1) a Cox proportional hazards model using a single 6MWT assessment; and 2) a joint model incorporating repeated 6MWT assessments. Models were evaluated at baseline and after 12 months, for forward predictions of 36- and 60-month mortality, with performance assessed using the area under the curve (AUC) and Brier Score on data not used for model development.

The joint models demonstrated superior predictive accuracy; in patients with ≥3 6MWTs, AUC improved by 0.116 (95% CI: 0.010-0.238) and Brier Score decreased by -0.032 (95% CI: -0.072, -0.003) at 36 months. In the joint model survival submodel, each 10-meter increase in 6MWT distance was associated with reduced mortality risk (HR=0.95, 95% CrI: 0.93-0.96), as was a 10-meter/year predicted improvement in slope (HR=0.86, 95% CrI: 0.80-0.97).

Serial 6MWT assessment offers prognostic value beyond a baseline measurement. Both absolute walking distance and improvement over time were independently associated with mortality. Modelling functional trajectories over time may improve mortality risk prediction and support personalized clinical management in heart failure.