Interaction of Risk of Death and Improvement in Functional Capacity After Cardiac Rehabilitation on Heart Failure Prognosis

Whether risk of death interacts with change in 6-minute walking test (6MWT) distance after cardiac rehabilitation (CR) on heart failure (HF) prognosis is unknown. We studied 1,569 patients with HF admitted to 6 inpatient CR units. A 6MWT was performed at admission to and at discharge from CR. The primary outcome was 3-year mortality. The interaction of baseline risk and 50-meter increase in 6MWT distance on the primary outcome was tested using a Cox regression model with an interaction term between baseline risk and 50-meter increase. To further illustrate the interaction between baseline risk and change in 6MWT distance, participants were stratified into low- and high-risk subgroups. The p value for the interaction was 0.588. Three-year mortality was 16.1% in the low-risk and 53.7% in the high-risk subgroup. 43.0% of the low-risk and 43.4% of the high-risk patients achieved an increase ≥50 meters in 6MWT distance. The adjusted hazard ratio of 3-year mortality for the patients who achieved a 50-meter increase in 6MWT distance was 0.67 (0.47–0.96; p = 0.030) in the low-risk and 0.75 (0.61–0.91; p = 0.005) in the high-risk subgroup. These findings suggest that improvement in functional capacity after CR is associated with improved survival regardless of baseline risk of death.