Relationships between changes in patient-reported health status and functional capacity in outpatients with heart failure

Background: Heart failure trials use a variety of measures of functional capacity and quality of life. Lack of formal assessments of the relationships between changes in multiple aspects of patient-reported health status and measures of functional capacity over time limits the ability to compare results across studies. Methods: Using data from HF-ACTION (N = 2331), we used the Pearson correlation coefficients and predicted change scores from linear mixed-effects modeling to demonstrate the associations between changes in patient-reported health status measured with the EQ-5D visual analog scale and the Kansas City Cardiomyopathy Questionnaire (KCCQ) and changes in peak VO ₂ and 6-minute walk distance at 3 and 12 months. We examined a 5-point change in KCCQ within individuals to provide a framework for interpreting changes in these measures. Results: After adjustment for baseline characteristics, correlations between changes in the visual analog scale and changes in peak VO₂ and 6-minute walk distance ranged from 0.13 to 0.28, and correlations between changes in the KCCQ overall and subscale scores and changes in peak VO₂ and 6-minute walk distance ranged from 0.18 to 0.34. A 5-point change in KCCQ was associated with a 2.50-mL kg^-1 min^-1 change in peak VO₂ (95% CI 2.21-2.86) and a 112-m change in 6-minute walk distance (95% CI 96-134). Conclusions: Changes in patient-reported health status are not highly correlated with changes in functional capacity. Our findings generally support the current practice of considering a 5-point change in the KCCQ within individuals to be clinically meaningful.