Usefulness of physical function sub-item of SF-36 survey to predict exercise intolerance in patients with heart failure

Background Exercise intolerance is widely known to be a major cardinal symptom in patients with heart failure (HF), but due to the recent coronavirus disease 2019 epidemic, it is still difficult to directly measure exercise tolerance in many hospitals and facilities. The 36-Item Short-Form Health Survey physical functioning (SF-36PF) pertain to lower extremity functioning and walking. The purpose of this study was to investigate whether SF-36PF is a useful predictor of exercise intolerance and to provide its optimal cut-off value for patients with HF. Methods and results SF-36PF and 6-min walking distance (6MWD) were evaluated in 372 consecutive patients with HF. Exercise intolerance was defined at 6MWD cut-offs of 200, 300, and 400 m. The addition of SF-36PF to the pre-existing determinants of exercise tolerance significantly improved the area under the curve scores (0.85 vs. 0.89, P = 0.011 for 6MWD <200 m; 0.90 vs. 0.93, P = 0.001 for 6MWD <300 m; 0.88 vs. 0.90, P = 0.021 for 6MWD <400 m) for the predictive effect on exercise intolerance. The cut-off values of SF-36PF for predicting exercise intolerance defined by 6MWD <200, 300, and 400 m were 45, 50, and 70, respectively. Conclusions SF-36PF is a useful tool as an alternative index to predict exercise intolerance in patients with HF.