Six-minute walking test but not ejection fraction predicts mortality in elderly patients undergoing cardiac rehabilitation following coronary artery bypass grafting

Abstract

Age-related effects on the ability of 6-min walking test (6MWT) and ejection fraction (EF) to predict mortality in coronary artery bypass grafting (CABG) patients undergoing cardiac rehabilitation (CR) is still debated. In order to verify the role of 6MWT and EF on all-cause mortality in patients undergoing CR following CABG, 882 CABG patients undergoing CR stratified in adults (<65 years) and elderly (≥65 years) were studied. At the admission, EF was 52.6 ± 9.1% in adults and 51.3 ± 8.9% in elderly (p = 0.234, NS) while 6MWT was 343.8 ± 93.5 m in adults and 258.9 ± 95.7 m in elderly (p < 0.001). After 42.9 ± 14.1 months follow up, mortality was 8.2% in adults and 10.9% in elderly (p = 0.176, NS). Cox regression analysis shows that EF ≥ 50% and 6MWT ≥300 m are protective on mortality in all CABG patients before CR. However, EF ≥50% in adults (HR 0.18, 95% CI 0.06-0.49, p < 0.005) but not in elderly (HR 1.16, 95% CI 0.45-3.42, p = 0.354, NS) and 6MWT ≥300 m in elderly (HR 0.34, 95% CI 0.10-0.79, p = 0.033) but not in adults (HR 0.76, 95% CI 0.31-2.12, p = 0.654, NS) exert a protective role on mortality. Our results indicate that both EF ≥ 50% and 6MWT ≥ 300 m independently protect against mortality in CABG patients before CR. However, their protective role is age dependent. In fact, EF ≥ 50% is protective in adults but not in elderly while 6MWT ≥ 300 m is protective in elderly but not in adult patients.