Variables Measured During Cardiopulmonary Exercise Testing as Predictors of Mortality in Chronic Systolic Heart Failure

Abstract Background Data from a cardiopulmonary exercise (CPX) test are used to determine prognosis in patients with chronic heart failure (HF). However, few published studies have simultaneously compared the relative prognostic strength of multiple CPX variables. Objectives The study sought to describe the strength of the association among variables measured during a CPX test and all-cause mortality in patients with HF with reduced ejection fraction (HFrEF), including the influence of sex and patient effort, as measured by respiratory exchange ratio (RER). Methods Among patients (n = 2,100, 29% women) enrolled in the HF-ACTION (HF-A Controlled Trial Investigating Outcomes of exercise traiNing) trial, 10 CPX test variables measured at baseline (e.g., peak oxygen uptake [V o2 ], exercise duration, percent predicted peak V o2 [%ppV o2 ], ventilatory efficiency) were examined. Results Over a median follow-up of 32 months, there were 357 deaths. All CPX variables, except RER, were related to all-cause mortality (all p < 0.0001). Both %ppV o2 and exercise duration were equally able to predict (Wald chi-square: ∼141) and discriminate (c-index: 0.69) mortality. Peak V o2 (ml·kg–1 ·min–1 ) was the strongest predictor of mortality among men (Wald chi-square: 129) and exercise duration among women (Wald chi-square: 41). Multivariable analyses showed that %ppV o2 , exercise duration, and peak V o2 (ml·kg–1 ·min–1 ) were similarly able to predict and discriminate mortality. In men, a 10% 1-year mortality rate corresponded to a peak V o2 of 10.9 ml·kg–1 ·min–1 versus 5.3 ml·kg–1 ·min–1 in women. Conclusions Peak V o2 , exercise duration, and % ppV o2 carried the strongest ability to predict and discriminate the likelihood of death in patients with HFrEF. The prognosis associated with a given peak V o2 differed by sex. (Exercise Training Program to Improve Clinical Outcomes in Individuals With Congestive Heart Failure; NCT00047437 )