Targeting of High Peak Respiratory Exchange Ratio Is Safe and Enhances the Prognostic Power of Peak Oxygen Uptake for Heart Failure Patients

Abstract

BACKGROUND: Peak oxygen uptake (V̇O2) and ventilatory efficiency (V̇E/V̇CO2slope) measured on cardiopulmonary exercise testing (CPX) are prognostic indicators in heart failure (HF) patients, but peak V̇O2is influenced by patient effort. In CPX targeting a peak respiratory exchange ratio (pRER; an objective index of effort adequacy) higher than the commonly recommended level, we assessed the safety and prognostic value of CPX parameters compared with non-CPX parameters. METHODS AND RESULTS: We studied 283 consecutive HF patients with left ventricular ejection fraction (LVEF) ≤45% (mean, 26.3%) who underwent CPX targeting pRER >1.20. The attained pRER (mean, 1.26) was consistently high irrespective of LVEF, and there was no major exercise-related adverse event. The composite of all-cause death or HF hospitalization occurred in 111 patients (39%) during a median follow-up of 47 months. Among well-known prognostic markers, peak V̇O2was the most powerful predictor of outcome as both a continuous and an optimal dichotomous variable, followed by V̇E/V̇CO2slope. On multivariate analysis, peak V̇O2was a significant independent predictor, whereas V̇E/V̇CO2slope, B-type natriuretic peptide, and LVEF were not. CONCLUSIONS: In CPX targeting pRER >1.20 for HF patients, peak V̇O2is the most powerful among well-known predictors, without an increased risk of exercise-related events. These findings advocate a high target pRER in CPX even in advanced HF.