Defining the optimal prognostic window for cardiopulmonary exercise testing in patients with heart failure

Background: Ventilatory efficiency (VE/VCO2 slope) and peak oxygen consumption (VO) provide robust prognostic information in patients with heart failure undergoing cardiopulmonary exercise testing (CPX). The purpose of this study is to assess the change in prognostic characteristics of CPX at different time intervals. Methods and Results: Seven hundred ninety-one subjects (74% male, mean age: 60.7±12.9 years, ejection fraction: 34.6±15.0%, ischemic etiology: 51%) underwent CPX and were tracked for major cardiac events over a 4-year period. All event-free subjects were tracked for at least 3 years. Mean VE/VCO2 slope and peak VO2 were 35.0±10.0 and 16.0±6.4 mL O2 ·kg-1 ·min-1, respectively. There were a total of 263 major cardiac events (199 deaths, 45 transplants, and 19 left ventricular assist device implantations). Both continuous and dichotomous expressions of the VE/VCO 2 slope and peak VO2 were prognostically significant up to 18 months post-CPX. Continuous and dichotomous expressions of the VE/VCO 2 slope remained prognostically significant up to 36 months post-CPX, whereas peak VO2 was not predictive during the third and fourth year of follow-up. In a multivariate analysis, the VE/VCO2 slope was consistently the superior prognostic marker, whereas peak VO2 added predictive value and was retained in the regression up to 18 months post-CPX. Conclusions: These results indicate that commonly assessed CPX variables retain prognostic value for at least 2 years. The VE/VCO2 slope is the superior predictor of adverse events throughout follow-up, although peak VO 2 provides additive prognostic information during the first 2 years of follow-up.