Defining the Optimal Prognostic Window for Cardiopulmonary Exercise Testing in

Background: Ventilatory efficiency (VE/VCO2 slope) and peak oxygen consumption (VO2) provide robust prognostic information in patients with heart failure (HF) undergoing cardiopulmonary exercise testing (CPX). The purpose of the present study is to assess the change in prognostic characteristics of CPX at different time intervals. Methods and Results: Seven hundred and 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 four year period. All event-free subjects were tracked for at least three years. Mean VE/VCO2 slope and peak VO2 were 35.0 ±10.0 and 16.0 ±6.4 mlO2 kg min, respectively. There were a total of 263 major cardiac events (199 deaths/45 transplants/19 left ventricular assist device implantations). Both continuous and dichotomous expressions of the VE/VCO2 slope and peak VO2 were prognostically significant up to 18 months post CPX. Continuous and dichotomous expressions of the VE/VCO2 slope remained prognostically significant up to 36 months post CPX while 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 while 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 two years. The VE/VCO2 slope is the superior predictor of adverse events throughout follow-up, although peak VO2 provides additive prognostic information during the first two years of follow-up.