Submaximal exercise gas exchange is an important prognostic tool to predict adverse outcomes in heart failure

AimsTraditionally, VO₂peak has been used to determine prognosis in heart failure; however, this measure has limitations. Hence, other exercise and gas exchange parameters measured submaximally, e.g. breathing efficiency (VE/VCO₂), end-tidal CO₂ (P_ETCO₂), oxygen uptake efficiency slope (OUES), and circulatory power [systolic blood pressure (SBP)], have been investigated. The aim of this study was to investigate the prognostic relevance of submaximal exercise gas exchange in heart failure patients.Method and resultsOne hundred and thirty-two consecutive heart failure patients (mean age 56 ± 12 years, ejection fraction 29 ± 11) performed peak treadmill testing. Gas exchange and haemodynamic variables were measured continuously. Gas exchange data obtained from the first 2 min of exercise and at a respiratory exchange ratio (RER) of 0.9 were the measurements of interest. Over a median follow-up period of 62.4 (range 0114) months, there were 44 endpoints (death or transplant). Univariate analysis demonstrated submaximal predictors of survival, which included V _E/VCO₂ slope and ratio, PETCO₂, OUES, and circulatory power (P≤ 0.01). When these and additional submaximal variables were included together in the multivariable analysis, the strongest submaximal exercise predictive model (C-statistic 0.75) comprised data from the first stage of exercise (VE and circulatory power) and at an RER of 0.9 (V _E/VCO₂ ratio). The inclusion of VO2peak and demographic data, with submaximal data (V_E/VCO₂ ratio at an RER 0.9), increased the predictiveness of the model (C-statistic 0.78). ConclusionSubmaximal exercise measures provide useful prognostic information for predicting survival in heart failure. This form of testing is logistically easier, cheaper, and safer for patients compared with maximal exercise.