Prognostic value of end-tidal carbon dioxide during exercise testing in heart failure

Background: The partial pressure of end-tidal carbon dioxide production (P_ETCO₂) at ventilatory threshold (VT) has been shown to be strongly correlated with cardiac output during exercise in patients with heart failure (HF), but few data are available regarding its prognostic utility. Aims: The purpose of this study was to assess the ability of P_ETCO₂ to predict cardiac-related events in a group of subjects with HF. Methods: One hundred and thirty subjects diagnosed with compensated HF underwent cardiopulmonary exercise testing (CPX). Peak oxygen consumption (VO₂), the minute ventilation-carbon dioxide production (VE/VCO₂) slope and P_ETCO₂ were determined. Results: Receiver operating characteristic (ROC) curve analysis revealed that P_ETCO₂ at the ventilatory threshold (VT) was a significant predictor of cardiac-related events (ROC area = 0.82, p <0.001). The optimal P_ETCO₂ at a VT threshold value for separating high (≤) and low (>) risk groups was 36.1 mm Hg (77% sensitivity, 69% specificity). In a multivariate Cox regression analysis, P_ETCO₂ at VT added significant predictive value to the VE/VCO₂ slope and peak VO₂. Conclusion: These results indicate that P_ETCO₂ during CPX is a significant predictor of cardiac-related events in patients with HF. Clinical assessment of this variable in patients with HF undergoing CPX may therefore be warranted.