['The resting partial pressure of end-tidal carbon dioxide (Petco2) has been shown to reflect cardiac performance in acute care settings in patients with heart failure (HF). The purpose of the present study was to compare the prognostic ability of the partial pressure of Petco2 at rest to other commonly collected resting variables in patients with systolic HF.', 'A total of 353 patients (mean age 58.6+/-13.7, 72% male) with systolic HF were included in this study. All patients underwent cardiopulmonary exercise testing where New York Heart Association (NYHA) class, resting Petco2, peak oxygen consumption, and the minute ventilation/carbon dioxide production slope were determined. Subjects were then followed for major cardiac events (mortality, left ventricular assist device implantation implantation, urgent heart transplantation).', 'There were 104 major cardiac events during the 23.6+/-17.0-month tracking period. Multivariate Cox regression analysis revealed NYHA class (chi2 28.7, P<.001), left ventricular ejection fraction (residual chi2 21.7, P<.001), and resting Petco2 (residual chi2 14.1, P<.001) were all prognostically significant and retained in the regression. In a separate Cox regression analysis, left ventricular ejection fraction (residual chi2 8.8, P=.003), NYHA class (residual chi2 7.7, P=.005), and resting Petco2 (residual chi2 5.7, P=.02) added prognostic value to the minute ventilation/carbon dioxide production slope (chi2 26.0, P<.001).'] Does the partial pressure of resting end-tidal carbon dioxide predict major cardiac events in patients with systolic heart failure?