End‐tidal oxygen partial pressure is a strong prognostic predictive factor in patients with cardiac disease

Background Cardiopulmonary exercise testing (CPET) variables represent central and peripheral factors and combined factors in the pathology of patients with cardiac disease. The difference in end‐tidal oxygen partial pressure from resting to anaerobic threshold (ΔPETO 2 ) may represent predominantly peripheral factors. This study aimed to verify the prognostic significance of ΔPETO 2 for major adverse cardiac and cerebrovascular events (MACCE) in cardiac patients, including comparison with the minute ventilation–carbon dioxide production relationship (VE/VCO 2 slope), and peak oxygen uptake (VO 2 ). Methods In total, 185 patients with cardiac disease who underwent CPET were consecutively enroled in this retrospective study. The primary endpoint was 3‐year MACCE. The ability of ΔPETO 2 , VE/VCO 2 slope, and peak VO 2 to predict MACCE was examined. Results Optimal cut‐off values for predicting MACCE were 2.0 mmHg for ΔPETO 2 (area under the curve [AUC]: 0.829), 29.8 for VE/VCO 2 slope (AUC: 0.734), and 19.0 mL/min/kg for peak VO 2 (AUC: 0.755). The AUC of ΔPETO 2 was higher than those of VE/VCO 2 slope and peak VO 2 . The MACCE‐free survival rate was significantly lower in the ΔPETO 2 ≤ 2.0 group versus the ΔPETO 2 > 2.0 group (44.4% vs. 91.2%, p < 0.001). ΔPETO 2 ≤ 2.0 was an independent predictor of MACCE after adjustment for age and VE/VCO 2 slope (hazard ratio [HR], 7.28; p < 0.001) and after adjustment for age and peak VO 2 (HR, 6.52; p < 0.001). Conclusion ΔPETO 2 was a strong predictor of MACCE independent of and superior to VE/VCO 2 slope and peak VO 2 in patients with cardiac disease.