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

Abstract

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 (ΔPETO₂ ) may represent predominantly peripheral factors. This study aimed to verify the prognostic significance of ΔPETO₂ for major adverse cardiac and cerebrovascular events (MACCE) in cardiac patients, including comparison with the minute ventilation-carbon dioxide production relationship (VE/VCO₂ slope), and peak oxygen uptake (VO₂ ).

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 ΔPETO₂ , VE/VCO₂ slope, and peak VO₂ to predict MACCE was examined.

Results: Optimal cut-off values for predicting MACCE were 2.0 mmHg for ΔPETO₂ (area under the curve [AUC]: 0.829), 29.8 for VE/VCO₂ slope (AUC: 0.734), and 19.0 mL/min/kg for peak VO₂ (AUC: 0.755). The AUC of ΔPETO₂ was higher than those of VE/VCO₂ slope and peak VO₂ . The MACCE-free survival rate was significantly lower in the ΔPETO₂ ≤ 2.0 group versus the ΔPETO₂ > 2.0 group (44.4% vs. 91.2%, p < 0.001). ΔPETO₂ ≤ 2.0 was an independent predictor of MACCE after adjustment for age and VE/VCO₂ slope (hazard ratio [HR], 7.28; p < 0.001) and after adjustment for age and peak VO₂ (HR, 6.52; p < 0.001).

Conclusion: ΔPETO₂ was a strong predictor of MACCE independent of and superior to VE/VCO₂ slope and peak VO₂ in patients with cardiac disease.

Keywords: cardiac disease; cardiopulmonary exercise testing; end-tidal oxygen partial pressure; major adverse cardiac and cerebrovascular events; prognostic predictive factor.