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 (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.