Predictive value of exercise PETO2 changes for major adverse cardiovascular events in ischaemic heart disease: An exploratory study

Abstract

The difference in end-tidal oxygen partial pressure (ΔPETO₂) between rest and anaerobic threshold exercise is reportedly a predictor of major adverse cardiovascular events (MACE) in heart disease patients, but its predictive accuracy has not been verified in ischaemic heart disease (IHD). We analyzed the incidence of MACE within 3 years after cardiopulmonary exercise testing (CPET) in IHD patients, and calculated ΔPETO₂ from the CPET data. Receiver operating characteristic analysis identified the ΔPETO₂ cutoff value in predicting MACE occurrence, after which patients were divided into low ΔPETO₂ and high ΔPETO₂ groups. Kaplan-Meier analysis using the log-rank test was performed to compare the incidence of MACE within 3 years, and multiple regression analysis was conducted with ΔPETO₂ as the dependent variable. Among 168 cases (mean age 66.2 ± 10.1 years; 143 males), 22 patients (13%) experienced MACE. The optimal ΔPETO₂ cutoff value in predicting MACE was 2.5 mmHg (area under the curve 0.888, sensitivity 77%, specificity 90%). Kaplan-Meier analysis revealed that the MACE incidence rate was significantly higher in the ΔPETO₂ ≤ 2.5 group compared to the ΔPETO₂ > 2.5 group. Multiple regression analysis identified peak oxygen pulse (peak O₂ pulse), ankle-brachial index (ABI), and dyslipidemia (DL) as independent factors associated with ΔPETO₂. ΔPETO₂ may serve as a useful early indicator for predicting high risk of MACE in IHD before the onset of heart failure. Additionally, peak O₂ pulse, ABI, and DL were identified as factors influencing ΔPETO₂, suggesting that blood flow to the lower limbs may impact ΔPETO₂.