Predictive value of exercise PETO 2 changes for major adverse cardiovascular events in ischaemic heart disease: An exploratory study

The difference in end‐tidal oxygen partial pressure (ΔPETO 2 ) 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 ΔPETO 2 from the CPET data. Receiver operating characteristic analysis identified the ΔPETO 2 cutoff value in predicting MACE occurrence, after which patients were divided into low ΔPETO 2 and high ΔPETO 2 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 ΔPETO 2 as the dependent variable. Among 168 cases (mean age 66.2 ± 10.1 years; 143 males), 22 patients (13%) experienced MACE. The optimal ΔPETO 2 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 ΔPETO 2 ≤ 2.5 group compared to the ΔPETO 2 > 2.5 group. Multiple regression analysis identified peak oxygen pulse (peak O 2 pulse), ankle‐brachial index (ABI), and dyslipidemia (DL) as independent factors associated with ΔPETO 2 . ΔPETO 2 may serve as a useful early indicator for predicting high risk of MACE in IHD before the onset of heart failure. Additionally, peak O 2 pulse, ABI, and DL were identified as factors influencing ΔPETO 2 , suggesting that blood flow to the lower limbs may impact ΔPETO 2 .