Oxygen consumption and carbon-dioxide recovery kinetics in the prediction of coronary artery disease severity and outcome

Background Revascularization appears to be beneficial only in patients with high levels of ischemia. This study examined the utility of gas analysis during the recovery phase of cardiopulmonary exercise testing (CPET) in predicting coronary artery disease (CAD) severity and prognosis. Methods 40 Caucasian patients (21.2% females), mean age 63.5 ± 7.6 with significant coronary artery lesions (≥ 50%) were studied. Within two months of coronary angiography, CPET on a treadmill (TM) and recumbent ergometer (RE) were performed on two visits 2–4 days apart; subjects were subsequently followed 32 ± 10 months. Myocardial wall motion was recorded by echocardiography at rest and peak exercise. Ischemia was quantified by the wall motion score index (WMSI). Results Mean ejection fraction was 56.7 ± 9.6%. Patients with 1–2 stenotic coronary arteries (SCA) showed a poorer CPET response during the recovery phase than patients with 3-SCA. ROC analysis revealed the change of carbon-dioxide output (∆ VCO₂) recovery/peak (area under ROC curve 0.77, p = 0.02, Sn = 87.5%, Sp = 70.4%) and oxygen uptake (∆ VO₂) recovery/peak during TM CPET (area under ROC curve 0.76, p = 0.03, Sn 75.0%, Sp 77.8%) were significant in distinguishing between 1-2-SCA and 3-SCA. The same variables predicted ΔWMSI peak/rest on univariate analysis (p < 0.05). Multivariate Cox analysis revealed a high predictive value of ∆ VO₂ recovery/peak obtained during TM CPET for composite endpoint of cumulative cardiac events (HR = 1.27, CI = 1.07–1.51, p = 0.008). Conclusions The current study suggests CPET parameters in recovery hold predictive value for CAD severity and prognosis. TM testing seems to be a better approach in the assessment of CAD severity and prognosis.