The Diagnostic Role Of End-Tidal CO2 To Distinguish Unstable Angina Pectoris In Patients With Chest Pain

Abstract

Objective: Unstable angina pectoris (UAP), one of the acute coronary syndrome (ACS) types, is difficult to identify from non-cardiac chest pain (non-CCP), hence various strategies are applied for accurate diagnosis. This study aims to examine whether non-invasively measured end-tidal CO2 (ETCO2) can detect UAP in patients admitted to the emergency department (ED) with chest pain in the lack of a cardiovascular history. Methods: This research was conducted as a prospective observational study. The individuals were separated into two groups based on the inclusion and exclusion criteria: 75 patients with non-CCP and 75 UAP. Analyses of receiver operating characteristics (ROC) were utilized to define the diagnostic value cutoff. Using univariate regression analysis, the odds ratio of ETCO2 (with 95%CI) was computed for UAP prediction. Results: ETCO2 levels were substantially lower in the UAP group compared to the non-CCP group (p<0.001). Analysis of the ROC curve revealed that a decreased ETCO2 <35 predicted UAP with 78% sensitivity and 89% specificity (AUC:0.81, p <0.001). In addition, the negative predictive value was 71.6%, and the positive predictive value was 79.4%. Patients with UAP were 8.84 times more likely to have ETCO2 <35 than patients with non-CCP. Conclusion: UAP may be differentiated from non-CCP by ETCO2 measured as a non-invasive parameter in patients with chest pain.