Comparative Predictive Performance of EuroSCORE II and the STS Score for Postoperative Cardiopulmonary Complications in Older Adults Undergoing Cardiac Surgery

Background/Objectives: Accurate preoperative risk stratification is critical in older adults undergoing cardiac surgery, particularly for predicting postoperative cardiopulmonary complications (PCPCs). Although EuroSCORE II and the Society of Thoracic Surgeons (STS) score are widely used to estimate mortality risk, their ability to predict morbidity in older adults remains unclear. This study compared the performance of EuroSCORE II and the STS score in predicting PCPCs after on-pump cardiac surgery. Methods: This retrospective cohort study included patients aged ≥ 60 years who underwent elective on-pump cardiac surgery at Songklanagarind Hospital between January 2017 and December 2022. PCPCs included prolonged mechanical ventilation (>48 h), reintubation within 72 h, pneumonia, respiratory failure, new-onset atrial fibrillation, or low cardiac output requiring inotropic or mechanical support. Predictive performance was evaluated using receiver operating characteristic (ROC) curve analysis, logistic regression, calibration analysis, and overall prediction accuracy measures. Results: Among 638 patients, 273 (42.8%) developed PCPCs. Both scores were significantly associated with PCPCs. EuroSCORE II showed modest discrimination (area under the curve [AUC]: 0.581; 95% CI: 0.536–0.626); in contrast, the STS Score performed better (AUC: 0.625; 95% CI: 0.580–0.669; p = 0.017). In logistic regression, EuroSCORE II (odds ratio [OR]: 1.06; 95% CI: 1.01–1.10; p = 0.006) and the STS Score (OR: 1.05; 95% CI: 1.03–1.07; p < 0.001) were independently associated with PCPCs. Both models demonstrated acceptable calibration, although STS score showed better overall predictive performance than EuroSCORE II. Conclusions: EuroSCORE II and the STS score were both associated with postoperative cardiopulmonary complications but demonstrated only modest discriminative ability. Although the STS score performed significantly better than EuroSCORE II, neither model achieved sufficient accuracy for clinically meaningful individualized risk prediction.