External validation of the EuroSCORE I and II prediction models for postoperative 30-day mortality in patients with infective endocarditis: results from a nationwide prospective registry

Abstract Background The European System for Cardiac Operative Risk Evaluation (EuroSCORE) I and II are widely used risk models for predicting 30-day mortality after cardiac surgery [1,2]. It is suggested that both models overpredict 30-day mortality in specific groups of patients [3,4]. However, their performance in patients with infective endocarditis (IE) is unclear, since few IE patients were included in the development cohort (<500 patients for EuroSCORE II). Moreover, all previous studies that have evaluated the performance of EuroSCORE models in IE had small sample sizes [5-7]. Purpose To externally validate the EuroSCORE I and II prediction models in patients with IE in a nationwide prospective registry. Methods The Netherlands Heart Registration (NHR) is a national prospective registry of all patients undergoing cardiac surgeries and interventions in The Netherlands. It collects clinically relevant data, such as medical history and postoperative complications, and follows patients up to many years after surgery. In addition, the EuroSCORE I and II are recorded for each individual. For this study, we included all patients with IE who underwent cardiac surgery in the Netherlands between 2013 and 2021. The predictive performance of EuroSCORE I and II was assessed by discrimination and calibration. Discrimination was assessed by the area under the curve (AUC), and reflects how well the model discriminates between patients with and without the outcome of interest. Calibration describes the agreement between observed and predicted risks and was assessed by calibration in the large (average observed risk versus average predicted risk) and calibration plots. Results We included 2577 IE patients (median age 64 years (IQR 53 – 71), 76.2% male, 33.6% with previous cardiac surgery of which 94.3% previous valve surgery). Overall 30-day mortality was 10.2%. The mean EuroSCORE I and II were 27.9% (SD 22.1) and 14.9% (SD 16.3) respectively. The AUCs for EuroSCORE I and II were 0.73 (95% CI 0.70 – 0.76) and 0.72 (95% CI 0.69 – 0.75) (Figure 1). Calibration in the large showed that both models overpredict risks, with an observed to expected ratio of 0.37 for EuroSCORE I and 0.68 for EuroSCORE II. The calibration plot showed that EuroSCORE I overpredicts risks across the full range (Figure 2A). Calibration of the EuroSCORE II was reasonable in patients with low predicted probability, but overpredicts risks when the predicted probability was >20% (Figure 2B). Conclusion Both EuroSCORE I and II substantially overestimate 30-day mortality risk after cardiac surgery in IE patients. Use of EuroSCORE I and II may therefore lead to disadvantageous decision making if patients with a high predicted 30-day mortality risk are subsequently withheld from indicated surgical treatment (class I or IIa) [8]. Further research will recalibrate the EuroSCORE II for IE patients and assess the influence of its individual parameters on 30-day mortality in this population.Receiver operating characteristic curvesCalibration plots of EuroSCORE I and II