Enhanced Risk Stratification in Infective Endocarditis Surgery: A Comprehensive External Validation of All Available Mortality Prediction Scores.

Background: Several prognostic models have been developed to estimate operative mortality in patients undergoing surgery for infective endocarditis (IE). However, their external validity and performance remain uncertain, limiting clinical applicability. This study aimed to externally validate and compare the performance of contemporary IE-specific and generic cardiac surgery (EuroSCORE II) risk scores in a large single-center cohort. Methods: Eighteen operative IE-specific risk scores, along with EuroSCORE II, were retrospectively applied to a database of 689 patients undergoing cardiac surgery for IE. Discrimination was evaluated using the area under the receiver operating characteristic curve (AUC), while calibration was assessed using the Hosmer-Lemeshow test, Brier score, and calibration slopes/intercepts. For each score, the type of validation reported in the original study was critically examined, noting that validation was not always performed. Additionally, the inclusion of IE-specific variables, such as pathogen type and valvular complications, was assessed to evaluate the reliability and clinical applicability of each score. Results: Among the 689 patients, 30% were female, with a median age of 69 years. The most frequent pathogens were Streptococcus (26%), Staphylococcus aureus (18%), coagulase-negative staphylococci (18%), and Enterococcus faecalis (16%). Operative mortality was 10.6% (n = 73). The RISK-E score showed the highest discrimination (AUC: 0.742), followed by APORTEI (0.734) and modified MELD-XI (0.730). All scores demonstrated good calibration, with scaled Brier scores above 0.8. Scores incorporating IE-specific variables generally performed better, while several widely used generic scores, including EuroSCORE II, overestimated operative risk. External validation revealed lower AUCs for many scores compared to original reports, highlighting the importance of rigorous evaluation. Conclusion: The RISK-E score demonstrated the highest discriminative ability and satisfactory calibration for predicting operative mortality in patients undergoing surgery for infective endocarditis. These results support the role of externally validated, IE-specific prognostic tools in guiding clinical assessment and selecting appropriate perioperative strategies.