In-hospital mortality risk assessment in elective and non-elective cardiac surgery: a comparison between EuroSCORE II and age, creatinine, ejection fraction score

Age, creatinine, ejection fraction (ACEF) score is a simplified algorithm for prediction of mortality after elective cardiac surgery. Although mainly conceived for elective cardiac surgery, no information is available on its performance in non-elective surgery and on comparison with the new EuroSCORE II. This study was undertaken to compare the performance of ACEF score and EuroSCORE II within classes of urgency. Complete data on 13 871 consecutive patients who underwent major cardiac surgery in a 6-year period were retrieved from three prospective institutional databases. Discriminatory power was assessed using the c-index and h with Delong, bootstrap and Venkatraman methods. Calibration was evaluated with calibration curves and associated statistics. The in-hospital mortality rate was 2.5%. The discriminatory power of ACEF score within elective and non-elective surgery was similar (area under the curve (AUC) 0.71, 95% confidence interval (CI) 0.67-0.74 and AUC 0.68, 95% CI 0.62-0.73, respectively) but significantly lower than that of EuroSCORE II (AUC 0.80, 95% CI 0.77-0.83 for elective surgery; AUC 0.82, 95% CI 0.78-0.85 for non-elective surgery). The calibration patterns were different in the two subgroups, but the summary statistics underscored a miscalibration in both of them (U-statistic and Spiegelhalter Z-test P-values < 0.05). Even the calibration of EuroSCORE II was insufficient, although it was demonstrated to be well calibrated in the first tertile of predicted risk. This study demonstrated that the performance of ACEF score in predicting in-hospital mortality in elective and non-elective cardiac surgery is comparable. Nonetheless, it is not as satisfactory as the new EuroSCORE II, as its discrimination is significantly lower and it is also miscalibrated.