The ACEF II Risk Score for cardiac surgery: updated but still parsimonious

The age, creatinine, and ejection fraction (ACEF) score was introduced in 2009 and is presently included in the guidelines for myocardial revascularization of the European Society of Cardiology and Association for Cardio-Thoracic Surgery as a risk stratification tool for surgical and percutaneous myocardial revascularization. The present study introduces an updated version of the ACEF (ACEF II) inclusive of emergency surgery and pre-operative anaemia. The development series includes 7011 consecutive cardiac surgery patients operated at a single institution. The validation series includes 1687 consecutive cardiac surgery patients operated in a different institution. The five factors included in the ACEF II were assessed in a multivariable logistic regression model testing their independent role as predictors of operative (in hospital or 30 days after surgery) mortality. Based on the odds ratio of each predictor, the ACEF II score is calculated as age(years)/ejection fraction (%). Additional points are attributed to a serum creatinine level > 2 mg/dL (2 points), emergency surgery (3 points) and anaemia [haematocrit (HCT) < 36%, 0.2 points per each HCT point below 36%]. The final model was well calibrated. Discrimination of the ACEF II (c-statistics 0.814) was significantly (P = 0.041) better than the ACEF (c-statistics 0.773) and equal to the EuroSCORE II. In the external validation, the ACEF II confirmed a better discrimination than the ACEF and good calibration properties. The ACEF II allows the inclusion of emergency patients and, through a re-modulation of the coefficients and the inclusion of anaemia, appears more adequate to the present cardiac surgery scenario.