Comprehensive Summary
This retrospective study described the development of an AI model that could identify key preoperative variables associated with failure to rescue (FTR) after coronary artery bypass grafting (CABG). FTR was defined as postoperative mortality within 30 days due to stroke, renal failure, reoperation, or prolonged ventilation. 9,974 patients from the STS institutional cardiac surgical base were selected, with an overall FTR rate of 2.5% among the population. Initially, 35 peroperative variables were selected based on prior literature, studies, and author expertise. Researchers used the RFECV model, a greedy search feature selection algorithm, to narrow down these variables to only key risk factors. For each variable, the model assigned a SHAP value, which indicated how much impact each variable had on the outcome (FTR). Of those variables, the model identified 12 key risk factors, with the most influential factors being low levels of hematocrit, ejection fraction, creatinine, and platelet count, as well as high levels of bilirubin, BMI, WBC count, age, hemoglobin A1c, and a high MELD score. Additionally, the model evaluated the effects risk factors had on each other; for example, high albumin and high hemoglobin levels were associated with strong positive P values, while low values of both caused more variability in prediction. The model’s predictive performance was analyzed using a random forest model, with the best precision-recall curve, calibration slope, and brier score reflecting the model’s relatively high predictive ability (0.78, 0.82, and 0.02, respectively).
Outcomes and Implications
Identification of key preoperative risk factors for CABG can potentially reduce FTR if patients take efforts to minimize those factors before the operation. Not only did this model identify key risk factors, it also analyzed the effects of interactions between variables, which may further enhance clinician’s awareness of risk factors to look for in prospective CABG patients. While this AI model displayed a high predictive ability, it should be noted that the model was only internally validated with a single dataset with a low percentage of FTR in the population. In the future, hospitals may replicate this model’s approach to identify risk factors unique to their own population datasets to better manage patient outcomes for at-risk patients.