Predicted Risk of Mortality Score predicts 30-day readmission after coronary artery bypass grafting

Abstract

Objective: Quality metrics and reimbursement models focus on 30-day readmission rates after coronary artery bypass grafting (CABG). Certain preoperative variables are associated with higher rates of readmission. The purpose of this study was to determine whether STS Predicted Risk of Mortality (PROM) scores predict 30-day readmission following CABG.

Methods: A retrospective review of all patients undergoing isolated CABG between 2002 and 2017 at a US academic institution was performed. Logistic regression analysis was used to determine the association between PROM and 30-day readmission, and the area under the receiver-operator curve (ROC) was calculated to estimate predictive accuracy.

Results: During the study period, 21,719 patients underwent CABG and 2,023 (9.2%) were readmitted within 30 days. Readmitted patients were sicker with higher rates of comorbid conditions and higher STS PROM scores (1.03% vs 1.42%, GMR 1.33, CI 1.27-1.38, p < 0.0001). Median time to readmission was 8 days (IQR 4-15) with length of stay 5 days (4-6). By PROM quintile, higher PROM scores were associated with increased odds of readmission. PROM-adjusted 30-day mortality was higher in the readmitted group (1.04% vs 0.21%, OR 4.53, CI 2.67-7.69, p < 0.001), and mid-term survival was worse as well. PROM alone was a modest predictor of readmission (area under ROC 0.59, CI 0.57-0.60) compared to insurance status (0.55, 0.53-0.56), ejection fraction (0.52, 0.50-0.54), and history of heart failure (0.51, 0.50-0.52).

Conclusion: STS PROM scores are associated with increased risk of readmission following CABG.

Keywords: CABG; Readmission; STS PROM.