Development and Validation of a Score to Predict the Risk of Readmission After Adult Cardiac Operations

Background: The purpose of this study was to develop and validate a risk score for readmissions after cardiac operations.

Methods: Adults surviving to discharge after cardiac operations at a single institution from 2008 to 2013 were randomly divided 3:1 into training and validation cohorts. The primary outcome was readmission within 30 days of discharge. A multivariable model was constructed in the training cohort incorporating variables associated with 30-day readmission in univariate logistic regression. Points were assigned to predictors in the multivariable model proportional to their odds ratios.

Results: Among 5,193 patients undergoing cardiac operations and surviving to discharge, the 30-day readmission rate was 10.3% (n = 537). The most common reasons for readmission were volume overload (24%; n = 131) and infection (21%; n = 113). The risk score incorporated 5 multivariable predictors and was out of 20 possible points. The predicted rate of 30-day readmission based on the training cohort ranged from 5.9% (score = 0) to 54.7% (score = 20). Patients were categorized as low (score = 0; readmission 5.7%), moderate (score 1-7; readmission 11.0%), and high risk (score >7; readmission 24.2%) (p < 0.001). Thirty-day readmission rates based on these score categories were similar in the validation cohort (low 6.4%, moderate 11.0%, high 17.4%; p < 0.001). There was a robust correlation between predicted rates of readmission in the training cohort based on the composite risk score and actual rates of readmission in the validation cohort (r = 0.95; p < 0.001).

Conclusions: We developed and validated a risk score for readmission after cardiac operations that may have utility in targeting interventions and modifying risk factors in high-risk populations.