Interinstitutional Comparison of Risk-Adjusted Mortality and Length of Stay in Congenital Heart Surgery

Abstract

Risk Adjustment for Congenital Heart Surgery (RACHS) and basic Aristotle scores (BCS) have been shown to correlate with mortality and length of stay (LOS) after congenital heart surgery. Interinstitutional comparisons using these scores, as well as comprehensive Aristotle score (CCS), have not been demonstrated. We recorded age, weight, RACHS, BCS, CCS, mortality, and LOS for 1,103 patients undergoing cardiac surgery between September 1, 2004, and June 1, 2007, at two institutions. We used binary logistic and multiple linear regressions to evaluate determinants of mortality and LOS, respectively, the C statistic to compare the predictive power of the three scoring systems for mortality, the odds ratio to compare the two institutions, and regression coefficients to compare scoring systems and institutions for LOS. Raw mortality was 2.9% at both institutions. Final logistic regression models contained only CCS. Odds ratios for death at institutions 1 and 2 were 1.25 and 1.26, respectively (not significant). C statistics for RACHS, BCS, and CCS were 0.73, 0.63, and 0.81, respectively (p = 0.01 for CCS versus BCS; p = 0.02 for CCS versus RACHS). Final regression model for LOS retained age, RACHS, and CCS (R(2) = 0.44). The RACHS regression coefficient was greater for institution 2. The CCS tends to have more predictive power than RACHS and BCS for mortality. The LOS is moderately correlated with CCS, RACHS, and age together, but the model is a poor predictor of individual LOS. The LOS for RACHS category 6 cases differed between the institutions. This study suggests methods that can be used to compare institutions in a risk-adjusted manner.