Mortality Prediction After Cardiac Surgery in Children: An STS Congenital Heart Surgery Database Analysis

The Society of Thoracic Surgeons (STS) Congenital Heart Surgery Database (CHSD) provides risk-adjusted operative mortality rates to approximately 120 North American congenital heart centers. Optimal case-mix adjustment methods for operative mortality risk prediction in this population remain unclear.

A panel created diagnosis-procedure combinations of encounters in the CHSD. Models for operative mortality using the new diagnosis-procedure categories, procedure-specific risk factors, and syndromes or abnormalities included in the CHSD were estimated using Bayesian additive regression trees and least absolute shrinkage and selector operator (lasso) models. Performance of the new models was compared with the current STS CHSD risk model.

Of 98 825 operative encounters (69 063 training; 29 762 testing), 2818 (2.85%) STS-defined operative mortalities were observed. Differences in sensitivity, specificity, and true and false positive predicted values were negligible across models. Calibration for mortality predictions at the higher end of risk from the lasso and Bayesian additive regression trees models was better than predictions from the STS CHSD model, likely because of the new models' inclusion of diagnosis-palliative procedure variables affecting <1% of patients overall but accounting for 27% of mortalities. Model discrimination varied across models for high-risk procedures, hospital volume, and hospitals.

Overall performance of the new models did not differ meaningfully from the STS CHSD risk model. Adding procedure-specific risk factors and allowing diagnosis to modify predicted risk for palliative operations may augment model performance for very high-risk surgical procedures. Given the importance of risk adjustment in estimating hospital quality, a comparative assessment of surgical program quality evaluations using the different models is warranted.