Congenital Heart Surgery Program Variable Case Mix: Risk Associated With Adjusted Mortality Rate

Abstract

BackgroundCongenital heart operations are categorized into risk categories based on The Society of Thoracic Surgeons–European Association of Cardio-Thoracic Surgery Congenital Heart Surgery (STAT) Mortality Categories. The adjusted mortality rate should adjust for case mix. MethodsThe Society of Thoracic Surgeons Congenital Heart Surgery Public Reporting data were extracted for the top 50 U.S. News & World Report Cardiology and Heart Surgery Programs in 2021 (operations from January 2015 to December 2018). Variability in STAT 1 as a percentage of total operations and as a ratio to STAT 4+5 operations was evaluated. ResultsSTAT 1 cases varied between centers from 18% to 37% of total. The ratio of STAT 1 to STAT 4+5 varied from 0.52 to 1.97. There was an inverse relationship between the STAT 1:STAT 4+5 ratio and adjusted mortality rate that did not reach statistical significance (P = .12). When programs (n = 12) in the quartiles with the highest vs lowest STAT 1:STAT 4+5 ratio were compared, a significant difference was found in the median adjusted mortality rate (2.2% vs 2.95%, P = .03). ConclusionsThere is a 4-fold difference in the ratio of STAT 1 to STAT 4+5 cases among congenital heart surgery programs, even when smaller programs are excluded, suggesting significant differences in the decision-making philosophy. Programs with the highest proportion of STAT 1 cases had lower adjusted mortality rate, suggesting that The Society of Thoracic Surgery Congenital Heart Surgery Database mortality risk model adjusts well but not completely for case-mix variability between programs.