Role of Hospital Volumes in Identifying Low-Performing and High-Performing Aortic and Mitral Valve Surgical Centers in the United States

Importance Identifying high-performing surgical valve centers with the best surgical outcomes is challenging. Hospital surgical volume is a frequently used surrogate for outcomes. However, its ability to distinguish low-performing and high-performing hospitals remains unknown. Objective To examine the association of hospital procedure volume with hospital performance for aortic and mitral valve (MV) surgical procedures. Design, Setting, and Participants Within an all-payer nationally representative data set of inpatient hospitalizations, this study identified 682 unique hospitals performing surgical aortic valve replacement (SAVR) and MV replacement and repair with or without coronary artery bypass grafting (CABG) between 2007 and 2011. Procedural outcomes were further assessed for a 10-year period (2005-2014) to assess representativeness of study period. Main Outcomes and Measures In-hospital risk-standardized mortality rate (RSMR) calculated using hierarchical models and an empirical bayesian approach with volume-based shrinkage that allowed for reliability adjustment. Results At 682 US hospitals, 70 295 SAVR, 19 913 MV replacement, and 17 037 MV repair procedures were performed between 2007 and 2011, with a median annual volume of 43 (interquartile range [IQR], 23-76) SAVR, 13 (IQR, 6-22) MV replacement, and 9 (IQR, 4-19) MV repair procedures. Of 225 SAVR hospitals in the highest-volume tertile, 34.7% and 36.0% were in the highest-RSMR tertile for SAVR + CABG and isolated SAVR procedures, respectively, while 21.5% and 17.5% of the 228 SAVR hospitals in the lowest-volume tertile were in the lowest respective RSMR tertile. Similarly, 36.8% and 43.5% of hospitals in the highest tertile of volume for MV replacement and repair, respectively, were in the corresponding highest-RSMR tertile, and 17.4% and 11.2% of the low-volume hospitals were in the lowest-RSMR tertile for MV replacement and repair, respectively. There was limited correlation between outcomes for SAVR and MV procedures at an institution. If solely volume-based tertiles were used to categorize hospitals for quality, 44.7% of all valve hospitals would be misclassified (as either low performing or high performing) when assessing performance based on tertiles of RSMR. Conclusions and Relevance Hospital procedure volume alone frequently misclassifies hospital performance with regard to risk-standardized outcomes after aortic and MV surgical procedures. Valve surgery quality improvement endeavors should focus on a more comprehensive assessment that includes risk-adjusted outcomes rather than hospital volume alone.