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Original Investigation
November 8, 2017

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

Author Affiliations
  • 1Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas
  • 2Division of Cardiovascular Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor
  • 3Department of Cardiovascular and Thoracic Surgery, University of Texas Southwestern Medical Center, Dallas
  • 4Division of Cardiology, Department of Medicine, Columbia University Medical Center, New York, New York
  • 5Associate Editor, JAMA Cardiology
  • 6Center for Heart & Vascular Health, Christiana Care Health System, Wilmington, Delaware
  • 7Brigham and Women’s Hospital Heart & Vascular Center, Harvard Medical School, Boston, Massachusetts
JAMA Cardiol. Published online November 8, 2017. doi:10.1001/jamacardio.2017.4003
Key Points

Question  Do procedure volumes accurately identify low-performing and high-performing aortic and mitral valve surgical centers in the United States?

Findings  In an all-payer data set consisting of 682 US hospitals performing aortic and mitral valve surgical procedures, volume was only modestly associated with in-hospital mortality. The use of volume-based tertiles to categorize hospitals for quality misclassified 305 of 682 valve hospitals as either low performing or high performing when assessing performance based on tertiles of in-hospital risk-standardized mortality rate.

Meaning  Hospital procedure volume alone frequently misclassifies hospital performance with regard to risk-standardized outcomes after aortic and mitral valve surgical procedures.

Abstract

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.

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