Sex differences in hospital risk-adjusted mortality rates for Medicare beneficiaries undergoing CABG surgery

Abstract

Background: The primary purpose of this study was to rank US hospitals performing coronary artery bypass graft (CABG) surgery on Medicare beneficiaries into 4 performance tiers and determine if there were overall and sex-specific differences in the risk-adjusted mortality rates across performance tiers.

Methods: A retrospective analysis was done using a Medicare Provider Analysis and Review (MEDPAR) file of all Medicare beneficiaries who underwent CABG surgery without valve repair or replacement during fiscal years 2003 and 2004. Logistic regression models controlling for demographic characteristics, comorbidities, and cardiac risk factors were used to predict the probability of in-hospital mortality. Hospitals performing at least 52 CABG surgeries during a fiscal year (at least 17 female patients) were ranked into 4 tiers. Rankings were based on the number of lives saved, calculated as the expected number of risk-adjusted deaths minus the actual number of deaths in the hospital during each fiscal year.

Results: Average risk-adjusted mortality rate was stable and declining over the 2 years: 3.68% in 2003 and 3.61% in 2004. In 2004, the average risk-adjusted mortality rate ranged from 1.39% in tier 1 hospitals to 6.40% in tier 4 hospitals. The sex-specific mortality rate was consistently higher for women in all tiers, with the differential smallest (0.68%) in tier 1 hospitals and greatest (2.67%) in tier 4 hospitals.

Conclusion: The sex differential increases from top- to bottom-tier hospitals, suggesting female beneficiaries could benefit from having CABG performed at tier 1 hospitals.