Abstract 10938: Outcomes of Coronary Artery Bypass Grafting in 1.9 Million Medicare Patients From 1999-2010

Abstract

Introduction: Coronary artery bypass grafting (CABG) remains a mainstay of treatment in patients with coronary artery disease. Outcomes of CABG from a large modern U.S. cohort (the Medicare database) were analyzed, with a focus on outcomes. Methods: Medicare patients undergoing CABG from 1999-2010 were assessed. ICD-9 and CPT codes were used to describe operative details. Survival distributions were estimated with the Kaplan-Meier method, and compared with an age-/sex-/race-matched general US population cohort. A Cox proportional hazards analysis determined variables associated with survival. Cubic-spline analyses were used to assess hospital and surgeon volume-outcome relationships. Results: Median survival following CABG for the entire cohort (n=1,902,315) was 9.43 years (95% confidence intervals [CI] 9.41-9.45) (Figure 1A), and was 10.02 years (95% CI: 10.00-10.04) in isolated CABG (n=1,523,529) recipients (Figure 1B). During the 12 year study period, Medicare patients underwent CABG at 1,391 U.S. hospitals and by 5,899 U.S. surgeons. Multivariable analysis identified multiple predictors of death including age, gender, race, patient comorbidities, prior cardiac surgery, year of operation, adjunct cardiac procedures (e.g. valve repair/replacement or aortic repair), the lack of internal mammary artery (IMA) use, the absence of billing for cardiopulmonary bypass, and both hospital and surgeon volume. A transition point was identified in the surgeon-volume and hospital-volume relationships suggesting a volume beyond which additional case numbers only improved outcomes minimally (Figures 1C/1D). Conclusions: Survival following CABG in Medicare patients is robust. Even in this elderly cohort, the use of a single IMA was associated with significantly improved outcomes, and bilateral IMA use was associated with an even lower hazard for death compared with single IMA. Both hospital and surgeon volume had strong associations with survival.