Trends in Patient Characteristics and Outcomes of Coronary Artery Bypass Grafting in the 2000 to 2012 Medicare Population

Background. The purpose of this analysis was to examine the trends in patient characteristics and outcomes in patients who underwent coronary artery bypass grafting (CABG) over a 12-year period in the Medicare database. Methods. The study included 1,264,265 isolated CABG procedures in the Medicare population from January 2000 through November 2012. Comorbidities were determined using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnostic codes. Trends in patient characteristics and hospital outcomes were assessed with Cochran-Armitage trend tests. Long-term survival was examined with Kaplan-Meier survival curves. Results. The median age was 74 years. Comorbidity profiles increased significantly over time. The number of patients undergoing CABG decreased from 131,385 in 2000 to 71,086 in 2012. The majority of patients underwent multivessel revascularization (13.5% single-vessel CABG, 35.2% 2-vessel CABG, 32.1% 3-vessel CABG, and 15.7% ≥4-vessel CABG). The percentage of patients undergoing 1- and 2-vessel revascularization increased over time, whereas that of ≥3-vessel CABG decreased. Single internal mammary artery (IMA) use increased from 75.6% to 88.6%. Median length of stay (LOS) was 8 days. Thirty-day mortality decreased from 4.2% to 3.0%. Hospital mortality fell from 4.0% in 2000 to 2.7% in 2012 (odds ratio [OR], 0.73; 95% confidence interval [CI], 0.69-0.77). Survival was 93% at 6 months, 91% at 1 year, 84% at 3 years, and 76% at 5 years. Five-year survival changed little over time (range, 75%-77%). Conclusions. Despite rising comorbidities in Medicare patients undergoing CABG, hospital mortality fell significantly from 2000 to 2012. When adjusted for comorbidities, this signified a 27% reduction in hospital mortality. IMA use increased during the study period, and there was a trend of decreased use of 3 or more grafts.