Abstract P314: The Impact of Hospital Cardiac Specialization on Outcomes After Coronary Artery Bypass Graft Surgery: Analysis of Medicare Claims Data

Abstract

Background Hospital volume has been widely embraced as a proxy for hospital quality; little attention has been focused on an alternative quality metric - hospital specialization. While specialization occurs on a continuum, prior studies of specialization have largely focused on a small number of highly specialized ( specialty) hospitals. Studies on the broad relationship between hospital specialization and outcomes after cardiac surgery are lacking. Methods We used Medicare data to identify 705084 patients who underwent CABG at 1130 hospitals during 2001-2005. We stratified hospitals into quintiles of cardiac specialization based on the relative proportion of all Medicare discharges at each hospital classified as Major Disease Category 5 - diseases of cardiovascular system. We obtained hospital characteristics from the 2001-2005 AHA survey. We used multivariable hierarchical regression to examine the association of cardiac specialization with risk of 30-day mortality adjusting for patient characteristics & CABG volume. Results The mean age of CABG recipients was 75 years, 65% were men, 92% were white. Patient demographic & comorbidity was generally similar between quintiles of hospital specialization. The median cardiac specialization was 29.7% for all hospitals (mean cardiac specialization in lowest quintile of hospital specialization was 23.2% vs. 45.2% for highest quintile). Compared to the highest quintile, hospitals in the lowest quintile had fewer beds (296 vs. 314, p < .01), were less likely to be teaching hospitals (22% vs. 26%, p < .01) and had lower CABG volume (63 vs. 239, p < .01). They also admitted less transfer patients (8.3% vs. 17.5%, p < .01) and performed less concurrent valve surgery (13% vs. 15%, p < .01). Unadjusted 30-day mortality was higher at least specialized hospitals compared to most specialized hospitals (4.9% vs. 4.3%, p < .01). Odds of mortality remained higher at these hospitals after adjustment for patient characteristics (OR 1.15 95% CI [1.07 - 1.24] p trend < .01) but was similar after further adjustment for CABG volume (OR 1.05 95% CI [0.97 - 1.15] p trend 0.65). Conclusion After accounting for hospital volume, hospitals with greater cardiac specialization did not have better CABG outcomes than less specialized hospitals.