In-hospital mortality following coronary artery bypass graft surgery in veterans health administration and private sector hospitals

OBJECTIVES. Compare severity-adjusted in-hospital mortality in patients undergoing coronary artery bypass graft surgery (CABG) in VA and private sector hospitals in two geographic regions. RESEARCH DESIGN. Retrospective Cohort Study. SUBJECTS. Consecutive male patients undergoing CABG from October 1993 to December 1996 in: 43 VA hospitals with cardiac surgery programs (n = 19,266); 32 hospitals in New York (NY) State (n = 44,247); and 10 hospitals in Northeast (NE) Ohio (n = 9696). METHODS. Demographic and clinical data were abstracted from medical records. Logistic regression analysis identified 10 independent patient-level predictors (P < 0.01) of in-hospital mortality: age, prior CABG, angioplasty before CABG, ejection fraction, diabetes, peripheral vascular disease, congestive heart failure (CHF), cerebrovascular disease, renal insufficiency, and chronic obstructive pulmonary disease (COPD). RESULTS. Unadjusted mortality was higher in VA patients than in NY or NE Ohio patients (3.5% vs. 2.0%, and 2.2%, respectively). Mortality decreased (P <0.001) with increasing volume (3.6% in low [<500 cases], 3.0% in moderate [500-1000 cases], and 2.0% in high [>1000 cases] volume hospitals). Median volume was lower in VA than private sector hospitals (410 vs. 1520), and no VA hospitals were classified as high volume. Adjusting for patient-level predictors and volume, the odds of death was higher in VA patients, relative to private sector patients (OR, 1.34; 95% CI, 1.11-1.63; P < 0.001). In stratified analyses, the odds of death in VA patients was similar in low volume hospitals (OR, 0.86; P = 0.39), but higher in moderate volume hospitals (OR, 1.50; P = 0.01). CONCLUSIONS. VA hospitals had lower CABG volume than private sector hospitals in NY and NE Ohio, and higher in-hospital mortality. However, the difference in mortality was limited to moderate-volume hospitals. These findings suggest that hospital volume is an important modifier in comparisons of CABG mortality in VA and private sector hospitals. The higher mortality in VA hospitals may, in part, be caused by differences in surgical capacity and patient demand that lead to lower volume cardiac surgery programs.