NO CONTINUOUS RELATIONSHIP BETWEEN VETERANS AFFAIRS HOSPITAL CORONARY-ARTERY BYPASS-GRAFTING SURGICAL VOLUME AND OPERATIVE MORTALITY

Background. The purpose of this study was to determine whether risk-ad justed coronary artery bypass grafting mortality rates are significant ly related to coronary artery bypass grafting surgical procedure volum e within the Department of Veterans Affairs hospital system. Methods. From April 1987 to September 1992, expected mortality rates were calcu lated for 23,986 coronary artery bypass grafting procedures performed at 44 different Veterans Affairs hospitals. Results. This study found a statistically significant relationship between annual hospital coron ary artery bypass grafting volume and observed mortality rates (p < 0. 02). However, no statistically significant relationship between corona ry artery bypass grafting volume and risk-adjusted operative mortality was found (p = 0.10). Using analysis of variance on hospital-level da ta, hospitals with 100 or less cases per year have higher observed to expected mortality ratios than hospitals performing more than 100 case s per year (p = 0.03). Using Poisson regression models, however, a vol ume threshold could not be found. Conclusions. These findings are cons istent with the current Veterans Affairs policy requirements to period ically review quality at low-volume hospitals.