Coronary artery bypass grafting in Canada: hospital mortality rates, 1992-1995

Rates of in-hospital death after coronary artery bypass grafting (CABG) have been studied in many regions of Canada as possible indicators of hospital-specific quality of care. This nationwide study examined observed and risk-adjusted death rates for 23 Canadian hospitals performing CABG.

Hospital discharge data were obtained from the Canadian Institute for Health Information and were used to identify all CABG procedures performed in Canadian hospitals in fiscal years 1992/93 through 1995/96. Cases from Quebec hospitals were not studied because hospitals in that province do not report to the institute. Observed death rates were evaluated, and a logistic regression model was used to calculate a risk-adjusted death rate for each hospital for the 4-year period studied. Changes over time in hospital-specific death rates were also examined.

A total of 50,357 CABG cases were studied, with an overall death rate of 3.6%. Interhospital comparisons showed that average severity of illness varied considerably across hospitals. Despite risk adjustment accounting for this variable severity, there was considerable variation in adjusted death rates across the 23 hospitals, from 1.95% to 5.76% (p < 0.001 for difference across hospitals). For some hospitals, death rates decreased between 1992/93 and 1995/96, whereas for others the rates were stable or increased.

Risk-adjusted rates of in-hospital death after CABG vary widely across Canadian hospitals. There may be differences in quality of care across hospitals, and focused quality-improvement initiatives may be necessary in some institutions.