Coronary artery bypass grafting in Canada: national and provincial mortality trends, 1992-1995

Abstract

Background: Despite a body of research on outcomes of coronary artery bypass grafting (CABG) in Canada, little is known about Canada-wide outcome trends and interregional differences in outcome. The objectives of this study were to examine Canadian trends in rates of in-hospital death after CABG and to compare provincial risk-adjusted death rates.

Methods: Hospital discharge data were obtained from the Canadian Institute for Health Information and were used to identify complete cohorts of patients who underwent CABG in 8 provinces in fiscal years 1992/93 through 1995/96. Data from Quebec hospitals were not available. A logistic regression model was used to calculate risk-adjusted death rates by year, province, and province and year.

Results: A total of 50,357 CABG cases were studied, with an overall death rate of 3.6%. A national trend of decreasing mortality was found, with a risk-adjusted death rate of 3.8% in 1992/93 versus 3.2% in 1995/96 (relative decrease of 17%) (p < 0.001 for difference across years). Some provinces (e.g., Alberta, Manitoba and Ontario) achieved overall declines in death rates over the study period, whereas others (e.g., British Columbia and Saskatchewan) did not. The average severity of illness of patients who underwent CABG differed considerably across provinces. Despite risk adjustment for these differences, provincial death rates varied significantly (p < 0.001).

Interpretation: Rates of death after CABG in Canada decreased significantly in a relatively short period. Despite this encouraging finding, there were interprovincial differences in severity of illness and risk-adjusted death rates. This finding raises the possibility of unequal access to CABG and variable quality of care for patients undergoing the surgery across Canadian provinces.