Temporal changes in the outcomes of acute myocardial infarction in Ontario, 1992-1996

Abstract

Background: There is relatively little information available on recent population-based trends in the outcomes of patients who have had an acute myocardial infarction (AMI). We, therefore, conducted a study of temporal trends in the outcomes of AMI patients in Ontario, Canada, between the 1992 and 1996 fiscal years.

Methods: 114,618 AMI patients were discharged from hospitals in Ontario between Apr. 1, 1992, and Mar. 31, 1997. After specific exclusion criteria were applied the final sample of 89,456 patients was divided into 5 cohorts according to the fiscal year of discharge. As part of the Ontario Myocardial Infarction Database project the linked administrative data pertaining to these patients were used to examine cohort characteristics, cardiac procedures used and mortality rates for each of the 5 cohorts over time.

Results: There was a significant increase in the percentage of patients in Ontario receiving coronary angiography, percutaneous transluminal coronary angioplasty and coronary artery bypass grafting surgery (p < 0.001) after an AMI between 1992 and 1996. In addition, the overall 30-day risk-adjusted mortality rate declined from 15.5% in 1992 to 14.0% in 1996 (p = 0.001) and the 1-year risk-adjusted mortality rate declined from 23.7% in 1992 to 22.3% in 1996 (p = 0.017). Virtually all of the improvement occurred within 30 days of admission. The absolute decline in 1-year mortality rates was significant for patients under the age of 65 (2.3%, 95% confidence interval [CI] 1.4% to 3.2%) and for males (1.2%, 95% CI 0.2% to 2.2%); absolute declines were not significant for patients 65 years of age or older (0.7%, 95% CI -0.6% to 2.0%) and for female patients (-0.1%, 95% CI -1.7% to 1.5%). Interestingly, post-infarction coronary angiography and coronary artery bypass grafting rates were consistently lower in the older and the female patients throughout the study period.

Interpretation: There was a modest improvement in the short- and long-term survival of patients in Ontario after an AMI between 1992 and 1996. The Ontario experience suggests that recent advances in AMI management have been of more benefit to younger and male AMI patients.