Studies from the early 1990s have documented greater intensity of treatment for patients with acute myocardial infarction (AMI) in the United States compared with Canada, with little difference in health outcomes. Little is known about whether treatments and outcomes are changing differently over time in the two countries, and whether the differences vary with patient age.
We conducted a retrospective cohort study of trends in cardiac procedure use, mortality, and recurrent AMI for patients 65 years or older hospitalized with AMI in the United States and Quebec. We examined Medicare claims and enrollment data from the United States (1.5 million) and provincial claims data from Quebec (35,000) between 1988 and 1994.
Use of cardiac procedures grew more rapidly between 1988 and 1994 in the United States, particularly for patients 75 years or older; unlike in Quebec, these cardiac procedures were performed soon after AMI. Both countries experienced significant declines in 1-year mortality: the decline averaged 1.27% points per year in the United States and 1.05% points in Quebec (P = ns). For AMI patients 75 years or older, 30-day and 1-year mortality declined approximately twice as rapidly in the United States as in Quebec (P < 0.01). The decline in mortality in the United States relative to Canada was significantly greater among patients 75 years or older but not among those age 65 to 74 years. Readmission rates with recurrent AMI were almost unchanged.
Over time, the use of cardiac procedures in elderly patients with AMI has risen more rapidly in the United States than in Quebec. These differences in procedure trends were associated with reductions in overall long-term AMI mortality in both countries.
Key words: Acute myocardial infarction; elderly; mortality; catheterization; angioplasty; coronary artery bypass surgery; population studies; trend analysis