Differences in the Treatment of Myocardial Infarction in the United States and Canada

Abstract

To compare practice patterns and clinical outcomes for a costly yet common condition, acute myocardial infarction. Retrospective cohort study in two university hospitals (Stanford [Calif] University and McGill University, Montreal, Quebec) and a patient survey. All consecutive patients (n = 518) treated for acute myocardial infarction in the coronary care unit of those two hospitals over 2 years. Rates of diagnostic and therapeutic procedures, mortality, reinfarction, and level of functional status (by chart review and patient survey). Demographic and clinical characteristics were similar for the two groups. Noninvasive tests were more common at McGill (exercise tests, 56% vs 20%; tests of left ventricular function, 86% vs 59%; P < .0001 for both). In contrast, invasive procedures were more common at Stanford (angiography, 55% vs 34%; angioplasty, 30% vs 13%; and bypass surgery, 10% vs 4%; P < .0001). At a median follow-up of 20 months, reinfarction and mortality rates were similar at Stanford and McGill (13% vs 8% and 28% vs 27%, respectively; P > .05 for both). In contrast, the angina rate was slightly lower at Stanford (33% vs 40%; P = .15), and the functional status of Stanford patients was better than that of McGill patients (mean Duke Activity Status Index score, 28.8 and 22.9, respectively; P = .006). This functional status difference persisted after adjustment for differences in clinical factors, including coronary revascularization. The aggressive treatment of the American patients with myocardial infarction did not improve reinfarction and mortality rates compared with the conservative treatment of the Canadian patients. The superior functional status of the American patients merits further investigation.