Objectives: We sought to compare U.S. and Canada's post-myocardial infarction (MI) cardiac catheterization practices in the detection of severe coronary artery disease (CAD).
Background: Little is known about the efficiency with which the aggressive post-MI catheterization strategy observed in the U.S. detects severe CAD compared with the more conservative strategy observed in Canada.
Methods: From the U.S. and Canadian patients who had participated in the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Arteries trial (n = 22,280, 11.5% Canadian), we examined the frequency of in-hospital cardiac catheterization, the prevalence of severe CAD observed at catheterization (diagnostic efficiency) and the total number of MI patients with severe CAD identified (diagnostic yield).
Results: The rate of catheterization in the U.S. was more than 2.5 times that in Canada (71% vs. 27%, respectively, p < 0.001). With identical prevalences of severe CAD at catheterization (17%) in the two countries, the higher frequency of catheterization in the U.S. resulted in the identification of more than two and a half times as many cases of severe CAD compared with Canada (12 severe CAD cases identified per 100 post-MI patients in the U.S., vs. 4.6 per 100 in Canada). If considered in isolation, we estimated that these differences in severe disease detection might effect a small long-term survival advantage in favor of the U.S. strategy (estimated 5.0 lives saved per 1,000 MI patients).
Conclusions: Canada's more restrictive post-MI cardiac catheterization strategy is no more efficient in identifying severe CAD than the aggressive U.S. strategy, and may fail to identify a substantial number of post-MI patients with high risk coronary anatomy. The long-term impact of these differences in practice patterns requires further evaluation.