Comparative prognostic value of dipyridamole-thallium-201 myocardial perfusion imaging 1-4 days after myocardial infarction versus routine predischarge submaximal exercise testing

We have previously demonstrated that infarct zone thallium-201 redistribution on dipyridamole-thallium-201 imaging performed 1-4 days after infarction predicts in-hospital and late cardiac events. The present study compared the prognostic value of 1- to 4-day postinfarction dipyridamole-thallium-201 imaging to routine predischarge submaximal exercise electrocardiography in 45 patients. Infarct zone thallium-201 redistribution was present in 14 patients. One patient had redistribution both outside and within the infarct zone. Submaximal exercise electrocardiography was positive for ischemia in 5 patients. The frequency of positive stress test results was significantly lower than infarct zone thallium-201 redistribution (p < 0.05). Cardiac events occurred in 5 patients during a 28 (± 11)-month follow-up: 1 cardiac death, 1 nonfatal myocardial infarction, 3 unstable angina requiring emergent revascularization. Cardiac events occurred more frequently in patients with infarct zone thallium-201 redistribution (5/14; 36%) than in patients without redistribution (0/31; p < 0.005). The frequency of cardiac events in patients with positive submaximal exercise electrocardiography (0/5) was not significantly different compared to that in patients with negative tests (5/40; 13%). The sensitivity for detecting patients at risk for late cardiac events was greater with the early dipyridamole-thallium-201 imaging (5/5) than with predischarge submaximal exercise testing (0/5; p < 0.01). Thus, dipyridamole-thallium-201 myocardial imaging appears to be superior to submaximal exercise electrocardiography for risk stratification after myocardial infarction, not only because it can be applied earlier in hospitalization to allow earlier management decisions, but also because it has greater sensitivity and predictive value for identifying patients at risk for future late cardiac events.