Background and hypothesis: Ischemic complications occur frequently during hospitalization after acute myocardial infarction. Dipyridamole-thallium scintigraphy performed early after admission can detect residual ischemia, may have additional prognostic value and be useful in the management of these patients.
Methods: Dipyridamole infusion and 201thallium imaging were performed on the third day of infarction in 114 consecutive patients. Coronary angiography was performed before hospital discharge in 90% of patients and exercise testing was performed at the time of discharge in patients without contraindications.
Results: Side effects occurred in 28 patients, but they were mild and transient or rapidly reversed with intravenous aminophylline. During hospitalization, three patients died and four had a nonfatal reinfarction. Patients with these major cardiac events had previously shown a higher prevalence of reversible perfusion defects during testing (71 vs. 31%, p < 0.05). In addition, 19 patients had early recurrent ischemia requiring early in-hospital revascularization. Overall, cardiac events defined as death, reinfarction, or early myocardial revascularization occurred in 22 patients. Of the patients with these events, 68% had thallium redistribution on initial myocardial scanning compared with 25% of patients without events (p = 0.0001). Patients with cardiac events also showed a higher number of myocardial segments with reversible perfusion defects (1.8 +/- 2.2 vs. 0.6 +/- 1.3, p = 0.001). Logistic regression analysis revealed that among all the other clinical, scintigraphic, and angiographic variables, the presence of thallium redistribution on the dipyridamole-thallium scan was the only independent predictor of cardiac events, increasing the risk by sixfold. Furthermore, during a 1-year follow-up, 14 other patients had ischemic events. Of these, 64% had previously shown thallium redistribution during early dipyridamole testing compared with 19% of patients without cardiac events (p < 0.001).
Conclusions: Intravenous dipyridamole-thallium-scintigraphy performed very early after myocardial infarction is safe and useful to predict in-hospital ischemic events.