Thallium-201 myocardial scintigraphy in acute myocardial infarction and ischemia.

Thallium-201 scintigraphy provides a sensitive and reliable method of detecting acute myocardial infarction and ischemia when imaging is performed with understanding of the temporal characteristics and accuracy of the technique. The results of scintigraphy are related to the time interval between onset of symptoms and time of imaging. During the first 6 hr after chest pain almost all patients with acute myocardial infarction and approximately 50% of the patients with unstable angina will demonstrate 201TI perfusion defects. Delayed imaging at 2--4 hr will permit distinction between ischemia and infarction. In patients with acute myocardial infarction, the size of the perfusion defect accurately reflects the extent of the infarcted and/or jeopardized myocardium, which may be used for prognostic stratification. In view of the characteristics of 201TI scintigraphy, the most practical application of this technique is in patients in whom myocardial infarction has to be ruled out, and for early recognition of patients at high risk for complications.