Serial myocardial scintigraphy after a single dose of thallium-201 in men after acute myocardial infarction

Serial myocardial scintigraphy after a single dose of thallium-201 in the period immediately after myocardial infarction may demonstrate redistribution of thallium-201 into perfusion defects that were evident in the initial scan. This study tested the hypothesis that evaluation of this redistribution, available within hours of infarction, could provide a more accurate estimate of the eventual perfusion defect than a single thallium-201 Image obtained immediately after infarction. The study group comprised 14 patients with a diagnosis on admission of probable acute myocardial infarction. The patients received thallium-201 a mean of 1.3 hours after admission to the coronary care unit. Imaging began 10 minutes after the thallium injection and was repeated 4 to 8 hours later.Eight patients with acute myocardial infarction had a definite reduction in one or more perfusion defects on serial scintigraphy, possibly indicating reperfusion of transiently Ischemic zones. Two patients with acute infarction had an increase in perfusion defects in a second study performed 6 hours after the initial scintigram. In the interval between scans, one patient had a cardiac arrest with clinical evidence of infarct extension after successful resuscitation; the other sustained a lateral extension of the infarct. One patient with acute aortic dissection had normal scans on both studies. All three patients with unstable angina had an abnormal initial scan; on repeat scan, the thallium-201 defect was unchanged in one patient, increased in one and decreased in the third. In the patients with myocardial infarction, repeat thallium-201 scans corresponded more nearly than the initial scans to the extent of technetilum-99m stannous pyrophosphate uptake by the heart.These data suggest that serial myocardial imaging with thallium-201 immediately after myocardial infarction can overcome some of the limitations of a single thallium-201 scintigram and may be useful in delineating ischemic from infarcted myocardium in the postinfarction period.