Objectives: We measured the uptake of technetium-99m tetrofosmin ((99m)Tc) and thallium-201 (201Tl) in areas of healed transmural myocardial infarction and in regions of acute peri-infarction ischemia. Methods: Anesthetised pigs with a 1-month old transmural infarction elicited by permanent ligature of the left anterior descending (LAD) coronary artery below the first branch underwent one hour of proximal LAD occlusion followed by injection of (99m)Tc-tetrofosmin and 201Tl either in the left atrium (GI, n = 19) or in the jugular vein (GII, n = 6). Twelve other pigs (GIII) with a similar acute peri-infarction ischemia received (99m)Tc-tetrofosmin and 201Tl into the left ventricle during cardiocirculatory arrest to rule out the effect of coronary collaterals. Radiotracer counting was determined in samples from normal, acute ischemic and necrotic regions. Results: Uptake of (99m)Tc-tetrofosmin and 201Tl was greater in the infarct scar (median % of normal tissue: 20 for (99m)Tc and 8.6 for 201Tl in GI; 22 and 15 in GII) than in acute ischemic myocardium (3.2 and 2.5 in GI; 6.4 and 3.3 in GII). Radiotracer injection in arrested hearts (GIII) depicted a similar pattern (median % of injected dose; 6.2 for (99m)Tc and 10 for 201Tl in the scar; 2,3 and 4,0 in acute ischemia; and 2.9 and 3.5 in normal tissue). The infarcted region showed connective tissue and lack of viable myocardium. Conclusions: A 1-month old infarct scar with no viable myocardial tissue can take up significant fractions of (99m)Tc-tetrofosmin and 201Tl even in the absence of coronary collateral perfusion. Data suggest that the infarct scar can extract these radiotracers from the intraventricular blood.
- Myocardial infarction
- Myocardial viability