Time course of 99mTc(Sn)-tetracycline uptake in experimental acute myocardial infarction

The relative concentration of 99mTc(Sn)-tetracycline in infarcted myocardium was determined as a function of time after coronary artery occlusion in mongrel dogs. The concentration ratio (infarct-to-normal myocardium) was highest within the first 2 days after occlusion (6.7 +/- 0.5 at 1 day and 8.0 +/- 1.6 at 2 days). By 1 week after occlusion the ratio had fallen to 1.9 +/- 0.2. In the region of infarction, the concentration of 99mTc(Sn)-tetracycline was homogeneously distributed across the inner three-quraters of the myocardial wall; the outer quarter of the wall had substantially lower concentrations during the first 5 days after infarction. The present study confirms the observation suggested in initial investigations in man that scintigraphy performed with 99mTc(Sn)-tetracycline will distinguish between acute and chronic myocardial infarctions.