Myocardial Assessment during Subacute Stage after Ischemia-Reperfusion: Gd-DTPA-polylysine Enhanced MR Imagingin Cats

PURPOSE: To investigate changes in the size and degree of signal enhancement of reperfused myocardium during the subacute stage of an ischemic episode, using Gd-DTPA-polylysine enhanced magnetic resonance imaging. MATERIALS AND METHODS: In six cats, the left anterior descending artery was occluded for 150 minutes, and this was followed by reperfusion. Contrast enhanced T1-weighted spin echo magnetic resonance imaging using gadolinium diethylene triamine penta acetic acid-polylysine (Gd-DTPA-polylysine) was performed on the 1st , 2nd, and 6th days of the reperfusion period. The size of ischemic myocardium was estimated each day on MR images by measuring the size of signal enhanced area and the degree of signal enhancement according to time was measured. After sacrificing the animals on day 6, the myocardial specimen was histochemically stained with 2,3,5-triphenyltetrazoliumchloride(TTC). RESULTS: Signal enhancement and the size of the ischemic myocardium, as seen on MR images,decreased linearly during the six days of the subacute stage. On the 6th day, however, signal intensity was still higher than that of normal myocardium, and the size of signal enhanced area measured on MR images was significantly larger than on TTC-stained specimens (p<0.001). CONCLUSION: We conclude that the size of enhanced area and degree of signal enhancement decreased linearly during the subacute stage of reperfused myocardialinfarction and that the area of MR signal enhancement during the acute stage includes both irreversibly andreversibly damaged myocardium.