Irreversibly damaged myocardium at MR imaging with a necrotic tissue-specific contrast agent in a cat model

PURPOSE: To investigate the capability of a necrosis-avid magnetic resonanc e (MR) contrast agent, bis-gadolinium mesoporphyrins, for assessment of irr eversibly damaged myocardium and to evaluate the time course of signal enha ncement in the reperfused myocardium. MATERIALS AND METHODS: Nine cats were subjected to 90 minutes of occlusion of the left anterior descending coronary artery followed by 90 minutes of r eperfusion. Contrast material-enhanced T1-weighted spin-echo images were ob tained for 12 hours in five cats and 6 hours in four cats. Pathologic exami nations of the resected specimens were performed with 2'3'5-triphenyl tetra zolium chloride (TTC) histochemical staining and electron microscopy. The s ize of enhanced area on MR images was compared with that of irreversibly da maged myocardium with TTC staining. The time course of signal enhancement w as evaluated. RESULTS: The size of enhanced area on MR images was well correlated with th at of irreversibly damaged myocardium with TTC staining. Maximum enhancemen t occurred 1-3 hours after administration of the contrast material, with me an enhancement of 171% that of normal myocardium. Electron microscopic exam inations showed severe myocardial damage in the irreversibly damaged myocar dium but only mild edematous changes in the reversibly damaged myocardium. CONCLUSION: MR images enhanced with bis-gadolinium mesoporphyrins provide a ccurate sizing of irreversibly damaged myocardium with a strong and persist ent signal enhancement in the reperfused myocardium.