Occlusive myocardial infarction: Investigation of bis-gadolinium mesoporphyrins-enhanced T1-weighted MR imaging in a cat model

PURPOSE: To test whether bis-gadolinium mesoporphyrins-enhanced magnetic re sonance (MR) imaging can accurately depict irreversibly damaged myocardium in occlusive myocardial infarction. MATERIALS AND METHODS: Ten cats were subjected to 90 minutes of occlusion o f the left anterior descending coronary artery. Bis-gadolinium mesoporphyri ns-enhanced T1-weighted MR imaging was performed in the cats for 6 hours. H istopathologic examinations with 2 '3 '5-triphenyl tetrazolium chloride (TT C) staining and electron microscopy were performed on the resected specimen s. The time course and pattern of signal intensity enhancement were evaluat ed. The size of the infarcted myocardium was estimated on the MR images by measuring the size of the signal intensity-enhanced area. RESULTS: In eight of 10 cats, it was impossible to distinguish infarcted my ocardium from normal myocardium at visual inspection of T1-weighted MR imag es. The contrast ratio between infarcted and normal myocardium did not incr ease significantly over time. In one of the two remaining cats, a doughnut pattern of signal intensity enhancement was noted. The other cat showed int ensely homogeneous enhancement of infarcted myocardium at MR imaging. The s ize of the area of signal intensity enhancement at MR imaging in these two cats was accurately mapped to that of the infarction on the TTC-stained spe cimens. CONCLUSION: Occlusive myocardial infarction cannot be accurately detected a t bis-gadolinium mesoporphyrins-enhanced MR imaging.