Demarcation of myocardial ischemia: magnetic susceptibility effect of contrast medium in MR imaging.

Dysprosium diethylenetriamine-pentaacetic acid-bis (methylamide) (DTPA-BMA), a new nonionic contrast medium for magnetic resonance (MR) imaging, produces signal loss on T2-weighted images because of induced magnetic field gradients. The potential of this agent to delineate myocardial ischemia was investigated in 10 rats with acute (30 minutes) occlusion of the left coronary artery. T2-weighted MR images were acquired before and for 1 hour after intravenous administration of 1 mmol/kg of Dy-DTPA-BMA. Before administration of the contrast medium, signal intensity (SI) in the ischemic region was significantly greater than that in the normal myocardium; however, the borders of the ischemic region were not consistently distinct. The contrast medium caused marked decrease in SI of normal myocardium (18% +/- 3% of the control value), only slight decrease in the jeopardized region (76% +/- 6% of the control value), and no discernible effects on heart rate or blood pressure. Substantial contrast between normal and ischemic myocardium persisted for 1 hour. Moderate signal loss was observed in skeletal muscle. Dy-DTPA-BMA has the potential to demarcate the myocardial area in jeopardy as a region of high signal intensity because it erases signal preferentially in the normal myocardium.