MRI of acute myocardial ischemia: Comparing a new contrast agent, Gd-DTPA-24-cascade-polymer, with Gd-DTPA

A new macromolecular contrast agent, gadoliniun diethylenetriamine pentaace tic acid (Gd-DTPA)-24-cascade-polymer, was compared with Gd-DTPA for time-d ependent delineation of acute myocardial ischemia, Acute myocardial ischemi a was produced in 12 rats by occluding the anterior branch of the left coro nary artery for 20-40 minutes, Dynamic spin-echo magnetic resonance imaging (MRI) was performed for 30 minutes after injection of Gd-DTPA (n = 6) or t he cascade polymer (n = 6) using equimolar doses (0.1 mmol of Gd/kg). The c ontrast agent-induced changes in signal intensity (Delta SI) in normal and Ischemic myocardium were observed, In normal myocardiun, both contrast agen ts caused a sharp increase in Delta SI, followed by a decline to baseline v alues over the 30-minute period. Enhancement in the ischemic myocardium was attenuated. Gd-DTPA showed greater Delta SI in ischemic myocardium than th e cascade polymer, which gave rise to virtually no enhancement, Significant differences (P < 0.05) in signal enhancement between normal and Ischemic m yocardium persisted for only 6 minutes using Gd-DTPA but for 18 minutes wit h the cascade polymer. Use of Gd-DTPA-24-cascade-polymer extends the tempor al window of dynamic contrast-enhanced MRI for the differentiation of Ische mic and normal myocardiun. Identification of the ischemic zone Is easier wi th the cascade polymer, which demonstrates virtually no signal enhancement in this territory, J, Magn, Reson, Imaging 1999;9:204-208, (C) 1999 Wiley-L iss, Inc.