Acute Myocardial Infarction: Gd-DTPA Enhanced Magnetic Resonance Imaging

Abstract

This study was undertaken to determine the value of gadolinium dimeglumine (Gd-DTPA) enhanced MRI in the diagnosis of acute myocardial infarction. Seven cats were subjected to 2 hours of left anterior descending coronary arteryocclusion (group 1) and 8 cats to 1 hour of occlusion (group 2). Reperfusion was followed by taking Tl-weighted MR images at 5, 15, 30, 45, 60 minutes after Gd-DTPA (0.2 mmol/kg) injection. Myocardial enhancement patterns were categorized into three zones (central ischemic, peripheral ischemic, and normal) or two zones (ischemic and normal) and the presence of injured myocardium in each zone was confirmed by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Signal intensity (SI) of each zone was evaluated relative to back muscle in regard to its chronological changes and difference among the zones. Group 1 displayed three zones of enhancement in 6 cats whereas 1 cat in group 1 and all in group 2 showed two zones of enhancement. Intermediate SI central zone was compatible but smaller than TTC nonstained area, and determined to be a persistently occlusive injury. High SI peripheral zone in group 1 and high SI ischemic zone in group 2 were stained and determined as reperfused injury although reversibility was not definite. The peak SI, occurring 15 minutes after Gd-DTPA injection, of 2.47±0.48 at peripheral zone was greater than that of 1.66±0.36 at central zone in group 1 and of 1.81±0.41 at ischemic zone in group 2 (p < 0.05). SI of injured myocardium increased more rapidly and decreased more gradually than that of normal myocardium. That the features of SI change with time in injured myocardium was compatible with the results of other studies using different contrast agents. Gd-DTPA enhanced MRI differentiated persistently occlusive injury as central intermediate SI, and reperfused injury as homogenous high SI, with the maximal contrast between the two at 15 minutes after contrast injection, thus indicating the value of Gd-DTPA enhanced MRI in the diagnosis of acute myocardial infarction.