Early detection of myocardial infarction with magnetic resonance imaging in a canine model.

Abstract

To determine the effectiveness of magnetic resonance imaging in detecting early myocardial infarction in vivo after coronary artery occlusion. A prospective, controlled canine study using a left anterior descending coronary artery ligation model. After thiopental anesthesia, nine mongrel dogs underwent cardiac-gated magnetic resonance imaging with a 2.35-T magnet with a 40-cm bore before and four hours after ligation of the left anterior descending coronary artery. Hemodynamic and left ventricular blood flow changes were determined. The mean image intensity ratio of the suspected infarct region to the normal myocardium was determined in the four-hour postocclusion images and compared with the ratio from the same anatomic region obtained at baseline. The area of necrotic and ischemic myocardium was determined using fluorescein and triphenyl tetrazolium chloride staining immediately after four-hour images. All animals were noted to have necrotic (range, 1.8% to 20.4% of ventricles) and ischemic (range, 9.2% to 36.6% of ventricles) myocardium with histochemical staining. The mean intensity ratio of infarcted myocardium four hours after left anterior descending coronary artery occlusion was significantly higher than baseline (four hours, 2.31 +/- 0.82; baseline, 1.02 +/- 0.09; P < .002). Magnetic resonance imaging can distinguish myocardial edema associated with acute infarcting myocardium in vivo as early as four hours after left anterior descending coronary artery occlusion. Magnetic resonance imaging may be clinically useful in identifying thrombolytic therapy candidates among acute myocardial infarction patients presenting with atypical symptoms.