Occlusive and reperfused myocardial infarcts: effect of Gd-DTPA on ECG-gated MR imaging.

In vivo magnetic resonance (MR) imaging was performed to determine the effect of gadolinium-DTPA on MR intensity and relaxation times of occlusive and reperfused acute myocardial infarcts. In 18 dogs the left anterior descending (LAD) coronary artery was ligated. Five hours after LAD artery occlusion, six dogs in group 1 received intravenous Gd-DTPA, 0.5 mmol/kg, and 6 dogs in group 2 received 0.1 mmol/kg. The myocardia of the remaining six dogs (group 3) were reperfused after 1 hour of coronary artery occlusion; these dogs received 0.1 mmol/kg Gd-DTPA intravenously 5 hours later. MR imaging was performed before (control) and 5 minutes after Gd-DTPA administration. Intravenous administration of 0.1 mmol/kg Gd-DTPA significantly improved contrast between infarcted and normal myocardium on T1-weighted spin echo images in group 3. In all groups, T2-weighted precontrast images provided contrast between infarcted and normal myocardium equivalent or better than that provided by T1-weighted postcontrast images. Thus, Gd-DTPA did not improve contrast between ischemically injured and normal myocardium in the early hours after coronary artery occlusion.