Noninvasive measurements of infarct size after thrombolysis with a necrosis-avid MRI contrast agent

Background-Gadophrin-2 is a new MRI contrast agent with high affinity for n ecrotic myocardium. The aim of the study was to evaluate whether noninvasiv e measurements of infarct size after thrombolysis are possible with gadophr in-2-enhanced MRI. Methods and Results-Coronary artery thrombosis was induced in 3 groups of d ogs by the copper-coil technique, Thrombolytic therapy together with aspiri n and heparin was initiated after 90 minutes of occlusion. One day (group A ), 2 days (group B), or 6 days (group C) after infarction, gadophrin-2 was injected intravenously (50 mu mol . kg(-1)). In vivo T1-weighted segmented turbo-FLASH, in vivo T2-weighted segmented half-Fourier turbo spin echo (HA STE), and T1- and T2-weighted spin-echo MRI of the excised heart were perfo rmed 24 hours after gadophrin-2 injection. Regions of strong enhancement we re observed on T1-weighted images. Planimetry of short-axis MR images and o f corresponding triphenyltetrazolium chloride (TTC)-stained left ventricula r (LV) slices showed a close correlation between the enhanced areas and TTC -negative areas for both in vivo (r(2)=0.98, P<0.0001; mean difference, 0.9 +/-2.0% [SD] of the LV volume [LVV]) and postmortem (r(2)=0.99, P<0.0001; m ean difference, 0.9+/-1.4% of LVV) measurements. T2-weighted images overest imated the infarct size by 8.1+/-5.4% of LVV. The mean infarct size was 10. 8+/-11.6% of LW (group A), 22.4+/-11.7% (group B), and 5.1+/-9.3% (group C) . Conclusions-In this animal model, in vivo gadophrin-2-enhanced MRI could pr ecisely determine infarct size after thrombolytic therapy. This technique m ay be very useful for the noninvasive evaluation of infarct size after repe rfusion for AMI.