Distinction of salvaged and infarcted myocardium within the ischaemic area-at-risk with T2 mapping

Abstract

Aim: Area-at-risk(AAR)measurements often relyon T2-weighted images, but subtle differences inT2may be overlooked with this method. To determine the differences in oedema between salvaged and infarcted myocardium, we performed quantitative T2 mapping of the AAR. We also aimed to determine the impact of reperfusion time on T2 in the AAR. Methods: Twenty-two dogs underwent 2 h of coronary occlusion followed by 4 or 48 h of reperfusion before cardiac magnetic resonance imaging at 1.5 T. Late gadolinium enhancement images were used to define the infarcted, salvaged, and remote myocardium. T2 values from T2 maps and signal intensities on T2-weighted images were measured in the corresponding areas. Results: At both imaging time points, the T2 of the salvaged myocardiumwas longer than of remote (66.0±6.9 vs. 51.4±3.5 ms, P < 0.001 at4 h, and 56.7±7.3 vs. 48.1±3.5 ms, P < 0.001 at48 h). TheT2 was also longer in the infarcted myocardium compared with remote at both 4 and 48 h (71.4±7.6 ms, P< 0.01 vs. salvage and 64.0±6.9 ms, P = 0.03 vs. salvage, both P < 0.001 vs. remote). The increase in T2 in the salvaged myocardium compared with remotewas greater after 4 h than after 48 h (14.7±5.6 vs. 8.7±5.1 ms, P = 0.02). Conclusions: T2 relaxation parameters are different in the infarcted and salvaged myocardium, and both are significantly longer than remote. Furthermore, the magnitude of increase in T2 was less in the salvaged myocardium after longer reperfusion, indicating partial resolution of oedema in the first 48 h after reperfusion.