Early assessment of myocardial contractility by contrast-enhanced magnetic resonance (ceMRI) imaging after revascularization in acute myocardial infarction (AMI)

Backgroud: Recent studies have demonstrated that the size and shape of the hyperenhanced areas on contrast-enhanced magnetic resonance imaging (ceMRI) were nearly identical to areas of irreversible injury, as defined by histochemical staining. We compared the transmural extent of infarct (TEI), as defined by ceMRI, to the initial ECG findings for acute myocardial infarction (AMI), and we also assessed functional contractility according to TEI. Methods: 12 patients who presented with their first myocardial infarction underwent cine and ceMRI 4 weeks later after their successful revascularization. TEI and wall thickening were determined by using a 30-segment model. Results: Infarction was observed in 81 (23.9%) segments, of which 46 segments (56.8%) had abnormal wall motion and 35 segments (43.2%) had normal wall motion. Of the 35 segments, 33 (94.3%) had subendocardial infarction. 17 segments had infarct of less than 25% of the wall thickness, and all of them had normal wall motion. On the other hand, 11 segments had infarct of more than 75% of wall thickness, of which 11 (100%) had abnormal wall motion. None of segments with nearly transmural infarction were observed in non ST-elevation AMI. The majority of the segments with infarct had non-transmural infarction (87.5%), even if the segments were in ST-elevation AMI (76.1%). Infarct size, as defined by ceMRI, was strongly correlated with peak CK-MB and Troponin-T (r=0.96, p<0.001, r=0.91, p<0.001, respectively). Conclusion: TEI defined by ceMRI is inversely related to the contractility after revascularization in AMI. We were able to predict the future contractile function of segments with infarction using ceMRI before revascularization.