T2-Weighted Imaging to Assess Post-Infarct Myocardium at Risk

TO UNDERSTAND THE AMOUNT OF SALVAGED MYOCARDIUM AFTER reperfusion of acute myocardial infarction (MI), it is essential to know the area of myocardium at risk (AAR) before reperfusion to assess salvaged myocardium as AAR minus final infarct size. Measuring myocardial salvage offers tremendous potential for development of novel pharmacologic agents that can reduce reperfusion injury and thereby increase myocardial salvage in reperfused MI. In animal studies, dyes such as phthalocyanine blue injected directly into the coronary circulation have been used to assess AAR. In humans, contrast echocardiography has been used in the catheterization lab before reperfusion to make this measurement (1). Although accurate and useful, this technology is available in very few laboratories around the world on a moment's notice when a patient presents with an MI. A technique to measure AAR in MI that could be applied after reperfusion would be ideal. T2-weighted (72-W) imaging by cardiac magnetic resonance (CMR) seems to be just such a technique, as demonstrated in the studies presented here in the iForum piece by Matthias Friedrich, MD. T2-weighted imaging is sensitive to myocardial edema, and it is thought that the area of edema can mark the original AAR. T2-weighted imaging was first applied in the mid-1990s, but it is only in the last few years that it has begun to hit its clinical stride.