Advances in Magnetic Resonance Imaging of the Myocardial Area at Risk and Salvage.

Abstract

Cardiac magnetic resonance (CMR) imaging in survivors of acute ST-segment–elevation myocardial infarction (STEMI) provides accurate and precise measurements of left ventricular dimensions, and infarct pathologies are uniquely characterized. Acute coronary artery occlusion initiates a wavefront phenomenon of ischemia1 commencing from the endocardial layer and propagating radially toward the epicardium, and typically, myocardial infarction will supervene unless coronary reperfusion is achieved in a timely manner. The myocardial area at risk is the jeopardized perfusion territory of the culprit artery. See Article by Nordlund et al Ischemia results in an increase in myocardial water content manifesting as myocardial edema, and the local changes in T1 and T2 relaxation times (milliseconds) can be revealed by CMR.2 Myocardial salvage is calculated by subtracting the infarct size on contrast-enhanced CMR from the myocardial area at risk, revealed by T1- or T2-weighted CMR, and predicts the likelihood of functional recovery.2 On the contrary, edema imaging has limitations because the area at risk diminishes in size from ≈5 days post reperfusion,3,4 and T2 relaxation times within the ischemic zone vary as infarct pathologies evolve.5,6 Several CMR methods are now available for imaging myocardial edema7; the most established of which is the T2-weighted short tau inversion recovery (T2-STIR) black blood technique. This method has the advantage of being generically available across all major vendors. However, image quality may be limited when using T2-STIR CMR because of low contrast-to-noise ratio between normal and abnormal myocardium and a propensity for subendocardial bright rim …