Assessment of Myocardial Viability by Magnetic Resonance Imaging Techniques

Abstract

In contrast to the well established scintigraphic methods such as single photon emission computed tomography (SPECT) and positron emission tomography (PET), which are routinely used in the assessment of myocardial viability, magnetic resonance (MR) imaging and MR spectroscopy techniques have only recently been applied to address these questions. Due to its excellent spatial resolution MR imaging is well suited for the exact assessment of morphological and functional changes after myocardial infarction.1–5 A chronic, transmural myocardial infarct, e.g. a myocardial infarct which is older than 16 weeks, is in general characterized by a significant reduction in wall thickness.6–8 In contrast, a chronic myocardial infarct with hibernating myocardium will show less wall thinning, although wall motion may be severely impaired in both conditions. Therefore, measurement of wall thickness alone may provide important information about the presence of clinically relevant amounts of residual viable myocardium. An acute transmural myocardial infarct without residual viability may or may not yet exhibit a significant reduction in wall thickness. Assessment of myocardial wall thickness in acute myocardial infarcts will therefore not be helpful to distinguish between viable and scarred myocardium. This problem may be overcome by MR spectroscopy techniques, which detect key molecules (ATP, phosphocreatine) of the metabolic pathways, in an area of acute or subacute myocardial infarcts.9