Myocardial viability: Magnetic resonance assessment of functional reserve and tissue characterization

The determination of myocardial viability is crucial in patients with left ventricular dysfunction resulting from acute myocardial ischemia or chronic coronary artery disease. Viable myocardium will most likely benefit from r evascularization procedures. However, the revascularization of scar tissue will not lead to improvement of ventricular function and furthermore bears unnecessary risk for the patient. Currently, echocardiographic and radionuc lide techniques are the most established methods for the assessment of pres ence and extent of viable myocardium. Magnetic resonance imaging (MRI) also provides multiple approaches for determining viability of acute ischemical ly injured and hibernating myocardium. MRI can assess contractile reserve i n a manner similar to echo cardiography. Additionally, contrast-enhanced MR I can characterize myocardial ischemic injury, including the ability to dis criminate viable from nonviable zones. Several new contrast media have been introduced for this purpose. This review addresses the progress toward the goal of defining myocardial viability based on MR techniques and focuses o n the current and future role of MR in the assessment of viable myocardium.