Invited Review Magnetic Resonance Imaging for the Assessment of Myocardial Viability Louise E.J. Thomson, MB ChB, Raymond J. Kim, MD, Robert M. Judd, PhD * The identification of myocardial viability in the setting of left ventricular (LV) dysfunction is crucial for the prediction of functional recovery following revascularization. Al- though echocardiography, positron emission tomography (PET), and nuclear imaging have validated roles, recent advances in cardiac magnetic resonance (CMR) technology and availability have led to increased experience in CMR for identification of myocardial viability. CMR has unique ad- vantages in the ability of magnetic resonance spectroscopy (MRS) to measure subcellular components of myocardium, and in the image resolution of magnetic resonance proton imaging. As a result of excellent image resolution and ad- vances in pulse sequences and coil technology, magnetic resonance imaging (MRI) can be used to identify the trans- mural extent of myocardial infarction (MI) in vivo for the first time. This review of the role of CMR in myocardial viability imaging describes the acute and chronic settings of ventricular dysfunction and concepts regarding the un- derlying pathophysiology. Recent advances in MRS and MRI are discussed, including the potential for dobutamine MRI to identify viable myocardium and a detailed review of the technique of delayed gadolinium (Gd) contrast hyper- enhancement for visualization of viable and nonviable myo- cardium. Key Words: MRI; spectroscopy; viability; gadolinium hy- perenhancement; myocardium J. Magn. Reson. Imaging 2004;19:771–788. © 2004 Wiley-Liss, Inc. IN THE LAST FIVE years, there have been multiple tech- nological advances in noninvasive cardiac imaging that are now being translated into new clinical options for the diagnosis and management of cardiac disease. Echocar- diography, nuclear imaging, computed tomography (CT), and magnetic resonance imaging (MRI) have established and emerging roles in noninvasive cardiac imaging. Of the clinical applications for cardiac imaging, assessment of cardiac viability has experienced significant growth as a reflection of the rising number of patients with coronary artery disease (CAD)–related left ventricular (LV) dysfunc- tion (1). Despite its relatively recent addition to the cardiac imaging armory, cardiac magnetic resonance (CMR) via- bility imaging has established a clinical role and is serving to provide new insights into the natural history of myo- cardial damage and myocardial dysfunction in patients with CAD. CMR can provide morphological, functional (MRI) and metabolic (magnetic resonance spectroscopy, MRS) information about the heart, and offers detailed viability information that cannot be obtained from any other modality. Throughout the Western world there has been a decline in the number of deaths from myocardial infarction MI) but a dramatic increase in the incidence of congestive cardiac failure. In the United States between 1970 and 2000, cardiovascular disease death rates decreased over- all by 50%, however mortality rates for congestive heart failure more than doubled and hospitalizations for con- gestive heart failure more than tripled (1). Palliative treat- ment options for heart failure are numerous (2), however the ideal treatment is the restoration of myocardial sys- tolic function through revascularization of dysfunctional but viable ischemic myocardium. There is general agreement that viable chronically hypoperfused myocardium should be revascularized and that nonviable myocardium will not recover sys- tolic function with revascularization. Delaying revascu- larization in patients with viable myocardium is asso- ciated with increased mortality (3). There is, additionally, a weight of observational evidence that revascularization in patients with severe myocardial dysfunction in whom there is no significant viability may be associated with increased risk compared to medical therapy (4,5). Hence, there is a need to identify the presence and extent of viable and nonviable myo- cardium in order to determine appropriate therapy for the individual. Revascularization (when appropriate) must be expedited, as there is a limited time frame in which chronically ischemic myocardium will remain vi- able before irreversible damage occurs (6). DEFINING VIABLE AND NONVIABLE MYOCARDIUM. By definition, viability is continued cell life. A myocyte is viable while alive and nonviable once irreversible cellu- Duke Cardiovascular Magnetic Resonance Center, Duke University, Durham, North Carolina. Contract grant sponsor: National Heart Foundation of New Zealand; Contract grant sponsor: NIH-NHLBI; Contract grant numbers: R01- HL63268, K02-HL04394, R01-HL64726. *Address reprint requests to: R.M.J., Duke Cardiovascular Magnetic Resonance Center, Duke University Health System, P.O. Box 3934, Durham, NC, 27710. E-mail: Robert.Judd@dcmrc.mc.duke.edu Received August 22, 2003; Accepted March 1, 2004. DOI 10.1002/jmri.20075 Published online in Wiley InterScience (www.interscience.wiley.com). JOURNAL OF MAGNETIC RESONANCE IMAGING 19:771–788 (2004) © 2004 Wiley-Liss, Inc. 771