Imaging to distinguish between viable and nonviable myocardium: Pathophysiologic basis and importance of positron emission tomography

One goal of strategies designed to restore nutritive perfusion in patients with left ventricular dysfunction attributable to coronary artery disease is salvage of reversibly ischemic myocardium in an effort to improve patients' left ventricular function, signs and symptoms, and survival. Accurate identification of patients likely to benefit from interventions such as coronary revascularization requires the differentiation of viable (reversibly dysfunctional) myocardium from nonviable (persistently dysfunctional) tissue. To date, no consensus has been reached regarding the best approach for achieving this differentiation. In this review, the pathophysiologic characteristics of viable and nonviable myocardium are summarized, and diagnostic methods that exploit these characteristics for the purposes of detecting viable myocardium are discussed. Emphasis is placed on approaches that use positron emission tomography because of its usefulness in quantifying those specific metabolic processes that support both tissue viability and the capacity for functional recovery.