Assessment of myocardial viability in chronic left ventricular dysfunction

Differentiation of infarcted from viable myocardium is of critical clinical importance in patients with severely impaired left ventricular function. While positron emission tomography is considered the 'gold- standard' morality for detection of viable myocardium, expense has limited its more widespread use. Therefore, many centers employ surrogate tests for metabolic viability. Various imaging protocols involving thallium-201 are currently used to establish myocardial viability. In several recent studies, low-dose dobutamine echocardiography has been useful in predicting recovery of poorly contractile myocardium. Myocardial contrast echocardiography is a promising new technique which may predict viability by defining areas of preserved microvascular integrity. The clinical role of these diagnostic moralities in the setting of depressed ventricular function is as yet uncertain. Clarification of the utility of these tests should allow more judicious selection of patients who would derive the greatest survival benefit from revascularization procedures.