Assessment of myocardial viability in chronic ischemic heart disease: current status

Assessment of myocardial viability is clinically important in the work-up of patients with ischemic cardiomyopathy. Numerous studies in the past 2 decades demonstrated that revascularization improves left ventricular ejection fraction (LVEF), heart failure symptoms and prognosis in patients with viable myocardium. Conversely patients without viable tissue do not benefit from revascularization. Also, a substantial amount of viable myocardium (at least 25% of the left ventricle) is needed to result in improvement of LVEF. Hence, both identification and quantification of the extent of viable myocardium are required for a careful selection of candidates for revascularization. Indeed, the presence of a substantial amount of viable myocardium decreases the risk of surgery in patients with reduced LVEF. Several diagnostic techniques are available to identify myocardial viability. Positron emission tomography (PET), myocardial perfusion imaging, and stress echocardiography are considered the traditional techniques to evaluate myocardial viability. Recently, newer techniques including cardiac magnetic resonance (CMR), myocardial contrast echocardiography (MCE) and electromechanical mapping have been introduced. In this manuscript the status of the currently available techniques to assess viability was reviewed. Also the relative merits of each technique for prediction of functional recovery and prognosis was addressed. The available retrospective data support the clinical use of viability assessment. Patients with ischemic cardiomyopathy should undergo viability testing to determine therapeutic strategy. In the presence of substantial amount of viable myocardium, patients should undergo revascularization since benefits in terms of left ventricular function, remodeling, symptoms and prognosis may be anticipated. However, prospective randomized trial are needed to confirm these data.