Detection of Viability of Dysfunctional Myocardium in Coronary Heart Disease. I. Radionuclide Imaging

Abstract

The question of myocardial viability in the presence of severe regional or global left ventricular dysfunction in patients with coronary artery disease poses a formidable challenge to the clinician. If the dysfunctional myocardium is viable, revascularization procedures are associated with improved contractile function, whereas no benefits are expected if the myocardium is nonviable. Thus, assessment of myocardial viability is necessary before optimal decisions can be made regarding the use of bypass surgery, angioplasty, or cardiac transplantation in a timely and cost-effective manner. The most reliable methods to detect viable myocardium include myocardial metabolic imaging of exogenous glucose utilization using ⊃18 F-FDG in combination with myocardial perfusion/flow studies, assessment of the integrity of the oxidative metabolism using ⊃11 C-acetate, and measurement of regional blood flow using ⊃13 N-ammonia or ⊃15 O-water. However, the equipment and expertise necessary to perform positron emission tomography (PET) are expensive and not generally available. Fortunately, alternative imaging modalities using routine radionuclide and echocardiographic techniques are widely available and have nearly the same accuracy as PET metabolic imaging. Excellent alternatives include perfusion imaging with ⊃201 thallium using the stress-redistribution-reinjection or the rest-redistribution protocols, or ⊃99m technetium sestamibi using a rest-delayed imaging protocol. As old techniques are being refined and new methods developed, such as metabolic imaging using SPECT techniques that utilize ⊃18 F-FDG or fatty acids labeled with ⊃131 I, the challenge is to choose the most appropriate technique after a critical review of the institutional resources and the merits and weaknesses of the technique.