Myocardial Metabolic Imaging in the Clinical Setting

Abstract

Glucose and free fatty acids are a major energy source in the myocardium. Metabolic imaging with single photon emission tomography (SPECT) and positron emission tomography (PET) have been widely used for the evaluation of the pathophysiology of coronary artery disease (CAD) and heart failure. 18F fluorodeoxyglucose (FDG) is a glucose analogue that is used to measure myocardial glucose utilisation. The myocardial uptake of a modified branched fatty acid, 15-(p-[iodine-123] iodophenyl)-3-(R,S) methylpentadecanoic acid (BMIPP), reflects the activation of fatty-acid metabolism by co-enzyme A (CoA) and indirectly reflects cellular adenosine triphosphate (ATP) production. The turnover rate of the tricarboxylic acid (TCA) cycle reflects the rate of overall myocardial oxidative metabolism. 11C acetate is readily metabolised to CO2 almost exclusively through the TCA cycle. These three major agents have been most commonly used for probing myocardial energy metabolism in vivo. Such metabolic imaging has been used for assessing myocardial viability on the basis of persistent glucose utilisation in ischaemic but viable myocardium. BMIPP and FDG have been identified for locating a recent history of myocardial ischaemia. Furthermore, metabolic imaging is promising for the assessment of the pathophysiology of heart failure and the treatment effect of various drugs, as well as mechanical treatments. In this article we will provide an overview of the application of myocardial metabolic imaging in a clinical setting.