Regional myocardial glucose metabolism in angina pectoris obtained from positron emission tomography

This article presents a review of studies carried out with positron tomography on myocardial blood flow and glucose metabolism in patients with coronary artery disease and either stable (SA) or unstable angina (UA) pectoris. Regional blood flow was assessed with rubidium 82, an analogue of potassium, and glucose metabolism both with fluorine 18-labeled fluorodeoxyglucose (FDG) and carbon 11-labeled glucose (CG). There were no clear differences in regional myocardial blood flow between SA and UA patients and a group of normal volunteers. FDG uptake was low and homogeneous in both SA patients and normals. In contrast, all UA patients showed abnormally high FDG uptake in at least one left ventricular region at rest in the absence of symptoms or signs of acute ischemia. In the recovery from a period of exercise-induced angina, FDG uptake in SA patients was observed to be higher in previously ischemic regions than in nonischemic regions (as defined by 82Rb). It is postulated that higher FDG uptake in the postischemic myocardium of SA patients is due to repletion of glycogen stores. It remains unclear whether the high uptake in UA patients is due to a recent ischemic episode or is a reflection of a chronic adaptation to repeated stress.