Abnormalities in myocardial metabolism in patients with unstable angina as assessed by positron emission tomography

Abstract

Regional myocardial perfusion and glucose metabolism were assessed in six normal volunteers and 29 patients with coronary heart disease and stable or unstable angina using rubidium-82 (Rb-82) and F-18 fluoro 2-deoxy-D-glucose (FDG) with positron emission tomography. All normals and patients were studied following overnight fasting, at rest, with no angina or electrocardiographic signs of acute myocardial ischemia or necrosis. Rb-82 myocardial cross-sectional images were obtained employing the continuous infusion technique, while dynamic FDG imaging was employed after intravenous tracer bolus injection. Regional Rb-82 and FDG myocardial concentrations were then calculated by drawing regions of interest over the interventricular septum, anterior and lateral wall of the left ventricle. The mean Rb-82 uptake for each left ventricular region analyzed was found to be similar between both groups of patients and normal volunteers. The mean myocardial glucose utilization was found to be similar in normal volunteers and patients with stable angina (0.023 +/- 0.032 vs. 0.012 +/- 0.008 microns ml/min p less than 0.42). However, myocardial glucose utilization was found to be significantly higher in patients with unstable angina compared with both normals and patients with stable angina (0.048 +/- 0.047 microM/ml/min p less than 0.001 for both comparisons). Thus, in patients with severe coronary artery disease and unstable angina, myocardial glucose utilization was enhanced in spite of the absence of clinical, electrocardiographic, or detectable perfusion evidence of acute ischemia.