Prolonged metabolic recovery allows late identification of ischemia in the absence of electrocardiographic and perfusion changes in patients with exertional angina.

Regional myocardial perfusion and exogenous glucose uptake were assessed in 10 normal subjects and 10 patients with coronary artery disease and stable angina pectoris using 82Rubiduim and 18F-2-fluoro-2-deoxyglucose with positron emission tomography. At rest regional myocardial perfusion and glucose uptake in patients were comparable with those in normals. In 7 patients and 5 normals a supine bicycle exercise test was performed within the positron camera. In all 7 patients, exercise induced typical chest pain and ischemic electrocardiographic changes accompanied by regional abnormalities of myocardial perfusion which normalized 5 to 14 minutes after the end of exercise. In these patients 18F-2-fluoro-2-deoxyglucose was injected during recovery from exercise when all the parameters that were altered during the test, including myocardial perfusion, were back to control. In all 7, glucose uptake in the regions which showed abnormal perfusion during exercise was significantly higher than in the non ischemic regions (i.e. the ones with a normal increment of 82Rubidium uptake during exercise). In 2 patients the test was repeated on a different day and 18F-2-fluoro-2-deoxyglucose was injected during exercise in the presence of frank ischemia. In contrast to the injection following exercise, in both patients, glucose uptake in the ischemic region was found to be lower than in the non ischemic ones. In conclusion, in patients recovering from exercise-induced ischemia exogenous glucose utilization is enhanced in the previously ischemic myocardium. This occurs in the absence of symptoms and electrocardiographic changes and allows the identification and location of previous myocardial ischemia.