Patients with normal coronary arteries who experience chest pain have constituted an enigma for many years. As some of these patients have ischemia-like ST segment depression in response to exercise stress testing attempts have been made to ascertain whether the syndrome has an ischemic etiology. Measurement of cardiac metabolite exchange in response to pacing stress is one of the methods used to investigate ischemia in these patients. Ischemia increases the myocardial carbohydrate-lipid utilization ratio and the change in cardiac lactate exchange from uptake to output, due to enhanced anaerobic glycolysis, has been the most frequently used metabolic index of ischemia. Despite that initial studies had demonstrated cardiac ischemia in patients with chest pain and normal coronary arteries, using metabolic markers, abnormal lactate findings in these patients have declined in recent studies. Thus, the findings of myocardial lactate production during stress in up to 40% of patients in the early studies have almost “vanished” in recent studies.