EFFECTS OF EPINEPHRINE INFUSION ON CHEST PAIN IN SYNDROME-X IN THE ABSENCE OF SIGNS OF MYOCARDIAL-ISCHEMIA

Eight female patients (aged 51 to 65 years) with New York Heart Associ ation class II angina pectoris, normal coronary angiograms, normal hyp erventilation, and abnormal exercise stress tests (chest pain and ST d epression), and 5 sex- and age-matched controls participated in this s tudy. Epinephrine was given intravenously to both patients and control s at 5-minute intervals in doses of 0.1, 0.2, 0.3, 0.4, and 0.6 nmol/k g/min. After rest(15 minutes), the alpha-adrenoceptor antagonist phent olamine or placebo was administered intravenously to patients in a dou ble-blind, crossover study on 2 separate occasions in doses of 250 mu g/min for 5 minutes and 500 mu g/min for the next 10 minutes; the epin ephrine infusion was repeated. Blood pressure, heart rate, and electro cardiogram were monitored continuously and pain was estimated on the B org CR-10 scale. On a third occasion, chest pain was induced in patien ts using the same epinephrine protocol during echocardiographic monito ring. In the control group, all patients received the maximal epinephr ine dose. No chest discomfort or pain developed. In the patient group, the maximal tolerable epinephrine dose (0.39 +/- 0.19 nmol/kg/min) de creased diastolic pressure (-14 +/- 9 mm Hg, p <0.01) and increased he art rate (+24 +/- 10 beats/min, p <0.01), not statistically different from the control group. Pulse pressure increased in the patient group (27 +/- 17 mm Hg, p <0.01) but not in the controls. Left ventricular e lection fraction at baseline was within reference limits (58% to 75%) and did not change during epinephrine infusion. Chest pain, which was not different in quality, intensity, or location from the patient's ha bitual angina-like pain, was induced in 7 of the 8 patients, 4 of whom endured only a moderate dose of epinephrine. No ST depressions were o bserved. After administration of phentolamine, chest pain developed to a degree to that with epinephrine alone. Chest pain is induced by epi nephrine infusion in patients with syndrome X. Because no signs of isc hemia occurred, a hypersensitive afferent cardiac nervous system may b e an important cause of chest pain.