Propranolol in Patients with Angina Pectoris

Abstract

The effect of propranolol, which reduces coronary blood flow, in angina pectoris was assessed in a double-blind crossover study of 19 patients with coronary artery disease documented by positive exercise tests and coronary angiography. The patients received placebo and propranolol (160 mg per day)[long dash]in random fashion. Exercise tolerance (to anginal pain) was measured by a treadmill test, during which heart rate, blood pressure, and ecg were monitored. Seventeen of the 19 patients had fewer episodes of pain (62% reduction for group as a whole), 14 used fewer nitroglycerine tablets (65% reduction for group), and 15 had greater exercise tolerance (22% average increase) while taking propranolol than they did while taking placebo. Fifteen of the 19 patients were significantly improved by propranolol, which reduced resting and exercise heard rate and decreasdd exercise blood pressure. When myocardial O2 requirement is estimated by the product of blood pressure X heart rate, propranolol diminished the O2 requirement in all cases, the average decrease being 27%. Propranolol failed to increase significantly the amount of work done to the point of ST depression. The probable mechanism by which propranolol alleviates angina pectoris is a reduction in myocardial O2 requirements. The failure of propranolol to alter favorably the exercise ecgs suggests that the reduction in myocardial O2 requirements is offset by an equivalent reduction in myocardial O2 supply and raises the question as to whether propranolol is really beneficial in angina pectoris.