Effects of propranolol on exercise tolerance in angina pectoris

Abstract

The effect of beta adrenergic blockade with propranolol in angina pectoris was investigated by means of a standardized exercise tolerance test. The parenteral dose needed to produce satisfactory blockade, as judged by bradycardia, was about one-tenth of that required in the case of pronethalol. No side effects were noted after intravenous injection. In a preliminary study of 20 patients, the exercise tolerance of the 7 patients who were limited by angina pectoris was generally increased after propranolol was injected. Five patients limited by angina in the control test had no angina at a similar work level after the drug. Seven patients were limited by fatigue and showed no change in exercise tolerance. To distinguish the response to propranolol from a nonspecific placebo effect, 14 patients, limited by angina in an initial test, after an inert injection and after propranolol, were studied. Five patients with severe angina showed some improvement in exercise tolerance. Nine patients with moderate angina showed a significant increase in exercise tolerance beyond that found after the placebo. These studies suggest that propranolol improves the exercise tolerance of some patients with angina pectoris. However, any improvement in myocardial oxygenation after beta blockade is probably produced at the expense of an impairment in myocardial contractility and a fall in peripheral blood flow. Propranolol should therefore be avoided in patients with evidence of left ventricular failure.