Mode of Action of Beta Blockers in Angina Pectoris

Abstract

Research Laboratories, AB Hässle, Fack, S-431 20 Mölndal, Sweden The therapeutic effect of beta adrenoceptor blockers in angina pectoris can be ascribed to an inhibition of β1 receptor mediated stimulation of heart rate and myocardial contractility, resulting in an improved oxygen supply-demand balance in the myocardium. When given in equipotent β1 blocking doses, the nonselective blocker propranolol and the β1 selective blocker metoprolol differ markedly as regards inhibition of adrenaline induced β2 mediated vasodilatation. Only propranolol will inhibit this effect. After propranolol, adrenaline therefore elicits a haemodynamic effect pattern characterized by high peripheral vascular resistance, high arterial blood pressure, low cardiac output and increased cardiac size. In view of these findings it is suggested that a β1 selective blocker may be a more efficient antianginal agent than a nonselective blocker in those patients in which the anginal attack is associated with a significant release of adrenaline. The clinical relevance of this hypothesis has not been tested.