Beta adrenergic blockade in hypertension: Practical and theoretical implications of long-term hemodynamic variations

Abstract

The effectiveness of propranolol, used alone, in reducing arterial pressure was reevaluated in 52 hypertensive patients (42 with essential and 10 with renovascular hypertension) with special regard to the hemodynamic basis for patient selection and the relation of variations in cardiac output to control of blood pressure. Repeated hemodynamic studies were performed before and during chronic treatment with propranolol, and in all the efficacy of beta adrenergic blockade was demonstrated by inhibition of chronotropic response to infusion of isoproterenol. Four patients discontinued propranolol because of side effects; among the rest, arterial pressure was reduced in 26 and unchanged in 22. There was no difference in responsiveness between subjects with essential and renovascular hypertension. Arterial pressure responses could not be predicted from hemodynamic values before treatment; although increased cardiac output was more frequent among responders than among nonresponders (59 vs. 37 percent), group averages were not significantly different. Treatment reduced cardiac output in both groups, so that effect on arterial pressure was related to changes in total peripheral resistance (r = 0.737, P <0.001) not to changes in output (r = 0.067). Thus, the hypertensive effect of propranolol seemed to imply a long-term adaptation of peripheral resistance to chronic reduction of output. The prolonged follow-up and repeat studies allowed a hemodynamic characterization of the occasional hypertensive responses to office visits and investigative procedures. These transient responses were not prevented during treatment although their hemodynamic basis was altered so that they were always related to increased peripheral resistance. Used in combination with other antihypertensive agents (12 patients), administration of propranolol nearly always controlled any tachycardia due to or persisting despite the other drugs and often improved the response of blood pressure.