Electrophysiological effects of acebutolol

Abstract

We administered acebutolol, a partially cardioselective beta-adrenergic blocking agent with membrane stabilising properties, to 11 patients with coronary artery disease but no evidence of conduction system disease. Electrophysiological studies and serial plasma concentration determinations were made before and after infusion of acebutolol, 1.0 mg/kg, over 15 minutes. At 25 minutes after initiation of the infusion, mean heart rate decreased from 77±5 to 68±3 (SEM) beats/min (P<0.005). Systolic blood pressure fell by 10 mmHg (P<0.02). AH interval rose from 110±8 to 137±15 ms (P<0.02). The atrioventricular node functional refractory period increased from 447±29 ms to 471±30 ms (P<0.07). The HV interval increase, from 46±2 to 51±2 ms, was not significant. The sinus node recovery time and atrial effective refractory period were inconsistently affected. The mean plasma concentration of acebutolol at 25 minutes was 957±92 ng/ml. Four patients (group 1) had concentrations above 1000 ng/ml (mean 1280±113 ng/ml), and the other 7 (group 2) had concentrations below 1000 ng/ml (mean 774±55 ng/ml). The mean HV interval increased in group 1 patients from 44±2 ms to 52±3 ms. This change was significantly different from the negligible change in HV interval in the group 2 patients. In addition, the increase in AH interval was much greater in group 1 patients. We conclude that, like propranolol, acebutolol reduces heart rate and blood pressure, and slows conduction and increases refractoriness in the atrioventricular node. Acebutolol also slows His-Purkinje conduction at higher plasma concentrations.