Electrophysiologic effects of asocainol, a new antiarrhythmic agent with predominant class I action

In experiments on 6 mongrel dogs the electrophysiologic effects of the new antiarrhythmic compound (+/-)-6,7,8,9-tetrahydro-2,12-dimethoxy-7-methyl-6-phenethyl-5H- dibenz[d,f]azonin-1-ol (asocainol) were examined in the non-ischemic heart. The PR interval increased significantly following doses of 5 mg/kg caused by a conduction delay in the His-Purkinje system. At high doses (10 mg/kg) the QRS duration was also prolonged. Atrial and ventricular effective refractory periods were only slightly increased. Asocainol significantly increased the atrial fibrillation threshold, whereas the ventricular fibrillation threshold was not altered. Hemodynamics were not changed except for a slight increase in heart rate after 10 mg/kg asocainol. Thus asocainol predominantly exhibited class Ia antiarrhythmic properties, whereas calcium antagonistic actions could not be established in this intact dog heart model.