Electrophysiologic effects of pindolol on atrioventricular conduction in canine heart

The effects of intravenous pindolol on the electrophysiologic properties of the atrioventricular conduction system was studied in intact dog, using His bundle electrogram and the extrastimulus method. Pindolol was administered intravenously in a dose range of 4 to 40 micrograms/Kg. The latter dosage of pindolol is above those used clinically. Significant effects of intravenous pindolol were observed on sinus cycle length, the A-V nodal conduction time, the ERP of the atrium, the ERP and FRP of the A-V node, and the ERP of the ventricle. Sinus cycle length was prolonged during sinus rhythm. Intraatrial conduction time was not altered by pindolol, while the ERP of the atrium was slightly increased. The A-H interval was generally prolonged by pindolol without Wenckebach type A-V block, but the H-V interval was unchanged. Both ERP and FRP of the A-V node was prolonged. The ERP and RRP of the His-Purkinje system were not statistically evaluated, because no block within the His-Purkinje system were not statistically evaluated, because no block with the His-Purkinje system or prolongation of H-V interval was produced and only a few QRS complexes by extrastimulus showed aberrant configration in the intact canine heart. In addition, pindolol prolonged the ERP of the ventricle.