Electrophysiological effects of carocainide (770207) on the dog heart.

The electrophysiological effects of carocainide (770207) were assessed in "in vivo" and "in vitro" experiments on dogs' hearts. Intravenous administration of 5 mg/kg body weight of carocainide significantly lengthened the following: A-H interval, the shortest atrial pacing cycle length maintaining 1:1 atrioventricular (A-V) nodal conduction, H-V interval, left bundle-ventricle (LB-V) interval, the shortest His bundle pacing cycle length maintaining 1:1 His-Purkinje conduction, QRS duration, right atrial and right ventricular effective refractory periods. In Purkinje fiber-papillary muscle junction preparations driven at a constant cycle length of 1000 msec, perfusion of carocainide at the concentration of 1.25 10(-5) M and 2.5 10(-5) M, increased conduction time between Purkinje and muscle fibers and decreased the rate of depolarization of Purkinje fibers and papillary muscle. These results suggest that carocainide depresses conduction and lengthens refractory periods at atrial and ventricular levels and provide an explanation for the positive effect of this compound against experimental cardiac arrhythmias.