DEVELOPMENTAL ELECTROPHYSIOLOGIC EFFECTS OF PROPAFENONE AND 5-HYDROXYPROPAFENONE ON THE CANINE CARDIAC PURKINJE-FIBER

Standard microelectrode techniques were used to investigate the in vit ro developmental electrophysiologic effects of propafenone and 5-hydro xypropafenone on the adult and neonatal canine Purkinje fiber. The ton ic and frequency-dependent depressant effects of these compounds on V( max) and amplitude were similar in both age groups. However, the abili ty of these compounds to shorten repolarization parameters was more pr onounced in the adult. The extent of reduction of abnormal automaticit y produced by propafenone was greater in the neonate compared to the a dult, and 5-hydroxypropafenone significantly reduced automaticity only in the neonate. The sensitivity of neonatal abnormal automaticity to the effects of these compounds may prove to be important if the use of these agents is to be expanded into the realm of therapy for pediatri c automatic rhythms.