Effects of N-(2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate on the ventriculo-atrial conductivity of accessory pathways.

The purpose of this study was to examine the effects of N-(2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate (SUN 1165), a newly developed antiarrhythmic agent belonging to class Ic, on the ventriculoatrial (VA) conductivity of accessory pathways and paroxysmal supra-ventricular tachycardia (PSVT). Twelve patients with accessory pathways were examined by standard electrophysiologic technique before and after a single oral dose of SUN 1165 (100 mg). 1 h after administration, SUN 1165 blocked VA conduction of the accessory pathway in six of twelve patients and prevented the induction of PSVT in six of seven cases. In the cases in which VA block did not occur, the VA interval prolonged (from 178 +/- 7 to 190 +/- 11 ms, p less than 0.05), and the effective refractory period of VA conduction was also increased (from 273 +/- 10 to 318 +/- 15 ms. p less than 0.05). SUN 1165 also prolonged the conduction time in normal conduction systems (AH and HV intervals and QRS duration), but the degree of the prolongation was moderate and not dangerous. There was no adverse effect. These results indicate that SUN 1165 is a potent and safe antiarrhythmic agent, and useful for preventing or stopping PSVT by blocking or depressing VA conduction through accessory pathways.