title: Effects of verapamil on accessory pathway properties and induction of circus movement tachycardia in patients with the Wolf-Parkinson-White syndrome.
abstract: The electrophysiological effects of 0.2 mg/kg of intravenously administered verapamil (mean plasma level, 51.3 ng/ml) were evaluated using intracardiac recordings and electrical stimulation in 10 patients with the concealed or manifest Wolff-Parkinson-White syndrome. Verapamil produced a minimal effect on both the antegrade and retrograde effective refractory periods of the accessory pathway and the retrograde conduction time over the accessory pathway, but significantly lengthened the intranodal conduction time as well as the effective and functional refractory periods of the atrioventricular (AV) node. Reproducible sustained circus movement tachycardia was initiated in 8 patients before administration of verapamil and in 2 after verapamil. The sustained tachycardia could no longer be initiated in 6 patients because of an increase in AV nodal refractoriness. In 4 patients, atrial echoes were induced at longer premature beat intervals due to a greater AV conduction delay of the atrial impulse. The cycle length of the tachycardia was lengthened in 2 patients, reflecting an increase in the A-H interval after verapamil administration. In conclusion, these results show that verapamil has no apparent effect on either antegrade or retrograde accessory pathway properties and suggest that verapamil does indeed prevent sustained circus movement tachycardia by increasing the AV nodal refractoriness in some patients with the Wolff-Parkinson-White syndrome.
mesh_terms: D000293:Adolescent; D000328:Adult; D001283:Atrioventricular Node / Q000187:drug effects; D002648:Child; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D014700:Verapamil / Q000097:blood / Q000494:pharmacology*; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology*
chemical_list: D014700:Verapamil