title: Combined effect of verapamil and disopyramide on induction of circus movement tachycardia in patients with pre-excitation.
abstract: By means of intracardiac recordings and programmed electrical stimulation of the heart, the combination effect of verapamil and disopyramide on induction of circus movement tachycardia was studied in 8 patients with anomalous extranodal atrioventricular (A-V) pathway. In 4 of 6 patients who manifested reproducible circus movement tachycardia, verapamil, 0.2 mg/kg intravenously administered, prevented the induction of tachycardia by increasing the A-V nodal refractoriness. Disopyramide in a dose of 2 mg/kg was injected 30 minutes after the start of verapamil administration, when prolongation of the A-V nodal conduction time (A-H interval) had continued in most of the patients. Disopyramide lengthened the effective refractory period of the anomalous pathway in all patients in whom this could be determined. The A-H interval, which had been prolonged by verapamil, was shortened in 4 patients and about unchanged in the remaining 4. After addition of disopyramide, sustained tachycardia could be induced in 2 patients who had lost the ability of initiating circus movement tachycardia after verapamil administration. Thus, disopyramide, when administered together with verapamil, may block the effect of verapamil on the A-V node by its anticholinergic action. A concomitant prescription of disopyramide with verapamil in expectation of the depression of both the anomalous pathway and the A-V node may have an untoward outcome.
mesh_terms: D000293:Adolescent; D000328:Adult; D001283:Atrioventricular Node / Q000503:physiopathology; D004206:Disopyramide / Q000008:administration & dosage / Q000494:pharmacology*; D004357:Drug Synergism; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011725:Pyridines / Q000494:pharmacology*; D012032:Refractory Period, Electrophysiological / Q000187:drug effects; D013610:Tachycardia / Q000139:chemically induced; D014700:Verapamil / Q000008:administration & dosage / Q000494:pharmacology*; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology*
chemical_list: D011725:Pyridines; D014700:Verapamil; D004206:Disopyramide