title: Quinidine-induced long QTU interval and torsade de pointes: role of bradycardia-dependent early afterdepolarizations.
abstract: Right ventricular endocardial monophasic action potential recordings were obtained in a patient with a qunidine-induced long QTU interval and polymorphic ventricular tachycardia of the torsade de pointes type. The recording showed a deflection on phase 3 repolarization characteristic of early afterdepolarization. The early afterdepolarization was synchronous with the U wave in surface electrocardiographic leads and there was a strong correlation between the amplitude of both waves. A strong correlation was also present between the cardiac cycle length and the U wave amplitude with larger amplitudes after longer cycles. Ventricular ectopic beats occurred only after long cycle lengths and seemed to arise close to the peak of the U wave and early afterdepolarization. However, there was no correlation between the amplitude of the U wave or early afterdepolarization and the occurrence of ectopic beats. Rapid ventricular pacing resulted in suppression of the ectopic rhythm associated with suppression of both the U wave and the early afterdepolarization. This case provides the first evidence to suggest that a quinidine-induced long QTU interval and torsade de pointes may be related to bradycardia-dependent early afterdepolarizations, although other factors may be involved in triggering the arrhythmia.
authors.affiliation: Department of Medicine, State University of New York, Health Science Center, Brooklyn 11203.
authors.forename: N
authors.initials: N
authors.lastname: el-Sherif
authors.forename: S S
authors.initials: SS
authors.lastname: Bekheit
authors.forename: R
authors.initials: R
authors.lastname: Henkin
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000368:Aged; D001919:Bradycardia / Q000150:complications / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D006801:Humans; D008297:Male; D011802:Quinidine / Q000494:pharmacology*; D013610:Tachycardia / Q000150:complications / Q000503:physiopathology* / Q000628:therapy
chemical_list: D011802:Quinidine