Quinidine-induced long QTU interval and torsade de pointes: role of bradycardia-dependent early afterdepolarizations

Department of Medicine, State University of New York, Health Science Center, Brooklyn 11203.

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.

This article has been cited by other articles:

				T. E. Morey, C. N. Seubert, M. J. P. Raatikainen, A. E. Martynyuk, P. Druzgala, P. Milner, M. D. Gonzalez, and D. M. Dennis Structure-Activity Relationships and Electrophysiological Effects of Short-Acting Amiodarone Homologs in Guinea Pig Isolated Heart J. Pharmacol. Exp. Ther., April 1, 2001; 297(1): 260 - 266. [Abstract] [Full Text]

				D. J. Huelsing, K. W. Spitzer, and A. E. Pollard Electrotonic suppression of early afterdepolarizations in isolated rabbit Purkinje myocytes Am J Physiol Heart Circ Physiol, July 1, 2000; 279(1): H250 - H259. [Abstract] [Full Text] [PDF]

				S Viskin, R Fish, D Zeltser, B Belhassen, K Heller, D Brosh, S Laniado, and H V Barron Arrhythmias in the congenital long QT syndrome: how often is torsade de pointes pause dependent? Heart, June 1, 2000; 83(6): 661 - 666. [Abstract] [Full Text]

				P. G.A. Volders, M. A. Vos, B. Szabo, K. R. Sipido, S.H.M. de Groot, A. P.M. Gorgels, H. J.J. Wellens, and R. Lazzara Progress in the understanding of cardiac early afterdepolarizations and torsades de pointes: time to revise current concepts Cardiovasc Res, June 1, 2000; 46(3): 376 - 392. [Full Text] [PDF]

				M. R Franz Current status of monophasic action potential recording: theories, measurements and interpretations Cardiovasc Res, January 1, 1999; 41(1): 25 - 40. [Full Text] [PDF]

				M.-D. Drici, I. Arrighi, C. Chouabe, J. R. Mann, M. Lazdunski, G. Romey, and J. Barhanin Involvement of IsK-Associated K+ Channel in Heart Rate Control of Repolarization in a Murine Engineered Model of Jervell and Lange-Nielsen Syndrome Circ. Res., July 13, 1998; 83(1): 95 - 102. [Abstract] [Full Text] [PDF]

				L. Eckardt, W. Haverkamp, M. Borggrefe, and G. Breithardt Experimental models of torsade de pointes Cardiovasc Res, July 1, 1998; 39(1): 178 - 193. [Abstract] [Full Text] [PDF]

				S. Nattel Experimental evidence for proarrhythmic mechanisms of antiarrhythmic drugs Cardiovasc Res, March 1, 1998; 37(3): 567 - 577. [Abstract] [Full Text] [PDF]

				H. Furushima, S. Niwano, M. Chinushi, K. Ohhira, A. Abe, and Y. Aizawa Relation between bradycardia dependent long QT syndrome and QT prolongation by disopyramide in humans Heart, January 1, 1998; 79(1): 56 - 58. [Abstract] [Full Text] [PDF]