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

J Am Coll Cardiol. 1989 Jul;14(1):252-7. doi: 10.1016/0735-1097(89)90082-x.


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.

Publication types

  • Case Reports
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials / drug effects
  • Aged
  • Bradycardia / complications
  • Bradycardia / physiopathology*
  • Cardiac Pacing, Artificial
  • Electrocardiography*
  • Humans
  • Male
  • Quinidine / pharmacology*
  • Tachycardia / complications
  • Tachycardia / physiopathology*
  • Tachycardia / therapy


  • Quinidine