[Torsade de pointes induced by quinidine: a case treated successfully with verapamil].

The Authors report a case of incessant torsade de pointes, associated with QT prolongation, due to the proarrhythmic effect of quinidine, which was successfully treated with i.v. verapamil. The arrhythmia occurred after oral administration of quinidine polygalacturonate (550 mg + 275 mg + 275 mg over a 4-hour period) for the conversion of atrial fibrillation in a 41-year-old woman with mild mitral stenosis and regurgitation. Verapamil was administered as an i.v. bolus (5 mg at a rate of 1 mg/min) and with in four minutes the arrhythmia disappeared. The electrophysiological mechanisms of torsade de pointes and the potential role of Ca+(+)-channel-blocking agents in its treatment are briefly discussed.