G. Torsades de Pointes
This is a pleomorphic form of ventricular tachycardia that usually occurs in the presence of a prolonged QT interval. The RR interval is irregular and the QRS complex shows a characteristic twisting of the points. The ventricular rate varies from 200–300 beats per minute and is usually not sustained for more than a minute. Longer episodes degen¬erate into ventricular fibrillation.
Drugs and conditions that may precipitate torsades de pointes include sotalol, amiodarone, and other antiarrhyth-mic agents; tricyclic antidepressants; antiviral and anti-fungal agents; antibiotics of the erythromycin-azithromycin series; hypokalemia and hypomagnesemia; insecticide poi¬soning; congenital long QT syndrome; cocaine abuse; and chloroquine and pentamidine.

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