Torsades de pointes induced by erythromycin and terfenadine

Abstract

Torsades de pointes is a form of ventricular tachycardia characterized by QRS complexes of changing amplitude that seem to twist around the isoelectric line.’ First described by Dessertenne,’ torsades de pointes has been classified into two categories. Torsades associated with prolongation of the QTc interval and torsades associated with a normal QTc interval.3 Morphologically similar torsades de pointes occurring in patients without QTc prolongation is considered a form of polymorphic ventricular tachycardia and not torsades de pointes.4 Polymorphic ventricular tachycardia associated with QTc prolongation can be caused by electrolyte imbalance, such as hypokalemia, hypomagnesemia, and hypocalcemia, can be related to sinus bradycardia, and can be drug induced. Type Ia antiarrhythmic agents such as quinidine, procainamide, and disopyramide are commonly responsible for lengthening the QTc interval and provoking episodes of torsades that may be manifested by syncope.s-9 Some other medications that have been implicated are: neuroleptic agents,“.” tricyclic antidepressants,” erythromycin,13 trimethoprim-sulfamethoxazole,‘4 astemizole.‘5 and terfenadine. K”