[Proarrhythmic (torsadogenic) effects of QT-prolonging non-antiarrhythmic drugs]

The authors review the rapidly expanding knowledge relating to the arrhythmogenic (torsadogenic) effects of non-antiarrhythmic drugs that lengthen ventricular repolarization (i.e. the duration of electrocardiographic QT interval). After outlining the ECG characteristics and electrophysiological mechanism of drug-induced long-QT syndrome and torsades de pointes ventricular tachycardia, they discuss the concept of repolarization reserve and its role in arrhythmogenesis. Information is provided on the cardiac ion channel background of the proarrhythmic action of QT-prolonging non-antiarrhythmic drugs. The authors present pharmacoepidemiological data on the clinical importance and incidence of this peculiar adverse drug reaction that can in certain cases cause sudden arrhythmic death. They draw attention to the predisposing factors of torsades de pointes ventricular tachycardia, and list those groups of drugs and individual agents that have QT-lengthening and torsadogenic side-effects.