Torsades de pointes

Abstract

Torsades de pointes are infrequent ventricular polymorphic tachycardias characterized by a typical twisting morphology, some very specific precipitating factors, and a specific treatment. These arrhythmias of variable durations, are often repeated like a rhythmic storm. Despite their rapidity, they may go unrecognized when they are short-lived, but when sustained they may produce syncope and, eventually, can progress to ventricular fibrillation and sudden death. They occur in a setting of acquired or congenital prolonged QT interval. Acquired forms occur most of the time in the elderly, mainly in women, with a history of cardiovascular disease submitted to multiple treatments. QT lengthening results from a combination of several factors (some medications, bradycardia, hypokalemia.). Treatment associates suppression of the risk factors and i.v. infusion of magnesium. In some cases, temporary ventricular pacing is used to accelerate the heart rate. The benefit/risk ratio must be thoroughly weighted before considering prescription of drugs that lengthen repolarisation in these patients. The congenital forms are related to mutations of genes coding potassium channels (Iks, Ikr and their satellites) or, uncommonly, the gene coding the fast sodium channel. Preventing sudden death in children or young adults is obtained by beta-adrenergic antagonistic drugs but ventricular stimulation or implanted defibrillator may be necessary. Drugs that lengthen repolarisation must be prohibited. Genetic family screening is mandatory to detect silent mutation carriers in order to reduce the incidence of sudden death which can be the first expression of the disease.