[Torsades de pointes]

Abstract

Torsades de pointes are defined and characterised by specific, polymorphic but organised ventricular activation on the surface electrocardiogram. They constitute episodes of rapid tachycardia which are usually short lasting and terminate spontaneously. However, they may recur and persist, leading to syncope or sudden death. They occur typically in cases with abnormalities of ventricular repolarisation with prolongation of the QTU interval and variable deformations of the TU waves. The basal abnormalities may be modest or intermittent. A bigeminy with a long coupling interval and alternating long and short cycles often precede the burst of arrhythmia. Abnormalities of ventricular repolarisation and torsades de pointes may be the result of congenital syndromes (catecholamine-dependent torsades) or acquired factors (pause-dependent torsades) such as paroxysmal bradycardia, drugs which prolong the repolarisation and potassium and magnesium deficiencies. The electrophysiological mechanisms comprise reentry and after depolarisation induced activity genetic factors causing abnormalities of the G-proteins, potassium currents or adrenergic receptors may also play a role. Emergency treatment consists of intravenous magnesium salts, sometimes of betablockers or verapamil for maintenance therapy. The association of a potassium-sparing drug may be useful. Cardiac pacing may be necessary. Left sympathetic denervation or implantation of an automatic defibrillator are exceptional therapeutic options in refractory congenital torsades de pointes.