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.