The long QT syndromes are a collection of disorders, both acquired and congenital, in which episodes of syncope or presyncope occur secondary to a specific ventrticular tachycardia, «torsade de pointes», which arises in the setting of prolongation of ventricular repolarization as manifested by a prolonged QT interval on the surface electrocardiogram. Untreated, these syndromes have a poor prognosis; in the congenital forms, a mortality of 70% over 15 years is to be expected