[Prevention of sudden death in congenital long-QT syndrome].

Congenital long QT syndrome (LQTS) is associated to an increased risk of ventricular arrhythmia, syncope and sudden cardiac death (SD). Four disease genes have been identified and different mutations described in each gene. This locus heterogenicity appears to have important functional and prognostic implications. Sympathetic imbalance has been invoked to explain an arrhythmogenic substrate. Prolonged repolarization is associated to increased dispersion of repolarization enhancing the propensity to develop early afterdepolarizations that may initiate polymorphic ventricular tachycardia (torsade de pointes). Syncope or cardiac arrest usually occur in young patients during exercise, possibly in association with relative bradycardia. The annual incidence of recurrent syncope and SD is 5% and 1%, respectively. Diagnostic criteria include clinical and electrocardiographic variables, family history of early SD and propensity for recurrent syncope. Careful assessment of clinical manifestations and ECG characteristics of family members is justified. Female gender, QTc interval > 500 ms, history of syncope or cardiac arrest are independent risk factors that predict arrhythmic events. Pharmacological agents known to be able to cause QT prolongation or beta-adrenergic stimulation must be avoided. Clinical management of asymptomatic persons with the LQTS is still controversial. Initial treatment of choice for the large majority of patients is administration of propranolol. This treatment is effective in 75-80% of cases. Other therapeutic options include left cervicothoracic sympathectomy, pacemakers, and the implantable cardioverter defibrillator. Risk stratification and efficacy of the subsequent treatment has significantly changed the clinical outcome of patients with LQTS. Recent molecular biology studies and data analysis from the International LQTS Registry may contribute to the definition of the best strategy for the future.