Torsades de pointes and long QT syndromes.

Torsades de pointes is a polymorphic form of ventricular tachycardia that is usually associated with prolongation of the QT interval. This QT prolongation may be either congenital or acquired. Etiologies for the acquired form include hypokalemia, hypomagnesemia, hypocalcemia, starvation, sick sinus syndrome, atrioventricular block and drug effects. Medications that have been implicated include most antiarrhythmic agents, some nonsedating histamine blockers, erythromycin and ketoconazole. Accurate and timely recognition of torsades de pointes is critically important because of the risk that traditional antiarrhythmic drug treatment will likely worsen the problem rather than improve it. Effective treatment requires withdrawal of any offending drugs or correction of the underlying cause of the QT prolongation. Beta blockers have been shown to be effective in preventing problems in congenitally at-risk patients. An implantable cardioverter defibrillator should be considered in some patients with recurrent episodes.