Novel insights in the congenital long QT syndrome.

BACKGROUND: The congenital long QT syndrome is a potentially fatal, inherited cardiac syndrome. Early diagnosis and preventive treatment are instrumental to prevent sudden cardiac death in patients with the congenital long QT syndrome.
PURPOSE: To review new insights in genetics and cellular electrophysiology, as well as the current understanding of the clinical diagnosis and treatment of the congenital long QT syndrome. DATA SOURCES: Authors' personal databases and search of PubMed database from 1966 to 2001. STUDY SELECTION: Experimental and clinical studies on the congenital long QT syndrome. DATA EXTRACTION: Data from peer-reviewed studies were manually extracted, classified, and summarized. DATA SYNTHESIS: The congenital long QT syndrome is characterized by abnormally prolonged ventricular repolarization, which predisposes patients to syncope, ventricular arrhythmias, and sudden cardiac death. The recent discovery of mutations in genes encoding ion channels has improved our understanding of the cellular origin of this condition. The congenital long QT syndrome may result from inherited defects in cardiac K+ and Na+ channels, which both result in prolongation of the ventricular action potential. The diagnosis is based on electrocardiographic and clinical criteria. Genetic screening of symptomatic patients or asymptomatic family members may identify patients at risk for life-threatening ventricular arrhythmias. beta-Blocking agents are the mainstay of treatment. Certain patients may also benefit from a pacemaker or implantable cardioverter defibrillator. Recent studies suggest that genotype-specific treatment of the congenital long QT syndrome will be feasible in the near future.
CONCLUSIONS: The congenital long QT syndrome is a potentially life-threatening condition caused by mutations in genes encoding cardiac ion channels. Better understanding of the mechanisms responsible for this condition will guide genotype-specific therapy in the near future.