Pathophysiology of long QT syndrome as a cause of sudden cardiac death.

The clinical arrhythmia syndrome where a prolonged QT interval on the surface electrocardiogram is associated with a characteristic form of polymorphic ventricular tachycardia called Torsades de Pointes has been called the long QT syndrome (LQTS). This review of the LQTS covers both acquired and congenital forms. The pathophysiology of the syndrome is discussed in terms of the particular genetic defects, in the case of congenital long QT syndrome, or the particular molecular targets, in the case of the acquired syndrome. The mechanisms of the syndrome are traced from the molecular level, to the cellular level, and finally the clinical presentation. The review concludes with an example for a congenital long QT syndrome where the details of the genetic defect translate into a particular molecular and cellular phenotype that accounts for details of the clinical phenotype. Finally, unanswered questions in the pathophysiology of long QT syndrome are noted.