Congenital long QT syndrome (LQTS) is prolonged ventricular repolarization due to an ion channel mutation, predisposing the individual to polymorphic ventricular tachycardia, manifested as recurrent syncope or sudden cardiac arrest. The prevalence is 1 in 2000 live births, but this may be underestimated. LQTS is a genetic condition affecting the channels that regulate the flow of sodium, potassium, and calcium in cardiac cells. At least 10 genes have been identified thus far, with a spectrum of different clinical features, most commonly KCNQ1 (the cause of LQT1), KCNH2 (the cause of LQT2), and SCN5A (the cause of LQT3).

The different genotypic causes of LQTS also have different clinical presentations. LQT1 patients classically experience arrythmia events during exercise (eg, swimming), while LQT2 patients have events more commonly associated with emotional stress or consequent to loud noises, and LQT3 patients can experience events at rest or even during sleep. LQTS is a leading cause of sudden death in young adults, but it can also present with syncope. The most common arrythmia identified in individuals with LQTS is torsades de pointes.

Related topic: prolonged QT interval