The long QT syndrome (LQTS) is a rare inborn heart condition in which delayed repolarization of the heart following a heartbeat increases the risk of episodes of torsades de pointes (TDP, a form of cardiac arrhythmia|irregular heartbeat that ventricular tachycardia|originates from the ventricles). These episodes may lead to palpitations, syncope (medicine)|fainting and sudden cardiac death|sudden death due to ventricular fibrillation. Episodes may be provoked by various stimuli, depending on the subtype of the condition.
The condition is so named because of the appearances of the electrocardiogram (ECG/EKG), on which there is prolongation of the QT interval. In some individuals the QT prolongation occurs only after the administration of certain medications.