Long QT syndrome

Long QT syndrome (LQTS) is a rare inherited or acquired 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 irregular heartbeat that originates from the ventricles). These episodes may lead to palpitations, fainting, and sudden death due to ventricular fibrillation. Episodes may be provoked by various stimuli, depending on the subtype of the condition.

The condition is named for the appearance of the electrocardiogram (ECG/EKG) on which a prolongation of the QT interval occurs. Normally, the QT interval duration is between 350 and 440 milliseconds. In some individuals, the QT prolongation occurs after the administration of certain medications, which may be dangerous. In addition to medications, long QT syndrome can be acquired from malnutrition leading to low blood potassium or low blood magnesium, as in anorexia nervosa.

Signs and symptoms

Many people with long QT syndrome have no signs or symptoms.