A prolonged QT interval has a variety of causes and can be a very serious ECG finding, as it may lead to the potentially fatal arrhythmia polymorphic ventricular tachycardia (Torsades de Pointes).

The serious complication of QT interval prolongation is polymorphic ventricular tachycardia (Torsades de Pointes) which can be life threatening. Treatment is removing the cause. Polymorphic ...