Short QT syndrome is a newly described cardiologic entity which associates a short OT interval (QT and QTc < or = 300 ms) on the surface ECG to a high risk of syncope or sudden death due to malignant ventricular arrhythmia. This extremely rare syndrome affects mainly young adults or infants and has a wide clinical expression. It is frequently associated with atrial fibrillation. Mutations in 3 different genes KCNQ1, KCNH2, and KCNJ2, all encoding cardiac ionic potassium channels have been identified in affected patients. The clinical spectrum is very wide ranging from asymptomatic carriers to syncope or sudden death. It is an autosomal dominant transmission. Expression studies have shown a gain of function and a shortening of the action potential duration thus explaining the short OT interval. At electrophysiologic study, atrial and ventricular refractory periods are short, and ventricular fibrillation inducible in the majority of patients. As of today, automatic implantable defibrillator is the only effective treatment for the prevention of sudden death in the short QT syndrome.