Short QT syndrome

The short QT syndrome (SQTS) is a recently described genetic arrhythmogenic disorder, characterized by abnormally short QT intervals on surface electrocardiogram (ECG) and a high incidence of sudden death (SD) during life including the first months of life. The inheritance of SQTS is autosomal dominant, with genetic heterogeneity. Gain-of-function mutations in 3 genes encoding potassium channels have been associated to the disease: KCNH2 encoding I-Kr (SQT1). KCNQI encoding I-Ks (SQT2), and KCNJ2 encoding I-K1 (SQT3). Loss-of-function mutations in 3 genes encoding the cardiac L-type calcium channel. CACNAIC, CACNB2b and CACNA2DI may underlie a mixed phenotype of Brugada pattern ECG (or non-specific repolarization changes in case of CACNA2DI) and shorter than normal QT intervals. Clinical presentation is often severe, as cardiac arrest repre sents the first clinical presentation in most subjects. Moreover, often a noticeable family history of cardiac SD is present Atrial fibrilla tion may be observed, also in young individuals. At electrophysiological study, short atrial and ventricular refractory periods are found, and atrial and ventricular fibrillation are easily induced by programmed electrical stimulation. The outcome of patients with SQTS becomes relatively safe when they are identified and treated. Currently', the suggested therapeutic strategy is an implantable cardioverter-defibrillator (ICD) in patients with personal history of aborted SD or syncope. In asymptomatic adult patients from highly symptomatic families and in newborn children pharmacological treatment with hydroquinidine, which has been shown to prolong the QT interval and reduce the inducibility of ventricular arrhythmias, may be proposed.