Congenital short QT syndrome is new inherited clinical syndrome which was described by Gussak et al in 2000. (Cardiology. 2000;94:99-102). A gene mutation causing short QT syndrome was first demonstrated by Brugada et al in January 2004. This mutation in HERG (KCNH2) gene was later called as SQT1 and was due to gain in function of Iks, the slow component of the delayed rectifier potassium current. Later on in the same year, SQT2 was described by Bellocq et al as a mutation in KCNQ1 (KvLQT1) which caused a gain in function of Ikr, the rapid component of delayed rectifier potassium current. SQT3 was identified by Priori et al as a mutation in KCNJ2 gene which causes a gain in function of Ik1 potassium current.
Short QT syndrome is characterized by consistently short QT intervals, usually below 300 msec, which does not lengthen with bradycardia. There is a propensity for sudden cardiac death and atrial fibrillation. Family history of sudden death may be forthcoming. Electrophysiologically short QT syndrome is characterized by short refractory periods and inducible VF (ventricular fibrillation) at EP (electrophysiological) study.
Shortening of QT interval can occur in tachycardia, hyperthermia and hypercalcemia. Digoxin can also shorten the QT interval. These should be excluded before considering a diagnosis of short QT syndrome.
Treatment options for short QT syndrome are limited. Some have reported lengthening of QT interval with quinidine. Most patients with short QT syndrome and a risk of sudden cardiac death get an ICD (implantable cardioverter defibrillator) implanted.