Congenital short QT syndrome

Congenital short QT syndrome

Congenital short QT syndrome is an inherited clinical syndrome which was described by Gussak et al in 2000 [1]. A gene mutation causing short QT syndrome was first demonstrated by Brugada et al in January 2004 [2]. 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 [3] 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 [4] 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 ms, 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 [5,6]. Electrophysiologically short QT syndrome is characterized by short refractory periods and inducible ventricular fibrillation at electrophysiology 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 implantable cardioverter defibrillator implanted.

References

  1. Gussak I, Brugada P, Brugada J, Wright RS, Kopecky SL, Chaitman BR, Bjerregaard P. Idiopathic short QT interval: a new clinical syndrome? Cardiology. 2000;94(2):99-102.
  2. Brugada R, Hong K, Dumaine R, Cordeiro J, Gaita F, Borggrefe M, Menendez TM, Brugada J, Pollevick GD, Wolpert C, Burashnikov E, Matsuo K, Wu YS, Guerchicoff A, Bianchi F, Giustetto C, Schimpf R, Brugada P, Antzelevitch C. Sudden death associated with short-QT syndrome linked to mutations in HERG. Circulation. 2004 Jan 6;109(1):30-5.
  3. Bellocq C, van Ginneken AC, Bezzina CR, Alders M, Escande D, Mannens MM, Baró I, Wilde AA. Mutation in the KCNQ1 gene leading to the short QT-interval syndrome. Circulation. 2004 May 25;109(20):2394-7.
  4. Priori SG, Pandit SV, Rivolta I, Berenfeld O, Ronchetti E, Dhamoon A, Napolitano C, Anumonwo J, di Barletta MR, Gudapakkam S, Bosi G, Stramba-Badiale M, Jalife J. A novel form of short QT syndrome (SQT3) is caused by a mutation in the KCNJ2 gene. Circ Res. 2005 Apr 15;96(7):800-7.
  5. Antzelevitch C, Francis J. Congenital short QT syndrome. Indian Pacing Electrophysiol J. 2004 Apr 1;4(2):46-9.
  6. Pérez Riera AR, Ferreira C, Dubner SJ, Schapachnik E, Soares JD, Francis J. Brief review of the recently described short QT syndrome and other cardiac channelopathies. Ann Noninvasive Electrocardiol. 2005 Jul;10(3):371-7.

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