- Short QT syndrome
Name = Short QT syndrome
Caption = Schematic representation of normal ECG trace "(
sinus rhythm)," with waves, segments, and intervals labeled.
DiseasesDB = 11105
Short QT syndrome is a genetic disease of the electrical system of the
heart. It consists of a constellation of signs and symptoms, consisting of a short QT intervalinterval on EKG(≤ 300 ms) that doesn't significantly change with heart rate, tall and peaked T waves, and a structurally normal heart. Short QT syndrome appears to be inherited in an autosomal dominantpattern, and a few affected families have been identified.
ymptoms and signs
Individuals with short QT syndrome frequently complain of palpitations and may have
syncope(loss of consciousness) that is unexplained. Mutations in the "KCNH2", "KCNJ2", and "KCNQ1" genes cause short QT syndrome. These genes provide instructions for making proteins that act as channels across the cell membrane. These channels transport positively charged atoms (ions) of potassium into and out of cells. In cardiac muscle, these ion channels play critical roles in maintaining the heart's normal rhythm. Mutations in the "KCNH2", "KCNJ2", or "KCNQ1" gene increase the activity of the channels, which changes the flow of potassium ions between cells. This disruption in ion transport alters the way the heart beats, leading to the abnormal heart rhythm characteristic of short QT syndrome. Short QT syndrome appears to have an autosomal dominant pattern of inheritance.
Due to the
autosomal dominantinheritance pattern, most individuals will have family members with a history of unexplained or sudden death at a young age (even in infancy), palpitations, or atrial fibrillation.
Short QT syndrome is associated with an increased risk of sudden cardiac death, most likely due to
The diagnosis of short QT syndrome consists of characteristic history and findings on
EKGand electrophysiologic testing. There are currently no set guidelines for the diagnosis of short QT syndrome.
The characteristic findings of short QT syndrome on
EKGare a short QT interval, typically ≤ 300 ms, that doesn't significantly change with the heart rate. Tall, peaked T waves may also be noted. Individuals may also have an underlying atrial rhythm of atrial fibrillation.
In the electrophysiology lab, individuals with short QT syndrome are noted to have short refractory periods, both in the atria as well as in the ventricles. Also,
ventricular fibrillationis frequently induced on programmed stimulation.
The etiology of short QT syndrome is unclear at this time. A current
hypothesisis that short QT syndrome is due to increased activity of outward potassium currents in phase 2 and 3 of the cardiac action potential. This would cause a shortening of the plateau phase of the action potential (phase 2), causing a shortening of the overall action potential, leading to an overall shortening of refractory periods and the QT interval.
In the families afflicted by short QT syndrome,
mutations have been described in three genes, KvLQT1, the "human ether-a-go-go gene( HERG)", and KCNJ2.
Currently, the only effective treatment option for individuals with short QT syndrome is implantation of an
A recent study has suggested that the use of certain
antiarrhythmic agents, particularly quinidine, may be of benefit in individuals with short QT syndrome due to their effects on prolonging the action potential and by their action on the IK channels. [cite journal | author=Gaita F, Giustetto C, Bianchi F, Schimpf R, Haissaguerre M, Calo L, Brugada R, Antzelevitch C, Borggrefe M, Wolpert C. | title=Short QT syndrome: pharmacological treatment | journal=J Am Coll Cardiol | year=2004 | pages=1494–9 | volume=43 | issue=8 | pmid=15093889 | doi=10.1016/j.jacc.2004.02.034] While the use of these agents alone is not indicated at present, there may be benefit of adding these agents to individuals who have already had ICD implantation to reduce the number of arrhythmic events.
Long QT syndrome
*National Library of Medicine. [http://ghr.nlm.nih.gov/condition=shortqtsyndrome?wf=1 Short QT syndrome]
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