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There is controversy whether short QT intervals are associated with sudden death. One trial found QTc intervals < 300ms to be associated with sudden death.<cite>Gaita</cite> However, a recent Finnish study in a random selection of healthy subjects (n=10 822) did not find an increased incidence of sudden death in patients with short QTc intervals. They defined QTc < 320ms as 'very short' and QTc < 340ms as 'short'. In total, 15 deaths occured in the group with QTc <340ms, with only one possible sudden death (cause of death unknown). They used Friderica's method for QTc correction: [[Image:Fridericia.png|100px]].<cite>Fridericia</cite> They conclude that the ECG is not a good screening tool to find patients with a short QTc interval at risk of sudden death.<cite>Anttonen</cite>
<i>Auteur: Louise R.A. Olde Nordkamp</i>
[[File:Sqts.svg|thumb|Precordial ECG tracings of a patient with SQTS]]
<i>Supervisor: Arthur A.M. Wilde</i>
 
The '''short QT syndrome''' is a very rare syndrome characterized by an abnormally short QT interval and increased risk of ventricular fibrillation and cardiac death.
 
==Clinical diagnosis==
[[Image:ShortQT_syndrome_patient.png|thumb|right]]
The diagnosis is based on the presence a short QT interval, in which the upper limit is mostly set on 330 ms. Males are more often affected than women. A history of cardiac arrest is present in one-third. Patients are at risk for both atrial arrhythmias (AF) and ventricular arrhythmias (VT/VF).
 
==Physical examination==
Patients can present with symptoms of arrhythmias:
*Out-of-hospital-cardiac-arrest
*Syncope, pre-syncope (weakness, lightheadedness, dizziness)
 
==ECG tests==
[[Image:Bazett.png|thumb|left]]
The ECG demonstrates a corrected QT interval significantly below the limit of normal (<330 ms). Additionally, notable ECG findings are the presence of a sharp T-wave beginning at the end of the QRS complex, preceded by a brief or absent ST-segment. Exercise electrocardiographic studies in SQTS patients also characteristically reveal a non-physiologic lack of QT shortening at increased heart rates.  
 
==Genetic diagnosis==
[[Image:ShortQT_syndrome_mechanism.png|thumb|left]]
In a quarter of the patients a mutation is found, predominantly in the KCNH2 gene (SQTS1). This gain-of-function mutation causes an increase in the potassium efflux and, subsequently, to a decrease of the myocyte refractory period. Mutations in the KCNQ1, KCNJ2 and possibly CACNxxx genes are also associated with the SQTS.
 
==Risk Stratification==
Risk stratification in SQTS is still ill-defined and should be done by a specialized cardio-genetic cardiologist.
 
==Treatment==
Hydroquinidine is suggested for normalization of the QT interval in patients with a KCNH2 mutation. ICD therapy is advised in SQTS patients for secondary prevention of sudden cardiac death and could be considered
 
 
== References ==
== References ==
<biblio>
<biblio>
#bazett Bazett HC. ''An analysis of the time-relations of electrocardiograms''. Heart 1920;7:353-370.
#Giustetto pmid=16926178
#Lepeschkin pmid=14954534
#Giustetto2 pmid=21798421
#Gaita pmid=12925462
#Patel pmid=20716721
#Anttonen pmid=17679619
#Fridericia Fridericia LS. ''Die Systolendauer im Elektrokardiogramm bei normalen
Menschen und bei Herzkranken''. Acta Med Scand. 1920;53:469–486.
</biblio>
</biblio>
Retrieved from "https://www.textbookofcardiology.org/wiki/Special:MobileDiff/2252"

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