Difference between revisions of "SQTS"

From Textbook of Cardiology
Jump to navigation Jump to search
(Created page with "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> Howe...")
 
Line 1: Line 1:
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>

Revision as of 01:44, 25 March 2013

Auteur: Louise R.A. Olde Nordkamp Supervisor: Arthur A.M. Wilde

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

ShortQT syndrome patient.png

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

Bazett.png

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

ShortQT syndrome mechanism.png

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

Error fetching PMID 16926178:
Error fetching PMID 21798421:
Error fetching PMID 20716721:
  1. Error fetching PMID 16926178: [Giustetto]
  2. Error fetching PMID 21798421: [Giustetto2]
  3. Error fetching PMID 20716721: [Patel]

All Medline abstracts: PubMed | HubMed