Long QT Syndrome: Difference between revisions

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Long QT Syndrome (view source)

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[[Image:acquired_longQT.jpg|thumb|A 12 lead ECG of a patient with acquired long QT syndrome. Notice the QT prolongation. The QTc is about 640ms.]]
The '''Long QT Syndrome (LQTS)''' is characterized on the ECG by prolongation of the [[Conduction#The_QT_interval|heart rate corrected QT interval]]. This was first recognized by Dr. Jervell and Dr. Lange-Nielsen in 1957. They described 4 children with a long QT interval which was accompanied by hearing deficits, sudden cardiac death and an autosomal recessive inheritance.<cite>Lang1957</cite>
The '''Long QT Syndrome (LQTS)''' is characterized on the ECG by prolongation of the [[Conduction#The_QT_interval|heart rate corrected QT interval]]. This was first recognized by dr. Jervell and dr. Lange-Nielsen in 1957. They described 4 children with a long QT interval which was accompanied by hearing deficits, sudden cardiac death and an autosomal recessive inheritance.<cite>Lang1957</cite>
 
The Long QT syndrome may be divided into two distinct forms: congenital Long QT syndrome and acquired Long QT syndrome. These forms may however


The Long QT syndrome may be divided into two distinct forms: congenital Long QT syndrome and acquired Long QT syndrome. These forms may however overlap when QT prolongation due to medication occurs in a patient with congenital Long QT syndrome.
<gallery>
File:acquired_longQT.jpg|A 12-lead ECG of a patient with acquired long QT syndrome. Notice the QT prolongation. The QTc is about 640ms.
File:Lqts1.png|A 12 lead ECG of a patient with genetically proven LQTS1
File:Lqts2.png|A 12 lead ECG of a patient with genetically proven LQTS2
File:Lqts3.png|A 12 lead ECG of a patient with genetically proven LQTS3
</gallery>
===Diagnosis===
===Diagnosis===
*The diagnosis is by maesurement of the [[Conduction#The_QT_interval|heart rate corrected QT interval]] on the ECG, which can be calculated with the [[QTc calculator]].
*The diagnosis is by measurement of the [[Conduction#The_QT_interval|heart rate-corrected QT interval]] on the ECG, which can be calculated with the [[QTc calculator]].
*Sometinmes the QT interval can be difficult to assess. Read the [[Difficult_QT|guidelines for measurement of difficult QT interval]].
*Sometimes the QT interval can be difficult to assess. Read the [[Difficult_QT|guidelines for measurement of difficult QT interval]].
*A QTc of > 500ms in patients with Long QT Syndrome is associated with an increased risk for sudden death.<cite>Priori</cite>  
*A QTc of > 500ms in patients with Long QT Syndrome is associated with an increased risk for sudden death.<cite>Priori</cite>  
*In patients suspected of LQTS (e.g. family members of known LQTS patients) a QTc > 430ms makes it likely that a LQTS gene defect is present.<cite>Hofman</cite>
*In patients suspected of LQTS (e.g. family members of known LQTS patients) a QTc > 430ms makes it likely that a LQTS gene defect is present.<cite>Hofman</cite>
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{| border="1" cellpadding="2" cellspacing="0" bordercolor="#6EB4EB" style="font-size:100%;" class="plainlinks" class="wikitable"
{| border="1" cellpadding="2" cellspacing="0" bordercolor="#6EB4EB" style="font-size:100%;" class="plainlinks" class="wikitable"
|- style="text-align:center;background-color:#6EB4EB;"
|- style="text-align:center;background-color:#6EB4EB;"
| type
| '''Type'''
| chromosome
| '''Chromosome'''
| gene
| '''Gene'''
| protein
| '''Protein'''
| ionchannel
| '''Ionchannel'''
| frequency<cite>priori</cite>
| '''Frequency<cite>priori</cite>'''
| SCD incidence<cite>Shah2005</cite>
| '''SCD incidence<cite>Shah2005</cite>'''
| inheritance
| '''Inheritance'''
| ECG characteristics
| '''ECG characteristics'''
| Trigger
| '''Trigger'''
| Eponyme
| '''Eponyme'''
| [[w:OMIM|OMIM&trade;]] link
| '''[[w:OMIM|OMIM&trade;]] link'''
|-
|-
! LQTS1
! LQTS1
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|-
|-
! LQTS4
! LQTS4
| 4q25
| 4q25-q27
| ANK2
| ANK2
| Ankyrin B
| Ankyrin B
|
| I''Na,K''
| <1%
| <1%
| unknown
|  
| AD
| AD
|
|
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|-
|-
! LQTS5
! LQTS5
| 21q22
| 21q22.1
| KCNE1
| KCNE1
| minK  
| minK  
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|-
|-
! LQTS6
! LQTS6
| 21q22
| 21q22.1
| KCNE2
| KCNE2
| MiRP1
| MiRP1
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| {{OMIM2|603796}}
| {{OMIM2|603796}}
|-
|-
! LQTS7
! LQTS7 = ATS1
| 17q23
| 17q23
| KCNJ2
| KCNJ2
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| {{OMIM2|600681}}
| {{OMIM2|600681}}
|-
|-
! LQTS8
! LQTS8 = TS1
| 6q8A
| 12p13.3
| CACNA1C
| CACNA1C
|  
| Ca<sub>v</sub>1.2
| I''Ca-L''
| I''Ca-L''
| <1%
| <1%
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|
|
| Timothy syndrome
| Timothy syndrome
| {{OMIM2|114205}}
| {{OMIM2|601005}}
|-
|-
! LQTS9
! LQTS9
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| CAV3
| CAV3
| Caveolin 3
| Caveolin 3
|  
| I''Na''
|  
|  
| unknown
| unknown
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| 11q23.3
| 11q23.3
| SCN4B
| SCN4B
| Navb4
| Na<sub>v</sub>1.5 b4
|  
|  
| 1 family
| 1 family
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|  
|  
| {{OMIM2|608256}}
| {{OMIM2|608256}}
|-
! LQTS11
| 7q21-q22
| Akap9
| AKAP
| I''ks''
| 1 family
| unknown
|
|
|
|
| {{OMIM2|611820}}
|}
|}
;LQTS: Long QT syndrome
;LQTS: Long QT syndrome
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;SCD: Sudden Cardiac Death
;SCD: Sudden Cardiac Death
   
   
Long before the genes involved were known, two syndromes had been described that were associated with a prolonged QT interval on the ECG.
Long before the genes involved were known, two syndromes associated with a prolonged QT interval on the ECG had been described.
* Anton Jervell and Fred Lange-Nielsen from Oslo described in 1957 a autosomaal recessive syndrome that was associated with QT interval prolongation, deafness and sudden death: the now called '''Jervell-Lange-Nielsen syndrome'''. <cite>Lang1957</cite>
* Anton Jervell and Fred Lange-Nielsen from Oslo described in 1957 an autosomaal recessive syndrome that was associated with QT interval prolongation, deafness and sudden death: the now called '''Jervell-Lange-Nielsen syndrome'''. <cite>Lang1957</cite>
* '''Romano-Ward syndrome''' is a long QT syndrome with normal auditory function and autosomal dominant inheritance.  
* '''Romano-Ward syndrome''' is a long QT syndrome with normal auditory function and autosomal dominant inheritance.  
* In a genotype–phenotype study by Moss et al. that studied type-1 LQTS, it was found that mutations located in the transmembrane portion of the ion channel protein and the degree of ion channel dysfunction caused by the mutations are important independent risk factors influencing the clinical course of this disorder.<cite>moss</cite>
* In a genotype–phenotype study by Moss et al. that studied type-1 LQTS, it was found that mutations located in the transmembrane portion of the ion channel protein and the degree of ion channel dysfunction caused by the mutations are important independent risk factors influencing the clinical course of this disorder.<cite>moss</cite>
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