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The LQT3 type of long QT syndrome accounts for 5-10% of cases, and cardiac events can occur during sleep. This variant involves a mutation of the gene that encodes the alpha subunit of the [[sodium|Na<sup>+</sup>]] ion channel. This gene is located on chromosome 3p21-24, and is known as [[SCN5A]] (also hH1 and Na<sub>V</sub>1.5). The mutations involved in LQT3 slow the inactivation of the Na<sup>+</sup> channel, resulting in prolongation of the Na<sup>+</sup> influx during depolarization. Paradoxically, the mutant sodium channels inactivate more quickly, and may open repetitively during the action potential. | The LQT3 type of long QT syndrome accounts for 5-10% of cases, and cardiac events can occur during sleep. This variant involves a mutation of the gene that encodes the alpha subunit of the [[sodium|Na<sup>+</sup>]] ion channel. This gene is located on chromosome 3p21-24, and is known as [[SCN5A]] (also hH1 and Na<sub>V</sub>1.5). The mutations involved in LQT3 slow the inactivation of the Na<sup>+</sup> channel, resulting in prolongation of the Na<sup>+</sup> influx during [[depolarization]]. Paradoxically, the mutant sodium channels inactivate more quickly, and may open repetitively during the [[action potential]]. | ||
A large number of mutations have been characterized as leading to or predisposing LQT3. Calcium has been suggested as a regulator of SCN5A, and the effects of calcium on SCN5A may begin to explain the mechanism by which some these mutations cause LQT3. Furthermore mutations in [[SCN5A]] can cause [[Brugada syndrome]], Cardiac Conduction disease and[[dilated cardiomyopathy]]. Rarely some affected individuals can have combinations of these diseases. | A large number of mutations have been characterized as leading to or predisposing LQT3. Calcium has been suggested as a regulator of SCN5A, and the effects of calcium on SCN5A may begin to explain the mechanism by which some these mutations cause LQT3. Furthermore mutations in [[SCN5A]] can cause [[Brugada syndrome]], Cardiac Conduction disease and [[dilated cardiomyopathy]]. Rarely some affected individuals can have combinations of these diseases. | ||
==References== | ==References== | ||
Revision as of 14:28, 2 October 2012
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Long QT Syndrome Microchapters |
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Diagnosis |
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Treatment |
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Case Studies |
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LQT3 On the Web |
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American Roentgen Ray Society Images of LQT3 |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]
Overview
LQT3 Subtype
| Type | OMIM | Mutation | Notes |
| LQT3 | 603830 | alpha subunit of the sodium channel (SCN5A) | Current through this channel is commonly referred to as INa. Depolarizing current through the channel late in the action potential is thought to prolong APD. The late current is due to failure of the channel to remain inactivated and hence enter a bursting mode in which significant current can enter when it should not. These mutations are more lethal but less common. |
The LQT3 type of long QT syndrome accounts for 5-10% of cases, and cardiac events can occur during sleep. This variant involves a mutation of the gene that encodes the alpha subunit of the Na+ ion channel. This gene is located on chromosome 3p21-24, and is known as SCN5A (also hH1 and NaV1.5). The mutations involved in LQT3 slow the inactivation of the Na+ channel, resulting in prolongation of the Na+ influx during depolarization. Paradoxically, the mutant sodium channels inactivate more quickly, and may open repetitively during the action potential.
A large number of mutations have been characterized as leading to or predisposing LQT3. Calcium has been suggested as a regulator of SCN5A, and the effects of calcium on SCN5A may begin to explain the mechanism by which some these mutations cause LQT3. Furthermore mutations in SCN5A can cause Brugada syndrome, Cardiac Conduction disease and dilated cardiomyopathy. Rarely some affected individuals can have combinations of these diseases.