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Long QT Syndrome: Difference between revisions
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===Diagnosis=== | ===Diagnosis=== | ||
*The diagnosis is by | *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]]. | ||
* | *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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;SCD: Sudden Cardiac Death | ;SCD: Sudden Cardiac Death | ||
Long before the genes involved were known, two syndromes | 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 | * 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> | ||