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13 Cards in this Set
- Front
- Back
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What mutation is present in LQT1? What is the chanellopathy and what is it associated with?
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1) mutation to KvLQT1 (11p15.5)
2) causing reduced potassium ouflow through slow K+ channels 3) associated with swimming and in homozygous form with deafness ( Jervell-Lange Nielson syndrome) but not in heterozygous form (Romano ward syndrome) |
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What mutation is present in LQT2? What is the chanellopathy and what is it associated with?
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1) HERG (7q35-36)
2) causing reduced potassium ouflow through rapid K+ channels 3) a/w emotion |
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What mutation is present in LQT3? What is the chanellopathy and what is it associated with?
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1) 3p21-24
2) Na channel genes → ↑↑↑ Na influx 3) a/w sleep |
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What mutation is present in LQT4? What is the chanellopathy and what is it associated with?
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1) 4q25 – 26
2) Unknown 3) none known |
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What mutation is present in LQT5? What is the chanellopathy and what is it associated with?
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1) KCNE1 (chr 21)
2) causing reduced potassium ouflow through slow K+ channels 3) associated deafness in homozygous form ( Jervell-Lange Nielson syndrome) but not in heterozygous form (Romano ward syndrome) |
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What mutation is present in LQT6? What is the chanellopathy and what is it associated with?
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1) KCNE2 (chr 21)
2) causing reduced potassium ouflow through rapid K+ channels 3) none |
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How is long QT syndrome treated
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*β-blocker very effective
if additional therapy required: *PPM *implantable defibrillator *sympathectomy |
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What is the prognosis of long QT syndrome?
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*20% mortality in first year of diagnosis
*10 year mortality of undiagnosed *prolonged QT is 50% *with treatment this drops to 5% |
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List common causes of prolonged QT
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*Genetic syndromes:
*Myocardial disease (mitral valve prolapse,myocarditis, cardiomyopathies) *Drugs:(cisipride, erythromycin antihistamines, antiarrhythmics (quinidine, procainamide, amiodarone, sotalol), phenothiazine antipsychotics, TCA, ampicillin, trimethoprim, organophosphates *Electrolyte disturbances (hypocalcaemia,hypomagnasemia) *Metabolic disturbances (hypothermia,hypothyroidism) *Head injuries |
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What proportion of long QT causes have an identifyable cause?
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50 %, the rest are caused by genetic syndromes
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What is the ULN of QTc for an infant 0 - 6 months old? What is it for an older child/ adult
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1) 0.49
2) 0.44 |
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What is the pathophysiology of long QT?
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1)Delayed repolarisation of myocardial cell membranes due to defective sodium or potassium channels.
2) increased influx or reduced efflux of positively charged potassium or sodium into cells 3) delays inactivation of calcium channels allowing further depolarisation instead of repolarisation --> early after depolarisations 4) leading to ventricular arrythmia |
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What is the incidence of long QT?
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1 in 3000
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