D. Blockage of potassium channels – Explanation
| Long QT syndrome – usually due to loss-of-function/blockage of K+ channels |
In long QT syndrome QT prolongation is due to overload of myocardial cells with positively charged
ions during ventricular repolarisation. Around 90-95% of inherited causes are due to defects in
potassium channels
Long QT syndrome
Long QT syndrome (LQTS) is an inherited condition associated with delayed repolarization of the
ventricles. It is important to recognise as it may lead to ventricular tachycardia and can therefore
cause collapse/sudden death.
The most common variants of LQTS (LQT1 & LQT2) are caused by defects in the alpha subunit of
the slow delayed rectifier potassium channel. A normal corrected QT interval is less than 430 ms in
males and 450 ms in females.
Causes of a prolonged QT interval:
Congenital
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Drugs
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Other
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