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Long QT syndrome
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The QT interval is a segment of the electrocardiogram, the recording of the heart's electrical activity. It measures how long the ventricular action potential lasts, that is, the complete electrical cycle of the ventricles. When that segment is prolonged from birth, that is, by congenital causes, it is called long QT syndrome.
It is usually due to mutations in the ion channels, the gates through which electrically charged particles pass in and out: the potassium, calcium, or sodium channels. They work like the locks of a canal, opening and closing to let water through. When those gates fail, too much positive charge is left inside the cell, and the action potential stretches out. The cell takes too long to get back to its starting point.
A prolonged QT can trigger fatal arrhythmias, that is, heart rhythms that can kill. The most common symptom is syncope, or fainting, and it usually happens during exercise or with intense emotion.
In brief
The QT interval on the electrocardiogram measures how long the ventricular action potential lasts; when it is prolonged by congenital causes, it is called long QT syndrome.
It is usually due to mutations in potassium, calcium, or sodium ion channels, which leave excess positive charge in the cell and prolong the action potential.
The cell takes too long to get back to its starting point.
A prolonged QT can lead to fatal arrhythmias; syncope is the most common symptom and usually happens with exercise or intense emotion.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingLong QT Syndrome, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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