Long QT syndrome Dr Trisha Macnair The syndrome is a disorder of the electrical system of the heart.

In this article

What is Long QT syndrome? Symptoms

Causes and risk factors Advice and support

An ECG is a recording of the electrical activity of the heart. The QT interval is a measurement on the ECG that correlates to the electrical activity in chambers of the heart called the ventricles (they pump the blood around the body). In long QT syndrome, the duration of repolarisation (or recharging of the electrical system after each heart beat) is longer than normal.

This may result in a very fast, abnormal heart rhythm (an arrhythmia) known as torsade de pointes. When this rhythm occurs, no blood is pumped out from the heart, and the brain quickly becomes deprived of oxygúen, causing sudden loss of consciousness (syncope) and in some cases sudden death.

Symptoms typically begin in pre-teen to teenage years, but may occur in newborns and can appear as late as middle age.

Characteristically, the person suddenly faints or passes out during exercise or when experiencing intense emotions, such as fear, but it can also occur during sleep or arousal from sleep.

There is usually no warning, or sensation of feeling faint or dizzy beforehand. In one in three cases where death results, the person appears quite fit and healthy, with no symptoms at all before cardiac arrest.

Several different genetic problems may cause the condition. But while the genetic abnormality has been identified in some cases, in others the faulty gene has yet to be discovered.

The syndrome, which affects about one in 10000 people, is usually diagnosed by examining a person's electrocardiogram (ECG). Drugs known as beta blockers are effective in controlling the condition in most cases, but some people need treatment with a pacemaker and implantable defibrillator.

In those families where the genetic abnormality has been identified, it may be possible to do prenatal genetic tests for that specific mutation.

CRY (Cardiac Risk in the Young)

Tel: 01737 363222
Email: cry@c-r-y.org.uk
Website: www.c-r-y.org.uk

British Heart Foundation

Tel: 0845 070 8070
Website: www.bhf.org.uk

This article was last medically reviewed by Dr Orlena Kerek in February 2009