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Long QT syndrome information

Long QT syndrome is a rare problem that affects the heart. It results in a fast, abnormal heart rhythm which can lead to other symptoms such as dizziness and fainting.

Usually symptoms appear during childhood or the early teenage years – but in some cases the condition might not be picked up until later in life.

For most people, medication can control the symptoms but some might need a pacemaker or an implantable cardioverter defibrillator (ICD) to regulate the rhythm of the heart.

What causes long QT syndrome and who can get it?

Long QT syndrome affects about one in 10,000 people. It is an inherited condition, in other words it's passed to a child from mum or dad, so you are born with it.

Occasionally a baby might show symptoms of long QT syndrome in the first few weeks after birth, but more often the symptoms don't appear until late childhood or the teenage years.

Long QT syndrome means there is a problem with the heart's conducting or 'electrical' system. The term 'QT' refers to one of the intervals that you can see on an ECG (heart monitor), and it makes up part of the normal heart beat cycle.

But in people with long QT syndrome, this particular interval can be longer than usual, which can disrupt the heart's normal rhythm.

When this happens, the heart begins to beat more quickly and it struggles to supply the body's organs – including the brain – with enough blood and oxygen.

There can be several different triggers for this abnormal rhythm. For instance, intense exercise, emotional excitement or fear can be enough to affect the heart rhythm in this way. Sometimes certain medicines can trigger an abnormal heart rhythm as well.

In general, any abnormal heart rhythm usually lasts for one or two minutes before the heart settles back into a normal rhythm again.

What are the signs and symptoms of long QT syndrome?

Typically a person will suddenly lose consciousness during exercise or when experiencing intense emotions, such as fear.

It can also happen during sleep or when a person is waking from sleep.

Usually there's no warning. For instance, you probably won't feel dizzy beforehand. Most people usually ‘come round' again within one or two minutes as the heart rhythm becomes normal again.

Very occasionally this disruption to heart rhythm can be life-threatening. It's even possible for it to be fatal.

In one in three cases where death results the person appeared quite fit and healthy with no symptoms beforehand. Remember this is very rare.

How is long QT syndrome normally treated?

Treatment usually involves medication in the form of a beta blocker, which works to stabilise the rhythm of the heart. For most people, this is effective.

Others might need further medication, a pacemaker or an ICD to regulate the heart rhythm if the initial medication isn't effective.

When to ask for medical help

If you have experienced fainting that's associated with exercise or strong emotions, and especially if there is a history in your family of the same problem, it's important to discuss it with your GP.

Long QT syndrome is a rare condition but it would be important to rule it out. Your doctor would probably suggest a routine ECG, but this does not always show a long QT interval.

Further tests, including observing you while you are doing some exercise, might help with a diagnosis.

What's going to help?

If you've been diagnosed with long QT syndrome, taking your medication (beta blockers) and avoiding strenuous exercise are the best ways of minimising your risks.

Looking forward

For the vast majority of people diagnosed with long QT syndrome, medication can effectively control their symptoms.

There is genetic testing available for people who have a family history of the condition.

More information

Useful links

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Last reviewed by Great Ormond Street Hospital: 1 June 2010