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Long QT syndrome

Symptoms of long QT syndrome

Long QT syndrome can cause heart palpitations, where you suddenly feel your heart beating irregularly or faster than usual.

Your heart rhythm usually goes back to normal on its own, but if it continues you may have:

Symptoms can be triggered by exercise, a shock or sudden noise, excitement or stress. They can also happen while you're resting or sleeping.

Many people with long QT syndrome do not have any symptoms. Sometimes it's found when you have a heart rhythm test called an electrocardiogram (ECG) for another reason.

Immediate action required: Call 999 if:

  • someone's not breathing normally and not moving or responding – they could be having a cardiac arrest
  • someone's having a seizure or fit
  • someone's fainted and cannot be woken up within 1 minute

Follow the instructions from the 999 operator until an ambulance arrives.

Urgent advice: Ask for an urgent GP appointment or get help from NHS 111 if:

You've been diagnosed with long QT syndrome, or you're worried you have it, and:

  • you've fainted and have now recovered
  • you have heart palpitations that keep coming back, last longer than a few minutes or are getting worse
  • you've had a seizure or fit and have now recovered

Also ask for an urgent GP appointment if your parent, child, brother or sister has been diagnosed with long QT syndrome, or died unexpectedly. You may need tests to check your heart.

You can call 111 or get help from 111 online.

Tests for long QT syndrome

If a GP thinks you could have long QT syndrome, they'll refer you to a heart specialist (cardiologist) for tests and treatment.

Long QT syndrome is diagnosed using an electrocardiogram (ECG), where sensors are put on your chest to check your heart.

You may also need to:

If you have long QT syndrome, the ECG results will show a pattern in the way your heart beats called a "prolonged QT interval".

As long QT syndrome is usually inherited, you may also be offered genetic testing to see if you have genes linked to the condition.

Important

If you're diagnosed with long QT syndrome, your immediate family should also be offered testing, as there's a chance they could also have the condition.

Treatments for long QT syndrome

Treatment for long QT syndrome depends on the cause, your test results, your symptoms and if you're at high risk of serious problems.

You may be offered:

You'll also be given advice about lifestyle changes to make, and you'll be monitored regularly to check the health of your heart.

Sometimes long QT syndrome is caused by another health condition or medicine. In these cases, treating the condition or stopping the medicine can improve the symptoms.

How to reduce the risk of heart rhythm problems if you have long QT syndrome

If you have long QT syndrome, it's important to avoid triggers that can cause problems with your heart rhythm.

Your care team will give you advice about which lifestyle changes are right for you.

Do

  • check with a doctor or pharmacist before taking any medicines or supplements – some medicines and supplements can cause problems in people with long QT syndrome

  • eat foods containing potassium, such as bananas, some vegetables and pulses – your doctor may also recommend potassium supplements

  • try to avoid sudden noises, such as alarm clocks

  • try to manage stress and anxiety

Don’t

  • do not do strenuous exercise or sports, including swimming

  • do not get dehydrated – you may need rehydration solutions if you're being sick or have diarrhoea

  • do not have energy drinks that contain a lot of caffeine

Causes of long QT syndrome

Long QT syndrome is usually caused by the genes you inherit from your parents.

It can also be caused by:

Help and support for long QT syndrome

If you or someone in your family lives with long QT syndrome, you can get support from charities:

Page last reviewed: 6 January 2025
Next review due: 6 January 2028