Long QT syndrome

Long QT syndrome (LQTS) is an inherited heart condition. It affects the way the electricity travels through the heart and can change the way the heart beats.

It is usually caused by a faulty gene which is passed from parent to child. A faulty gene can also be referred to as a mutation. Because it is an inherited condition there is usually more than one family member affected.

There are many types of LQTS but most people with the condition have LQTS type 1, LQTS type 2 or LQTS type 3.

Signs and symptoms

Some people have no symptoms but others may notice:

  • blackouts or fainting (these can sometimes look like seizures)
  • palpitations (a feeling that your heart beat has changed or that your heart is suddenly racing for no apparent reason)

Symptoms may be triggered by strenuous exercise, particularly swimming. Other triggers include stress, a sudden or loud noise, for example an alarm clock, and sometimes even sleep.

Tests to confirm the diagnosis

Tests include:

  • an electrocardiogram (ECG) 
  • echocardiogram (ultrasound of the heart) 
  • exercise treadmill test

We may take blood to test for the faulty gene.

Treatment options

The main treatment is a medicine called a beta blocker.

Some patients may need a pacemaker or an implantable cardioverter-defibrillator (ICD). An ICD is a special type of pacemaker that can also deliver an electrical current to the heart to correct an abnormal heart rhythm.

If your symptoms are not controlled by medicine alone you may be considered for a sympathectomy (surgery on the nerves of your spine).

Lifestyle advice

It is very important to follow certain lifestyle advice to reduce the risk of serious heart rhythm abnormalities.

In general you should avoid vigorous sports. Recommendations for exercise vary depending on how prolonged your QT interval is, so please discuss this with your cardiologist.

If you have LQTS type 1 you should avoid strenuous swimming or diving into cold water.

Certain medicines should be avoided. The CredibleMeds website has a list of medicines you should avoid. 

Take action if you experience any of these symptoms

Diarrhoea and sickness (vomiting): if you have diarrhoea and/or sickness use oral rehydration therapy, such as Dioralyte, which can be bought from a pharmacy or shop, to keep well hydrated.

Prolonged diarrhoea and sickness: go to your nearest urgent care centre for blood tests to check your electrolytes, and an ECG to check your QT interval.

Go to your nearest emergency department (A&E) if:

  • you have a blackout

Tell them that you have been diagnosed with LQTS.

Out of hours please contact NHS 111 if you are concerned about any new symptoms. 

MediAlert bracelet: the NHS MedicAlert Foundation has a bracelet you can wear which is helpful to let others know you have LQTS. 

Further information

MedTap is an app created by clinicians at Guy’s and St Thomas’ NHS Foundation Trust.

You can watch short videos which explain more about your condition and your medicines.

You can also set reminders to make sure that you never miss a dose.

Search for MedTap in the App Store or Google Play.

The NHS website has more information about diagnosing, symptoms, and living with LQTS

The British Heart Foundation website also has lots of useful and detailed information about LQTS 

Resource number: 5356/VER1
Last reviewed: May 2023
Next review: May 2026

A list of sources is available on request.

Contact us

If you have any questions or concerns, please contact our team in inherited cardiac conditions.

The inherited cardiac conditions nurses can be contacted Monday to Friday, 9am to 5pm
Email [email protected]
Phone 020 7188 7188 extension 56693

Pharmacy Medicines Helpline

If you have any questions or concerns about your medicine, phone 020 7188 8748, Monday to Friday, 9am to 5pm, or email [email protected]

We try to respond to emails within 2 working days.

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

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