Long QT syndrome

Physical exam

Long QT syndrome (LQTS) is an inherited condition that can cause heart rhythm disturbances.

It occurs in about 1 in 2,000 people.

LQTS may be genetically inherited, but it can also be caused by certain medications you may be taking for other medical conditions.

There are two types of LQTS. In most cases, the condition delays the flow of potassium ions out of heart muscle cells. However, for a small number of people, the sodium channels are affected and too many sodium ions are allowed into the cells.

This causes a delay in the electrical impulse known as ‘prolonged repolarisation’. This shows up on an ECG as a lengthened QT interval, which is part of the heartbeat cycle.

What are the symptoms of LQTS?

The most common symptoms of LQTS are blackouts and palpitations, caused by a disturbance in your heart rhythm. Other members of your family who also have LQTS can experience different symptoms from your own. The symptoms of LQTS depend on:

  • the types of LQTS you have
  • your gender
  • your age, and
  • the length of QT interval (part of the heartbeat cycle).

If you have potassium channel LQTS, you carry the risk of sudden death if you are startled or awoken suddenly. If you have sodium channel LQTS, you have an increased risk of sudden death whilst sleeping.

Your doctor will advise you depending on the type of LQTS you have. You may be advised not to take part in competitive sports, which can be difficult – especially for young people. Your doctor will help you arrive at a balance between being active and reducing your risk of making your condition worse.

The risk of sudden death is greater if you have a history of:

  • previous cardiac arrest
  • blackouts
  • a very long QT interval on your ECG
  • sodium channel mutations.

Strenuous exercise or severe exertion can increase the risk of sudden death for many people with LQTS. Speak to your doctor if you have any questions about the risk of sudden death.

If you are with someone when they collapse suddenly, it is imperative to call 999 and try to perform CPR until an ambulance or medical help arrives. If you are untrained in CPR, the 999 operator will be able to talk you through the process.

How is LQTS diagnosed?

ElectrocardiogramAn ECG is the first test that you will have. You may need repeated ECG recordings or other tests, such as an exercise ECG, which we describe in full in our booklet inherited heart rhythm disturbances.

If you are a carrier of the condition, that is if you have a genetic fault but you don’t have any symptoms, your ECG won’t show any sign of the condition. Genetic testing can sometimes identify carriers of LQTS but it’s limited as 3 in every 10 people diagnosed with LQTS do not have the mutated genes that cause it.

For a definite diagnosis of inherited LQTS, you need to get an expert medical opinion from a clinic that specialises in inherited cardiac conditions.

What treatments are available for LQTS?

Nearly all people with inherited LQTS are treated with medicines. Depending on your symptoms and your risk of having a life-threatening arrhythmia, you may also need to have a pacemaker or ICD fitted or have surgery to control the flow of chemicals into the heart.

If your LQTS has been caused by medicines, these will be reviewed and adjusted so that you still receive the benefits without affecting your QT interval.

If you have a potassium channel LQTS, your doctor may also prescribe potassium supplements or suggest you increase your uptake of potassium-rich foods.

Can I live a normal life with LQTS?

There are very few things you need to change if you have LQTS. However, you should be aware that:

  • Prolonged (longer than a day) or severe episodes of vomiting or diarrhoea can affect your sodium and potassium levels. You should discuss this situation with your doctor who may wish to prescribe oral rehydration supplements. These supplements can help to replenish sodium and potassium levels but should be used under medical supervision.
  • Over-the-counter medicines and supplements should also first be discussed with your doctor. Some of these may induce symptoms or react with medicines you may be taking to help reduce your risk of abnormal heart rhythms.
  • You should always inform medical staff that you have LQTS when you speak to them.

Read about the Rosser family and how they’ve been affected by Long QT

If you have further questions about inherited heart conditions, our Genetic Information Service can help you. Call 0300 456 8383. Lines are open from 9am to 5pm Monday to Friday (charged at a rate similar to 01 or 02 calls).

Want to find out more?

Inherited heart rhythm disturbances booklet

This booklet explains what an inherited heart rhythm disturbance means. It covers screening, testing and implications for the family and future generations. 



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