Long QT syndrome

What is LQTS?

LQTS is a channelopathy, a type of disease caused by your ion channels not working properly. Ions are charged atoms which allow electrical signals to flow in and out of cells through special channels and help your body function normally. There are different kinds of ions, including potassium and sodium, which are important for keeping the electrical system of your heart working properly.

The electrical system controls your heart by telling it when to squeeze and relax to pump blood. Between each heartbeat, the electrical system recharges. If you have LQTS, your heart takes longer than usual to recharge between beats.

This is because the channels are not letting the ions in or out of your cells well enough, which causes a delay. When seen on an ECG test (which records the electrical activity of your heart), this delay is called a prolonged QT interval.

What are the symptoms of LQTS?

The symptoms of LQTS vary from person to person. They can depend on the type of LQTS you have, your age and gender. Many people don’t have any symptoms at all, but they can include:

• blackouts
• palpitations
• seizures (caused by a reduced amount of oxygen getting to the brain because of abnormal heart rhythms).

What causes LQTS?

LQTS is usually caused by a faulty gene inherited from your parents. Genes decide how the body works and what parts of you are like, such as eye colour or hair type. If you have the condition from birth, it’s called congenital LQTS.

LQTS is sometimes caused by certain medications you’re taking for other conditions. This is called acquired or drug-induced LQTS. Medications may include certain types of:

• antibiotics
• antihistamines
• antidepressants
• antipsychotics
• anti-arrhythmic medicines
• diuretics.

What are the risks for LQTS?

If you have LQTS, you’re at risk of having an abnormal heart rhythm. This can be triggered by:

• a slow heart rate during sleep
• a sudden noise
• strenuous exercise (particularly swimming)
• stress.

The abnormal heart rhythms you’re at risk of having are:

• Torsades de pointes (a dangerously fast heart rate)
• ventricular fibrillation (when the bottom chambers of your heart quiver instead of beat).

Your abnormal heart rhythm may return to normal but if it doesn’t you’re at risk of sudden cardiac arrest (when your heart stops pumping).

The causes and symptoms of LQTS depend on each person. That’s why your doctor will assess you as an individual. They may advise you to avoid competitive sport, which can be difficult if you’re a very active person or used to exercising at a high level. Ask your doctor anything you might be concerned about.

How is LQTS diagnosed?

There are a few ways in which your doctor will find out if you have LQTS. They include:

• discussion – because LQTS can be inherited, your doctor will ask questions about your family history. They may also ask you about any medications you have been taking
• ECG - to monitor the electrical activity of your heart. This is the main way that LQTS is checked. You may be given a 24-hour ECG monitor to look at your heart for a longer period of time
• exercise ECG – sometimes LQTS doesn’t show up on a standard ECG, so the test needs to be done more than once and in different ways like when you’re exercising.

As LQTS is sometimes inherited, you may also be referred for genetic testing to screen for any faulty genes that are linked with the condition. Your immediate family members (such as your parents, siblings and your children) may also be invited for an assessment.

What treatments are available for LQTS?

If you have LQTS, you could be given medications like beta blockers to treat it. Beta blockers, such as propranolol or nadolol, help control irregular heartbeats and slow your heart rate to make the prolonged QT interval less likely.

If you’re at risk of a life-threatening arrhythmia and you need more than just medication to manage this risk, you may need a pacemaker or ICD fitted. These are fitted to help control the rhythm and rate of your heart or help correct life-threatening heart rhythms.

Some people may need surgery to remove certain nerves that affect the heart to help reduce the chance of a sudden cardiac arrest. This is usually only for people who cannot take medication.

Others with LQTS may need to be prescribed potassium supplements from their doctor. They might also suggest you increase your uptake of potassium-rich foods like bananas, vegetables and pulses. If you’re taking any new medication or supplements, always check with your pharmacist that what you’re taking is okay with LQTS.

It's important to stay hydrated after illness. Always tell medical staff you have LQTS.

Can I live a normal life with LQTS?

With regular check-ups and treatment, you can continue to live a normal and active life. However, you should be aware that:

• if you need an ICD or pacemaker, there may be things to plan for, such as not driving for a little while after having it fitted
• you may have to give up some competitive sports, but your doctor can advise you on physical activity which comes with less risk
• you may have to take potassium supplements prescribed by your doctor or increase the amount of potassium-rich food in your diet
• some over-the-counter medicines or supplements can increase your symptoms so you should discuss these with your doctor and pharmacist before taking them
• prolonged (longer than a day) or severe episodes of vomiting or diarrhoea can affect your sodium and potassium levels. You should discuss this 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.

Get support

Living with LQTS for the rest of your life can be very upsetting for you and your loved ones. You’re not alone. There’s plenty of support to help you lead a good life. Visit our emotional support page for more information on talking about a condition, anxiety, depression, loneliness, bereavement and much more.

Read about the Rosser family and how they've been affected by Long QT syndrome.

Genetic information service

If you have further questions about inherited heart conditions, call our genetic information service, 9am to 5pm, Monday to Friday (costs are the same as calling a landline). Or you can email heart helpline and one of our nurses will get back to you as soon as possible.

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Page last updated: October 2022

Next update due: October 2025