Long QT syndrome

LQTS explained

LQTS affects the way electricity travels through the heart and can change the way the heart beats.

LQTS is a type of channelopathy. A channelopathy is when your ion channels in your muscles are not working properly. Ions help electrical signals to flow in and out of cells through special channels.

If you have a problem with the ion channels in your heart it can cause abnormal heart rhythms (also known as arrhythmia).

How LQTS affects your heart

Your heart has an electrical system that tells it when to squeeze and relax to pump blood around the body. Ions in your heart help the electrical signals to flow through your heart.

Between each heartbeat, the electrical system recharges. If you have LQTS, your heart takes longer than usual to recharge between beats. When seen on an ECG test (which records the electrical activity of your heart), this delay is called a prolonged (long) QT interval.

Symptoms of LQTS

The symptoms of LQTS can be different for everyone. Many people do not have any symptoms at all, but they can include:

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

If you have LQTS, it’s important to remember that an abnormal heart rhythm can be caused by many things and may return to normal. If it does not, you could be at risk of going into cardiac arrest. Your doctor will talk to you about this and the treatment options.

Causes of LQTS

LQTS can be caused by a gene that is passed down through families. This means it's inherited. 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 medicines you’re taking for other conditions. This is called acquired or drug-induced LQTS. Medicines may include certain types of:

• antibiotics
• antihistamines
• antidepressants
• antipsychotics
• antiarrhythmics
• diuretics.

Risks of 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:

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

Your abnormal heart rhythm may return to normal but if it does not 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 sports, 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.

Diagnosing LQTS

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 on what you know about your family history. They may also ask you about any medicines 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 does not 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 test 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.

Treatments for LQTS

If you have LQTS, you could be given medicines 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 medicine to manage this risk, you may need a pacemaker or an implantable cardioverter defibrillator (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 medicine.

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 medicine or supplements, always check with your pharmacist that what you’re taking is okay with LQTS.

It's important to drink enough after illness. Always tell medical staff you have LQTS.

Living 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 being sick or diarrhoea can affect your sodium and potassium levels. You should discuss this with your doctor who may wish to prescribe oral (to be swallowed) rehydration supplements. These supplements can help to build up 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.

• If you have further questions about inherited heart conditions, call our genetic information service, Monday to Friday, 9am to 5pm. Costs are the same as calling a landline.
• Speak to our cardiac nurses by phone, callback, email or online chat on Heart Helpline, Monday to Friday, 9am to 5pm
• Sign up to our Heart Matters magazine for online information packed with health and lifestyle advice.
• Read about the Rosser family and how they've been affected by Long QT syndrome.