Long QT syndrome: symptoms, tests, treatment and living with it

The heart has an electrical system that tells it when to squeeze and relax. The British Heart Foundation (BHF) explains that between each heartbeat the electrical system recharges, and in long QT syndrome the heart takes longer than usual to recharge. On an ECG this delay shows as a prolonged QT interval. LQTS is a type of channelopathy, in which ion channels that allow electrical signals to flow in and out of heart cells do not work properly, which can cause abnormal heart rhythms.

The NHS describes it as a rare heart condition that is usually inherited, and that can cause serious problems with heart rhythm, though there are things you can do to reduce the risk.

The NHS says LQTS can cause heart palpitations, where you suddenly feel your heart beating irregularly or faster than usual. The rhythm usually goes back to normal on its own, but if it continues you may have the following.

• Fainting or blackouts.

• A seizure or fit.

• A cardiac arrest, where the heart beats so fast that not enough blood reaches the brain and the person becomes unconscious and stops breathing.

• Symptoms triggered by exercise, a shock or sudden noise, excitement or stress, or occurring during rest or sleep.

The NHS says to call 999 if someone is not breathing normally and not moving or responding, as they could be having a cardiac arrest, if someone is having a seizure or fit, or if someone has fainted and cannot be woken within 1 minute. The BHF says that if someone is unconscious and not breathing, call 999 and start CPR until medical help takes over, and ask anyone nearby to find a public access defibrillator.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have been diagnosed with long QT syndrome, or are worried you have it, and you have fainted and recovered, have palpitations that keep coming back, last longer than a few minutes or are getting worse, or have had a seizure and recovered. It also says to ask for an urgent GP appointment if your parent, child, brother or sister has been diagnosed with LQTS or died unexpectedly.

The BHF says LQTS can be caused by a gene passed down through families, called congenital LQTS, or by certain medicines, called acquired or drug-induced LQTS. Medicines listed include some types of antibiotics, antihistamines, antidepressants, antipsychotics, antiarrhythmics and diuretics. The NHS says sometimes LQTS is caused by another health condition or medicine, in which case treating the condition or stopping the medicine can improve the symptoms. Never stop a prescribed medicine without advice.

The BHF says abnormal heart rhythms in LQTS can be triggered by a slow heart rate during sleep, a sudden noise, strenuous exercise (particularly swimming) and stress.

The NHS says if a GP thinks you could have long QT syndrome, they will refer you to a cardiologist for tests and treatment. It is diagnosed using an ECG, with sensors put on the chest. You may also need to wear a heart monitor for 24 hours or have an ECG while exercising. As LQTS is usually inherited, you may also be offered genetic testing. The BHF notes that your doctor will ask about family history and any medicines you take, with the ECG as the main way LQTS is checked.

The NHS says treatment depends on the cause, your test results, your symptoms and whether you are at high risk of serious problems.

The NHS says it is important to avoid triggers that can cause problems with heart rhythm, and your care team will give advice on which lifestyle changes are right for you. It advises checking with a doctor or pharmacist before taking any medicines or supplements, because some can cause problems in people with LQTS, eating foods containing potassium, such as bananas, some vegetables and pulses (your doctor may also recommend potassium supplements), trying to avoid sudden noises such as alarm clocks, and managing stress and anxiety. It also lists things to avoid: strenuous exercise or sports, including swimming, getting dehydrated (you may need rehydration solutions if you are being sick or have diarrhoea) and energy drinks that contain a lot of caffeine. The BHF notes that your doctor may advise avoiding competitive sports, which can be difficult for very active people.

Regular monitoring checks the health of the heart. Because the condition is usually inherited, an LQTS diagnosis has implications for relatives, and genetic and inherited cardiac condition services can arrange testing.

In the UK, LQTS is usually managed by cardiologists, often with an inherited cardiac conditions clinic and specialist nurses, who coordinate family testing and device care. Private cardiology can provide faster ECG monitoring or a second opinion, but ICD implantation and family screening are typically coordinated through specialist cardiac services. Always carry a list of your medicines and tell any prescriber that you have LQTS.