Long QT syndrome

You have an increased risk for long QT syndrome if other members of your family have the disorder. It's often inherited from a parent as a faulty gene (also called congenital long QT syndrome). 

Medicines

Some medicines can trigger long QT syndrome (called drug-induced long QT syndrome). This usually happens in people with an inherited higher risk of developing it, such as those with slight genetic heart defects. Examples of medicines that may trigger long QT syndrome include:

• antibiotics such as erythromycin, clarithromycin
• antihistamines such as terfenadine (no longer available in Aotearoa New Zealand)
• antidepressants such as citalopram, escitalopram, lithium 
• antipsychotics such as aripiprazole, clozapine, olanzapine and quetiapine
• heart medication such as flecainide, amiodarone, sotalol
• domperidone
• methadone.

Natural products, herbal supplements or dietary supplements 

An example of a natural product that causes long QT syndrome is Artemisia annua. It's also known as Qing hao, Sweet Annie or Sweet Wormwood. It's used as dried herbs or extracts in several natural health products available in Aotearoa New Zealand. New Zealand doesn't have a register of herbal medicines or an approval system for natural products so a complete list of products containing Artemisia annua dried herb or extract can't be provided here. 

If you're at risk of prolonged QT interval, or you're taking QT-prolonging medicines you should avoid products containing Artemisia annua. Carefully check the ingredients of any natural health product or dietary supplement before use. Ask your pharmacist for advice if you are unsure about the product.

See Drugs to avoid(external link) or CredibleMeds(external link) for a list of medicines that should be avoided. Be aware that these websites are not in New Zealand so some of the medicines names may differ.  

Be careful

• Always check with your prescriber or pharmacist if you're not sure if the medicines you've been prescribed are safe.
• Be sure to tell them if you or a family member may have long QT syndrome.  

Many people with long QT syndrome may not have any signs or symptoms. For those who do have symptoms, fainting, blackouts and irregular heart beat are the most common. These episodes can start at any age and may be triggered by:

• stress
• intense emotion (such as fright, anger, or pain)
• a sudden, startling noise such as an alarm bell
• strenuous exercise, particularly swimming
• a slow heart rate during sleep.

However, there isn't always a trigger. Children who are born with long QT syndrome may have at least 1 episode of fainting by the time they are 10 years of age. Others may just have 1 or 2 episodes of fainting as children, and then never have another episode again.

An ECG is the first test that you will have. You may need to repeat ECG recordings or have other tests, such as an exercise ECG.

There are special genetic tests which can be ordered if your healthcare provider suspects you may have a congenital (present from birth) form of QT syndrome. You may also be asked to have one of these tests if you have a close relative with long QT syndrome. 

Long QT syndrome is most commonly treated with medicines called beta-blockers. These work by slowing your heart rate. They do not cure long QT syndrome, but they have been shown to reduce or prevent the symptoms. Read more about beta-blockers.

Depending on your symptoms and your risk of having a life-threatening arrhythmia, you may also need to have an implantable cardioverter-defibrillators (ICD) device fitted. These are devices placed inside your body to detect and correct abnormal heart rhythms. ICDs may be necessary if you don't respond to beta-blocker medicines.

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

If your long QT syndrome is properly treated and controlled, you may not have to make many changes to your normal lifestyle. However, some adjustments may be needed:

• Discuss with your doctor if you need to avoid certain sports or activities that increase the risk of fainting or more serious events.
• Always check the suitability of over-the-counter medicines and supplements with your prescriber or pharmacist. Some may induce symptoms or react with the medicines you're taking to help reduce your risk of abnormal heart rhythms.
• Some people may be advised to avoid sudden startling noises such as alarm clocks or phones – you may need to turn your mobile phone off at night when you go to bed.
• Let your doctor know if you have prolonged (longer than a day) or severe episodes of vomiting (being sick) or diarrhoea (runny poo). This can affect your sodium and potassium levels, which can then affect the signals in your heart. You should discuss this situation with your doctor who may wish to prescribe oral rehydration supplements. These supplements can help to raise your sodium and potassium levels but should be used under medical supervision.  
• Always let whānau and friends know about your condition, or wear a medic-alert bracelet, so that if you faint suddenly they know to call 111 immediately.