Long QT syndrome

Long QT syndrome is an electrical disorder of the heart that affects its rhythm. A person with the condition may experience fast, erratic heartbeats during exercise or at times of emotional excitement. This can lead to fainting, seizures and, in some cases, sudden death. Long QT syndrome is a relatively common cause of sudden death in children and young adults.

The condition is diagnosed using an electrocardiograph (ECG).

Symptoms and when to be investigated#

About one third of people who have long QT syndrome have no symptoms at all. Because of this, the condition is sometimes only discovered after a cardiac event or through screening of a family.

Warning signs that should prompt assessment include:

• fainting for no apparent reason
• fainting during or shortly after exercise or emotional excitement
• a family history of unexplained fainting or sudden death

You should be investigated for long QT syndrome if there is a family history of the condition.

your local emergency number (for example 911 in the US and Canada, 112 across the EU and many countries, 999 in the UK, or 000 in Australia)

Types of long QT syndrome#

There are two main forms: inherited long QT syndrome and acquired long QT syndrome.

Inherited long QT syndrome#

Two inherited forms are recognised:

• Romano-Ward syndrome – increasingly recognised, and the more common inherited form.
• Jervell and Lange-Nielsen syndrome – rare, and also causes deafness.

Researchers have identified more than 15 genes that can cause long QT syndrome, and more are likely to be found in the future. Genetic testing for the condition is now available.

Acquired long QT syndrome#

Long QT syndrome can also be acquired by taking certain over-the-counter and prescription medicines. These can include some:

• diuretics
• antiarrhythmic medications (used to maintain a normal heart rhythm)
• antibiotics
• antidepressants
• antipsychotics
• anti-nausea medications

In some cases, stopping the medicine may prevent further symptoms. In other cases, further treatment may also be required.

If you have long QT syndrome, always tell your doctor before they prescribe a new medicine, as some drugs need to be avoided. Up-to-date lists of medications to avoid are maintained by specialist organisations.

Causes and inheritance#

Long QT syndrome is caused by a change in one of at least 15 different genes. It usually has an autosomal dominant inheritance pattern:

• Dominant means that only one copy of the changed gene is required to cause the condition.
• Autosomal means the gene change occurs on one of the non-sex chromosomes.

If you have long QT syndrome, the chance of passing the changed gene to your child is 50 per cent for each pregnancy, regardless of the sex of the child.

Sometimes the gene change occurs at the time the egg or sperm forms, affecting that child only. This is called a de novo gene change. Genetic testing typically looks for several of the common genes known to be associated with the condition.

If you are found to have long QT syndrome, your biological family members are encouraged to see a cardiologist to have their hearts checked.

Event triggers#

An event can be triggered by strong physical or emotional stimulation, including:

• exercise
• anger or crying
• being startled by a loud noise, such as a horn, a ringing telephone or an alarm clock
• exams, tests or other stressful situations

Treatment#

Treatments include:

• Beta blockers – effective for around 90 per cent of people with long QT syndrome.
• Implantable cardioverter-defibrillators (ICDs) – devices placed inside the body to detect and correct abnormal heart rhythms.

ICDs may be necessary for people who do not respond to beta blocker therapy.

Genetic counselling#

If your child or another family member has been diagnosed with long QT syndrome, or if it runs in your family, it may help to speak to a genetic counsellor. Genetic counsellors are health professionals qualified in both counselling and genetics.

As well as providing emotional support, they can help you understand long QT syndrome and what causes it, how it is inherited, and what a diagnosis means for your or your child’s health and development, and for your family. Genetic counsellors are trained to provide information and support that is sensitive to your family circumstances, culture and beliefs.

If long QT syndrome runs in your family, a genetic counsellor can explain the genetic testing options available to you and other family members. You may choose to see a genetic counsellor if you are planning a family, to find out your risk of passing the condition on to a child, or to arrange prenatal tests.

Support groups can also connect you with other individuals and families affected by long QT syndrome.

Key points#

• About one third of people who have long QT syndrome do not have any symptoms.
• There are two main types of long QT syndrome: inherited and acquired.
• Jervell and Lange-Nielsen syndrome is a rare inherited form that also causes deafness.
• In some cases of acquired long QT syndrome, stopping the medicine may prevent further symptoms.
• In other cases, further treatment may also be required.

Where to get help#