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Long Q-T Syndrome



  • Long Q-T syndrome (LQTS) is a problem with the electric signals that start each heartbeat. It can cause a very fast or irregular heartbeat and can be dangerous and life threatening.
  • Treatment may include medicine to control your child’s heartbeat, or he or she may need an implantable cardiac defibrillator.
  • Your child should stay physically active as advised by your child’s provider. Ask the provider how to take care of your child at home.


What is long Q-T syndrome?

Long Q-T syndrome (LQTS) is a problem with the electric signals that start each heartbeat. It can cause a very fast or irregular heartbeat. Sometimes LQTS can cause a dangerous heart rhythm and be life threatening.

Long Q-T syndrome gets its name from the unusual pattern of the electrocardiogram (ECG or EKG) of people with the disease. An ECG is a test that measures and records your heartbeat.

An electrical signal in the heart starts each heartbeat, causing the heart muscle to squeeze (contract). Normally, this signal starts in the upper right chamber of the heart (the right atrium) at a place called the sinus node. The signal then travels to the upper left atrium and to the lower chambers of the heart (the ventricles).

What is the cause?

Several things can cause LQTS

  • It may be inherited, which means that it is passed from parents to children through their genes. Inside each cell of your body are genes. Genes contain the information that tells your body how to develop and work. Defects in the genes can affect the ability of the heart's muscle cells to use sodium and potassium properly.
  • Some medicines, such as cold medicines, antibiotic medicines, antipsychotic medicines, antidepressant medicines, and diuretic medicine (water pills), can cause LQTS.
  • Eating disorders, severe diarrhea or vomiting, and some thyroid problems may affect the potassium and sodium balance in the heart and cause LQTS.

LQTS is often present at birth but it can appear at any age. It most often occurs in children and young adults.

What are the symptoms?

Most children with LQTS have few or no symptoms. Sudden fainting spells are the most common symptom. Fainting spells are usually brief, but your child may be injured from falling when fainting. Sometimes LQTS may also cause seizures.

Symptoms may happen in response to physical or emotional events such as physical activity, being in cold water, hearing loud noises, laughing, or crying. Sometimes they are triggered by a slow heartbeat, such as when your child is sleeping, and may cause gasping for air.

How is it diagnosed?

Your healthcare provider will ask about your child’s symptoms and medical history and examine your child. Your provider will also ask if any of your family members have had LQTS, unexplained fainting spells, or sudden death. Tests may include:

  • An ECG (also called an EKG or electrocardiogram), which measures and records your heartbeat. Your child may have an ECG while you are resting or while exercising on a treadmill. Your child may also be asked to wear a small portable ECG monitor for a few days or longer.
  • Blood tests

Because LQTS runs in families, if blood tests show that your child has the gene for LQTS, other family members should also be tested.

How is it treated?

Treatment may include:

  • Medicine to help your child’s heart beat more slowly
  • An implantable cardiac defibrillator (ICD), which is a device that can shock your child’s heart back to a regular rhythm. In cases of life-threatening heart rhythm problems, ICDs can provide an instant, life-saving electrical shock before medical help arrives.

Your child may need to avoid activities that may cause symptoms such as certain sports, flying, or scuba diving.

With treatment, children with LQTS can lead normal lives. Most can be physically active and handle emotional stress without fear of symptoms.

How can I take care of my child?

Be sure to take all medicines as prescribed by your healthcare provider.

Help your child learn to manage stress. Teach children and teens to practice deep breathing or other relaxation techniques when feeling stressed. Help your child find ways to relax. For example, take up a hobby, listen to music, play, watch movies, or take walks.

Take care of your child’s health. Make sure your child eats a variety of healthy foods and gets enough sleep and physical activity every day. Talk to your child about the risks of smoking, using e-cigarettes, drinking alcohol, and using drugs.

Follow your healthcare provider's instructions. Ask your child’s healthcare provider:

  • How and when you will get your child’s test results
  • If there are activities your child should avoid and when your child can return to normal activities
  • How to take care of your child at home
  • What symptoms or problems you should watch for and what to do if your child has them

Make sure you know when your child should come back for a checkup. Keep all appointments for provider visits or tests.

Developed by Change Healthcare.
Pediatric Advisor 2022.1 published by Change Healthcare.
Last modified: 2022-01-03
Last reviewed: 2019-11-26
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2022 Change Healthcare LLC and/or one of its subsidiaries
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