Long QT Syndrome (LQTS)

Long QT syndrome is a problem with the electrical system in your heart taking too long to recharge. This issue can lead to a life-threatening type of abnormal heart rhythm. People can inherit or acquire long QT syndrome. Most people take medication for long QT. Others may need a device or surgery to lower their risk of abnormal heart rhythms.


EKGs of a normal QT interval and a long QT interval from Long QT syndrome.
People with long QT syndrome have a QT interval that’s longer than normal on an EKG.

What is long QT syndrome?

Long QT syndrome refers to an issue with your heart’s electrical system taking longer than normal to recharge between heartbeats.

The QT interval is the section on an electrocardiogram (ECG) report that represents the time it takes your heart muscle to contract and then recover. Put another way, it’s the time it takes for your electrical system to fire an impulse through your ventricles (lower heart chambers) and then recharge.

Ions (electrically charged particles of sodium, calcium, potassium and chloride) produce electrical activity in your heart. Long QT syndrome happens when you have an issue with the ion channels that control the flow of ions in and out of your heart muscle cells.

When these ion channels aren’t working well or you don’t have enough of them, it delays the time it takes your electrical system to recharge after each heartbeat. When the QT interval is longer than normal, it increases the risk for Torsades de Pointes, a life-threatening form of ventricular tachycardia.

Long QT syndrome types

Long QT syndrome has acquired and inherited forms. The types you can inherit (congenital forms) include:

  • Ion channel abnormalities. The most common of these types include LQT1, LQT2, LQT3, LQT4 and LQT5. Researchers classify them by the type of channel that causes the syndrome. Different types have different risk levels for future cardiac events.
  • Jervell and Lange-Nielsen Syndrome. Both parents carry this abnormal gene, but they may not have symptoms of long QT syndrome. This syndrome is extremely rare, as there’s a small chance that both parents would carry the long QT syndrome gene. Each child has a 25% chance of inheriting it. People with this syndrome may be deaf at birth.
  • Romano-Ward Syndrome. One parent has long QT syndrome and the other parent usually doesn’t. Each child has a 50% chance of inheriting the abnormal gene. The abnormal gene may be present in all the couple’s children, some of them or none at all. In this syndrome, hearing abilities are typical.
  • Timothy Syndrome. This is a very rare form of long QT syndrome that affects other parts of your body as well as your heart.

How common is long QT syndrome?

Long QT syndrome is rare. About 1 in 2,000 people in the United States have long QT syndrome.


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Symptoms and Causes

What are the symptoms of long QT syndrome?

The most common long QT syndrome symptoms include:

The symptoms of long QT syndrome appear when the syndrome leads to Torsades de Pointes. During this arrhythmia, your heart can’t pump blood effectively. If your brain doesn’t get enough blood supply, you can faint and have a seizure. If the arrhythmia continues, sudden death will occur. If your heart rhythm returns to normal, symptoms will stop.

Symptoms are most common during:

  • Exercise (or within a few minutes afterward).
  • Emotional excitement, especially when something startles you.
  • Sleep or upon waking suddenly.

Almost 50% of people with long QT syndrome never have symptoms. For 1 out of 10 people with this syndrome, cardiac arrest is the first sign that something is wrong. Without immediate treatment, cardiac arrest is fatal.

People who have symptoms usually start having them during their early teens. If you have symptoms of long QT syndrome, you’ll likely have them again. The risk of symptoms tends to be highest before age 30. However, people can still have them in their 50s and later.

What causes long QT syndrome?

You can inherit long QT syndrome from your parents or acquire it from certain medications. With congenital long QT syndrome, you have an abnormality in the gene code for your ion channels. Abnormal ion channels slow your heartbeat’s recovery phase. This can lead to a life-threatening arrhythmia.

People who get long QT syndrome from certain drugs are those who are inclined to have an issue with their ion channels. People with this issue may not even be aware of it until they take certain medications that trigger long QT.

Medications that can cause acquired long QT syndrome include certain drugs in these categories:

Other causes of acquired long QT syndrome include:

What are the risk factors for long QT syndrome?

People at risk for long QT syndrome include:

  • Children who are deaf at birth.
  • Children and young adults with unexplained sudden death or syncope in their families.
  • Blood relatives of family members with long QT syndrome.
  • People who have cardiomyopathy or congenital (since birth) heart conditions.
  • People with low levels of certain electrolyte components because of a medical issue.
  • People who take medicines that affect their heart’s ion channels.

Do I need a screening for long QT syndrome?

Long QT syndrome is a medical condition that people can pass on from generation to generation. You should get a genetic screening if you have a first-degree relative with long QT syndrome. First-degree relatives are your parents, siblings and children.

All first-line relatives (brothers, sisters, parents and children) should have electrocardiogram (EKG) testing. Any other family members who have a history of seizures or fainting should also undergo testing.

The first step is to tell your healthcare provider that you have a family history of this condition. They may want to do diagnostic tests to check your heart. If these tests are positive, you should see a cardiologist (heart doctor) who is familiar with long QT syndrome.


What are the complications of long QT syndrome?

Long QT syndrome can lead to Torsades de Pointes. This is a life-threatening arrhythmia that can lead to sudden death.

Diagnosis and Tests

How is long QT syndrome diagnosed?

Healthcare providers can diagnose long QT syndrome during a routine electrocardiogram (EKG). To make a diagnosis, they measure the QT interval on the EKG. If your QT interval is longer than 450 milliseconds, you may have long QT syndrome.

Your doctor will ask you if you have a:

  • Family history of long QT syndrome.
  • Family history of unexplained fainting, seizures or cardiac arrest.
  • History of fainting, seizures or cardiac arrest, especially with exercise.

What tests will be done to diagnose long QT syndrome?

In addition to an electrocardiogram (EKG), testing may include:


Management and Treatment

How is long QT syndrome treated?

Long QT syndrome treatments include medications, devices or surgery that help you manage symptoms and prevent sudden death. Treatments don’t provide a cure, but can keep you safer from abnormal heart rhythms.


Most people with long QT syndrome (even those without symptoms) take a beta-blocker such as nadolol. Other medications can shorten your QT interval or improve your electrolyte levels. Your provider will discuss which medications are best for you.


Some people with long QT syndrome also need a device, such as:

  • An implantable cardioverter defibrillator (ICD). People with a history of cardiac arrest or symptoms, even with beta-blocker therapy, may receive an ICD. This device detects life-threatening arrhythmias and automatically shocks your heart to prevent sudden death.
  • A pacemaker. This device helps people who have an abnormally slow heart rate.


Some people with long QT syndrome may need left cardiac sympathetic denervation (LCSD) or a sympathectomy operation. This minimally invasive procedure involves removing specific nerves in your sympathetic nervous system.

Complications/side effects of treatment

Potential side effects or complications depend on the type of treatment you receive:




  • Collapsed lung.
  • Bleeding.
  • Infection.
  • Device malfunction.



Can long QT syndrome be prevented?

You can’t prevent long QT syndrome if you inherited it from your parents. However, people who don’t inherit it can avoid conditions that cause the acquired type of long QT.

Outlook / Prognosis

What can I expect if I have long QT syndrome?

With the right treatment, people with long QT syndrome have a death rate of about 1%. Without treatment, the prognosis is poor. Up to 21% of untreated people with symptoms die within a year after they start fainting.

People with long QT syndrome can live a full life. And they can carry and give birth to children.

How long does long QT syndrome last?

The inherited type of long QT syndrome is a condition people have their whole lives. However, you may have a lower risk of symptoms and complications over time.

Living With

How do I take care of myself?

Long QT syndrome can affect various parts of your everyday life. You’ll need to check with your provider before doing certain things.

Noise and stress

Startling noises or emotional distress can affect people with some types of long QT syndrome. Although you can’t control all the noises and causes of stress around you, you may be able to limit them.

You can try:

  • Letting your friends and family know that it’s not safe to startle you.
  • Using an alarm clock with a pleasant sound instead of a jarring one.
  • Turning down the volume on things that make loud noises and could startle you.


Certain types of long QT syndrome are more likely to cause issues during exercise. Your provider can give you activity guidelines based on the specific type of abnormal gene you carry. Because fatal arrhythmias can happen with exercise, you should talk to your provider when deciding to play competitive sports. You may need to take certain precautions if you decide to take part.

For some people with long QT syndrome, swimming can be dangerous. They can faint while swimming, which can lead to drowning.


Many medications can prolong the QT interval. These drugs may affect people with long QT syndrome more than people who don’t have the syndrome. If you have long QT syndrome, you should:

  • Let all of your healthcare providers know that you have long QT syndrome.
  • Talk to your provider before taking any medications prescribed for other medical conditions.
  • Avoid taking over-the-counter (OTC) medications (except for plain aspirin or acetaminophen) without talking to your provider first.
The following types of medications may affect you if you have long QT syndrome:

When should I see my healthcare provider?

You should see your provider when you start having symptoms and at least once a year after that. An electrophysiologist (provider who specializes in heart rhythms) is the best option.

If your child has long QT syndrome, they should see a provider more than once a year to make sure they’re getting the right dose of medicine for their current weight.

If you have a device, you should see a provider once a year to make sure your device is working correctly.

When should I go to the ER?

A person who’s in cardiac arrest needs immediate medical care. A bystander should start CPR and call 911 or their local emergency number.

What questions should I ask my doctor?

Questions to ask your provider may include:

  • Which type of long QT syndrome do I have?
  • Which specific treatments do you recommend for me?
  • How often do I need appointments with you?
  • Which medicines and activities should I avoid with my particular type of long QT syndrome?

A note from Cleveland Clinic

Knowing you have a heart condition can make you feel anxious. Asking your provider questions and talking to a counselor can help. Be sure to keep your follow-up appointments and take your medications without missing a dose. Letting your family and friends know you have long QT syndrome can give you some peace of mind. They can call for emergency help if you start to have symptoms when they’re with you. Even better, if they know how to do CPR, they could save your life.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 03/20/2023.

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