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Long QT Syndrome

A frowning woman wearing a yellow bathing suit and a yellow swim cap. The woman holds her right hand over her heart, and blue concentric circles radiate from underneath her hand. Four white lines emanate from the heart.
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Last updated January 14, 2021

Long QT syndrome quiz

Take a quiz to find out if you have long QT syndrome.

Long QT syndrome is an electric heart rhythm disorder that can cause fast, chaotic heartbeats. Severe symptoms are sudden fainting and seizures.

Long QT syndrome quiz

Take a quiz to find out if you have long QT syndrome.

Take long QT syndrome quiz

What is long QT syndrome?

Long QT syndrome is an inherited or acquired condition of the heart that results in abnormal heart rhythms (arrhythmias). The heart beats dangerously fast and erratically due to dysfunction in the electrical activity of the heart.

Symptoms include fainting and therefore a higher risk of drowning while swimming, seizures, and sudden death due to cardiac arrest if the heart rhythm is not normalized in time.

Medications and surgery are available to those with inherited long QT syndrome, and the underlying cause is often treated first in those with acquired long QT syndrome. Lifestyle adjustments may also be beneficial in both cases.

You should visit your primary care physician, who will do an ECG to measure the electrical rhythm of your heart, which may identify the diagnosis. Treatment involves stopping meds that could've caused it or a defibrillator.

Long QT syndrome symptoms

Even though long QT syndrome can affect the way your heart beats, the symptoms of long QT syndrome can be subtle and include:

  • Fainting: When the heart beats abnormally, at times enough blood will not be pumped to the brain which can result in fainting. The fainting may occur during a time of heightened emotions such as excitement, anger, fear or stress. They can also occur during times of heightened physical activity such as exercise. Fainting that occurs with long QT syndrome often occurs with little to no warning.
  • Seizures: If the heart continues to beat abnormally, the less oxygen the brain receives, predisposing the brain to seizures.
  • Drowning or near drowning: People with long QT syndrome may faint while swimming, and drowning is often the first manifestation.
  • Sudden death: Usually the heart returns to its normal rhythm; however, if this does not happen by itself in a reasonable amount of time or an external defibrillator is not used to convert the rhythm back to normal, death can occur. This is considered sudden cardiac arrest (SCA).

Long QT syndrome quiz

Take a quiz to find out if you have long QT syndrome.

Take long QT syndrome quiz

Long QT syndrome causes

The electrical activity of the heart is controlled by ion channels that pump sodium, calcium, and potassium in and out of cells. This movement of ions and the electricity created causes the muscle cells of the heart to contract, allowing blood to flow out of the heart to the body. After the heart contracts, there is a relaxation phase in which the heart refills with blood and the cells "recharge" in order to get ready for another contraction.

There are normal durations of time for these contraction and relaxation phases of the heartbeat known as intervals. An electrocardiogram (also known as an EKG or ECG) can show how long these intervals last. The interval of time that the heart takes to recover from contraction and refill with blood before the next contraction is called the QT interval. When the QT interval is too long or prolonged (as in Long QT syndrome), the normal pacing of the heart is disrupted and arrhythmias occur.

Any process that affects the number or function of ion channels on heart cells can result in long QT syndrome. These causes can be either inherited (passed down from generation to generation due to genetics) or acquired. Long QT is considered rare, affecting one in every 5,000 people in the United States. It can also heighten your risk for developing torsade de pointes, another type of arrhythmia.

Inherited Long QT Syndrome

Some people are born with changes in their genes that can result in a prolonged QT interval. There are two described forms of inherited long QT syndrome:

  • Romano-Ward syndrome: This is a more common form that occurs in people who inherit only a single genetic change from one parent.
  • Jervell and Lange-Nielsen syndrome: This is a rare form that usually occurs earlier in life and is more severe. In this type, children inherit genetic changes from both parents. In addition to long QT syndrome, these children are also born deaf.

Acquired Long QT Syndrome

Acquired long QT syndrome can be the result of many different medications, metabolic/electrolyte abnormalities in the body or medical conditions.


Medications that can cause a prolonged QT interval include the following.

  • Antiarrhythmic drugs: Medications used to repair abnormal heart rhythms can result in prolonged QT.
  • Antibiotics: For example, erythromycin or clarithromycin (antibiotics of the macrolide family), as well as levofloxacin.
  • Antihistamines: For example, diphenhydramine or loratadine.
  • Anti-nausea medications
  • Multiple different kinds of antidepressants

Electrolyte abnormalities

Disturbances in the levels of ions such as sodium and potassium in your body due to conditions such as dehydration, severe diarrhea, and even eating disorders can cause long QT syndrome. The QT interval returns to normal when the ions get back to normal.

Who is most likely to be affected

People who can have a higher risk of inherited or acquired long QT syndrome include:

  • All people with unexplained fainting, seizure or near drownings. Especially children, teenagers, and young adults.
  • Family members of children, teenagers, and adults with unexplained fainting, seizure or near drownings since long QT syndrome can be inherited — especially first-degree relatives like brothers, sisters, aunts, and uncles.
  • Individuals taking medications known to cause prolonged QT intervals.
  • People with conditions that can result in low potassium, magnesium or calcium levels in the blood such as eating disorders.

Long QT syndrome quiz

Take a quiz to find out if you have long QT syndrome.

Take long QT syndrome quiz

Treatment options and prevention for long QT syndrome

The goal of treatment for long QT syndrome is to prevent the heart from ever beating out of control or to prevent sudden death or fainting. There are many different options depending on your type of syndrome and your particular risk. Talk to your physician to decide what options are best for you.

Inherited long QT syndrome

Since inherited long QT syndrome is known from birth, it is treated with preventive measures that include:

  • Medications: There are medications such as beta-blockers and specific ion channel medications that can help reduce the risk of symptoms by controlling the heart rate and maintaining electrolyte levels, respectively.
  • Surgery: Surgery can be done to implant a medical device into the heart that can automatically sense and help control arrhythmias. Some examples of such devices include pacemakers and implantable cardioverter defibrillators (ICDs). Another surgery that is done includes surgery to cut part of the nerves to the heart that can cause increased heartbeats during times of emotional stress or exercise. This is known as left cardiac sympathetic denervation surgery.

Acquired long QT syndrome

Treating the underlying cause in acquired long QT syndrome can often eliminate the symptoms. For example, if you are diagnosed with acquired long QT syndrome due to medications, your physician will stop that medication and/or prescribe an alternative. Usually acquired long QT syndrome does not require long-term treatment and management.

At-home treatments

Lifestyle changes you can implement at home include the following.

  • Avoid certain sports: This includes swimming as well as other strenuous exercises, which can cause abnormal heart rhythms. Ask your physician for advice on what types of exercise and sports activities you can participate in.
  • Avoid certain medications: This primarily involves those that may trigger abnormal heart rhythms. This may include some medicines used to treat allergies, infections, high blood pressure, and depression.

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When to seek further consultation for long QT syndrome

Make an appointment with your physician immediately if you experience unexplained episodes of fainting, arrhythmias, or episodes of shortness of breath.

Since long QT syndrome can cause sudden death in otherwise healthy people, it is very important to follow-up on any symptoms you may experience and develop a support system [5,6]. Early detection of a long QT interval can significantly decrease the risk of negative outcomes, so the faster you see your physician, the better.

Questions your doctor may ask to determine long qt syndrome

  • How suddenly do your palpitations appear?
  • Have you been experiencing dizziness?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Place two fingers under your jaw, as shown in the image. How is the rhythm of the heartbeat?
  • How long were you unconscious?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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  1. Long QT syndrome. National Heart, Lung, and Blood Institute. NHLBI Link
  2. Long QT syndrome. Mayo Clinic. Published March 21, 2018. Mayo Clinic Link
  3. Long Q-T syndrome (LQTS). Cleveland Clinic. Cleveland Clinic Link
  4. Long Q-T syndrome. Texas Heart Institute. Texas Heart Institute Link
  5. Long Q-T syndrome (LQTS): Treatment options. Cleveland Clinic. Published May 2017. Cleveland Clinic Link
  6. Living with SADS. Sudden Arrhythmia Death Syndromes. SADS Foundation Link