Key Points about Long QT Syndrome (LQTS)

  • LQTS is a rare condition that affects a small portion of the U.S. population and causes a rapid and chaotic heart rhythm.
  • Primary symptoms for someone with LQTS are fainting, seizures, and sometimes death. However, some people don't have symptoms.
  • Medications can treat LQTS, but surgery may be needed.
Common related conditions
Arrhythmias Atrial Flutter (AFL) Atrial Fibrillation (AFib) Heart Attack


LQTS affects one in 6,000 people in the U.S., making it a rare heart condition. LQTS can cause rapid and chaotic heartbeats that can lead to sudden fainting spells or seizures. In some cases, the heart can beat too fast for an extended period that it can cause sudden death.

The most common symptoms for someone with LQTS are fainting, seizures, sudden death. LQTS is treatable with medications to prevent erratic heart rhythm. Surgery or implanting a device also may be a recommended treatment option for patients with LQTS.

Genetic mutations may put you at risk of being born with LQTS. Medical conditions can cause LQTS and certain medications.

Long QT syndrome causes

During LQTS, it takes longer for your heart muscles to reset and recharge between beats. This is called a prolonged QT interval. Due to abnormalities in the heart's electrical system, the QT interval can become prolonged.

However, many people who have LQTS are born with the condition or have had it their whole life.

Long QT syndrome risk factors

  • Children, teenagers, and young adults have a higher risk of inherited or acquired LQTS. Those with fainting spells, unexplained near-accidents like drowning, unexplained seizures, or have a history of cardiac arrest are likely to have LQTS.
  • People taking medications that are known to cause LQTS.
  • Those with low potassium, magnesium, or calcium blood levels. Typically, people with eating disorder anorexia nervosa have low potassium and are at risk for Long QT syndrome.

Long QT syndrome symptoms

Some people don't experience any symptoms and only know they have the condition from electrocardiogram (ECG) results, family history, or genetic testing.

However, for those who do experience symptoms, they include:

  • Fainting
  • Seizures
  • Sudden death. Typically, the heart will return to normal on its own, but if it doesn’t and using an external defibrillator isn’t working, death will occur.

Long QT syndrome prevention

LQTS is an inherited condition, so there are limited ways to prevent the condition from occurring. Avoiding drugs that are known to prolong the QT interval may prevent some cases.

Also, it is important to seek medical treatment for illnesses that result in low potassium levels. These conditions can cause you to experience a long QT syndrome episode.

Some older adults with long QT syndrome do not experience symptoms and do not need treatment other than preventative measures.

Long QT syndrome diagnosis

Typically, LQTS can be diagnosed and treated by your doctor. If your doctor suspects you have LQTS, they can have a diagnostic test performed, such as:

  • Electrocardiogram (ECG or EKG): Used to monitor and track the electrical impulses to the heart.
  • Holter monitor: Portable ECG used to record heart activity over a short duration of time.
  • Event Monitor: Portable ECG used at the moment the patient feels a symptom so doctors can review your heart rhythm.

Some patients may need other tests to confirm he or she has LQTS. Tests may include:

  • Non-exercise (medication) stress test – an ECG is performed after you are given a medication to simulate activity.
  • Genetic testing – genetic testing can confirm an LQTS diagnosis. If you test positive, your doctor may recommend checking all family members for the condition.

Long QT syndrome treatment

Treatment is used to manage LQTS symptoms and avoid sudden death. Your doctor can develop a plan appropriate for you and will discuss treatment options.

If you are diagnosed with LQTS due to a medication you are taking, your doctor will switch out your medications.

You can also make changes to your lifestyle to help with LQTS to avoid symptoms. Changes include:

  • Family testing
  • Developing an emergency help system with family and friends
  • Modify your exercise routine
  • Avoid medications that cause LQTS

When should I seek care?

If you are taking a new medication for long QT syndrome and feel faint during exercise or when you are emotionally excited, consult your doctor right away.

If you have a first degree relative with long QT syndrome, ask your doctor to test you.

Next Steps

Your doctor will be able to recommend the best treatment for your case. Changes to your medications may be recommended to help prevent some of the risk factors associated with long QT syndrome. Your doctor may advise you not to take drugs that lower blood-potassium levels.

Contact your doctor immediately if your symptoms worsen or change.

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