About UsPatient CareHeart information Center EducationResearchSupport The Texas Heart Institute
Heart Information Center
 
long q-t syndrome
  Back to previous page
  En español

The future of treating heart disease is now.
 
Long Q-T Syndrome
| Share
   
Related terms: LQTS, prolonged Q-T interval, Q-T interval, risk for sudden death, arrhythmia disorder

Long Q-T syndrome (LQTS) is a disorder of the heart's conduction system. The disorder affects a process called repolarization, which is the recharging of the heart after each heartbeat. Congenital LQTS is a rare disorder that is usually inherited (passed down through family members). In other cases, LQTS can be caused by certain medicines, or it can be the result of a stroke or some other neurologic disorder. LQTS can lead to an abnormal heart rhythm (arrhythmia); fainting or loss of consciousness (syncope); or even sudden death.

What causes LQTS?

When your heart contracts, it sends out an electrical signal. The signal is produced by the flow of ions (potassium, sodium, and calcium) within the heart's cells. The ions flow in and out of the heart's cells through ion channels.

Doctors can record the electrical signal produced by the ions on an electrocardiogram (EKG or ECG) machine. The machine makes a tracing of the signal, called a waveform. The different parts of the waveform are represented by the letters P, Q, R, S, and T.

By looking at the waveform, doctors can see the time it takes for the electrical signal to activate and inactivate your heart's lower chambers (the ventricles). This is called the Q-T interval. A problem in one of the ion channels can prolong the Q-T interval. A prolonged Q-T interval can increase your risk for a type of arrhythmia called torsade de pointes. When torsade de pointes occurs, your heart cannot pump enough oxygen-rich blood to the rest of your body, especially your brain. Torsade de pointes can also lead to ventricular fibrillation, a dangerous form of arrhythmia that causes rapid, uncoordinated contractions in the muscle fibers of the ventricles. With ventricular fibrillation, the heart cannot pump oxygen-rich blood to the rest of the body, which can lead to death.

Who is at risk for LQTS?

Long Q-T syndrome can occur in people who seem very healthy. It usually affects children or young adults. You also have an increased risk for LQTS if other members of your family have the disorder.

In some cases, medicines used to treat conditions such as arrhythmia (antiarrhythmics) or depression (antidepressants) may also put you at risk for LQTS.

What are the signs and symptoms of LQTS?

People with LQTS may not have any signs or symptoms. For those who do have symptoms, fainting and arrhythmia are the most common. People with LQTS often show a prolonged Q-T interval during exercise, intense emotion (such as fright, anger, or pain), or as a reaction to a loud or startling noise.

People with LQTS have usually had at least one episode of fainting by the time they are 10 years old. Others may just have 1 or 2 episodes of fainting as children, and then never have another episode again.

In one type of inherited long Q-T syndrome, deafness is part of the disorder.

How is LQTS diagnosed?

The following techniques are commonly used to diagnose LQTS.

  • A standard electrocardiogram (EKG or ECG) is the best test for diagnosing LQTS. The EKG machine records your heart's electrical activity in waveforms, which can show a prolonged Q-T interval.
     
  • An exercise EKG, also known as a stress test, can show an abnormal Q-T interval that may otherwise be normal during a resting EKG.
     
  • Holter monitoring gets a continuous reading of your heart rate and rhythm over a 24-hour period (or longer). You wear a recording device (the Holter monitor), which is connected to small metal disks (called electrodes) on your chest. Doctors can then look at a printout of the recording to see if it shows a prolonged Q-T interval.

Some people with LQTS may not have a prolonged Q-T interval all the time, so the disorder is sometimes overlooked during a routine physical exam. This is why it is important to know your family's medical history. In any family where there are repeated episodes of fainting or a history of sudden death, LQTS may be the cause.

How is LQTS treated?

Treatment for LQTS may include lifestyle changes, medicines, or surgery.

Lifestyle changes

If you are active in competitive sports, talk to your doctor about how this may affect your condition. Often, once treatment in started, patients with LQTS can participate in recreational sports or other activities in moderation. If you have episodes of fainting while you exercise, you may want to think about exercising with a friend or a family member who can call for help if you need it.

Medicines

Medicines called beta-blockers are the most common type of medicine given to patients with LQTS. These medicines do not cure LQTS, but they have been shown to reduce the symptoms of LQTS for those who have them. Beta-blockers are also effective for patients who have been diagnosed with LQTS but do not have any symptoms. In these cases, doctors will most likely prescribe a beta-blocker to prevent the symptoms of LQTS.

Surgery

When LQTS causes uncontrolled ventricular fibrillation, you might need an implantable cardioverter defibrillator (ICD). An ICD is a device that sends an electric shock to your heart to restore a normal heartbeat. The device is placed under the skin of your chest or abdomen and is connected to leads, which are passed through your veins to your heart.

See also on this site:

See on other sites:

American Heart Association
www.heart.org/HEARTORG/Conditions/Arrhythmia/
AboutArrhythmia/Conduction-Disorders_UCM_302046_Article.jsp
  
Conduction Disorders

SADS Foundation 
www.sads.org/About-SADS/Long-QT-Syndrome  
Sudden Arrhythmia Death Syndromes:  LQTS Facts & Online Materials


Updated October 2013
Top  
Texas Heart Institute Heart Information Center
Through this community outreach program, staff members of the Texas Heart Institute (THI) provide educational information related to the prevention, diagnosis, and treatment of cardiovascular disease. It is not the intention of THI to provide specific medical advice, but rather to provide users with information to better understand their health and their diagnosed disorders. Specific medical advice will not be provided and THI urges you to visit a qualified physician for diagnosis and for answers to your questions.
Like us on Facebook Follow us on Twitter Subscribe to us on YouTube Find Us on Flicikr Follow Us on Pinterest Add us on Google+

Please contact our Webmaster with questions or comments.
Terms of Use and Privacy Policy
© Copyright 1996-2014 Texas Heart Institute.
All rights reserved.
This website is accredited by Health On the Net Foundation. Click to verify. U.S. NEWS America's Best Hospitals 2013-14