What Is Long QT Syndrome?

Long QT syndrome (LQTS) is a disorder of the heart's electrical activity. It may cause you to develop a sudden, uncontrollable, and dangerous heart rhythm called an arrhythmia (ah-RITH-me-ah) in response to exercise or stress.

Arrhythmias also can develop for no known reason in people who have LQTS. Not everyone who has LQTS develops dangerous heart rhythms. However, if one does occur, it may be fatal.

The term "long QT" refers to an abnormal pattern seen on an EKG (electrocardiogram). An EKG is a test that detects and records the heart's electrical activity. The QT interval, recorded on the EKG, corresponds to the time during which the lower chambers of your heart are triggered to contract and then build the potential to contract again. These chambers are called ventricles (VEN-trih-kuls).

The timing of the heartbeat's electrical activity is complex, and the body carefully controls it. Normally the QT interval of the heartbeat lasts about a third of each heartbeat cycle on the EKG.

However, in people who have LQTS, the QT interval usually lasts longer than normal. This can upset the careful timing of the heartbeat and trigger a dangerous, abnormal rhythm.

Overview

On the surface of each muscle cell in the heart are tiny pores called ion channels. Ion channels open and close to let electrically charged sodium, calcium, and potassium atoms (ions) flow into and out of the cell. This generates the heart's electrical activity.

This activity causes each heart cell to contract. Normally, the electrical activity spreads from one heart cell to the next in an orderly and coordinated way. This allows the heart to pump blood.

During each normal heartbeat, the muscle cells in the upper chambers of the heart, the atria (AY-tree-uh), contract. The contraction pumps blood from the atria to the ventricles. Then the muscle cells in the ventricles contract, pumping blood from the ventricles to the lungs and the rest of the body.

This coordinated contraction of the atria and ventricles represents one normal heartbeat.

In people who have LQTS, problems with the ion channels in the heart cells may disrupt the timing of the electrical activity in the ventricles. The ion channels may not work properly, or there may be too few of them. In this situation, the heart may suddenly develop a fast and abnormal heart rhythm that can be life threatening.

Many cases of LQTS are inherited, which means you're born with the condition and have it your whole life. There are seven known types of inherited LQTS. The most common ones are called LQTS 1, LQTS 2, and LQTS 3.

Emotional stress or exercise (especially swimming) that makes the heart beat fast tends to trigger abnormal heart rhythms if you have LQTS 1. In LQTS 2, abnormal rhythms may be triggered by surprise or other extreme emotions. In LQTS 3, a slow heart rate during sleep may trigger an abnormal heart rhythm.

Acquired, or noninherited, LQTS may be brought on by certain medicines or other medical conditions.

Outlook

More than half of the people who have an untreated, inherited form of LQTS die within 10 years. But for many people who have LQTS, lifestyle changes and medical treatments can help prevent dangerous complications and lengthen life expectancy.

Some of these lifestyle changes and treatments include:

• Avoiding strenuous physical activity or startling noises
• Adding more potassium to your diet
• Taking heart medicines called beta blockers, which are very effective at preventing sudden cardiac arrest
• Having an implanted medical device, such as a pacemaker or implantable cardioverter defibrillator, that helps control abnormal heart rhythms

Discuss with your doctor which lifestyle changes and treatments are appropriate for you and the type of LQTS you have.

Other Names for Long QT Syndrome

• Jervell and Lange-Nielsen syndrome
• Romano-Ward syndrome

What Causes Long QT Syndrome?

Inherited Long QT Syndrome

Faulty genes cause inherited long QT syndrome (LQTS). These genes control the production of certain types of ion channels in your heart. The genes may cause the body to make too few ion channels or ion channels that don't work properly, or both.

If you have inherited LQTS, you received the faulty gene(s) from one or both of your parents. Inherited LQTS is a lifelong condition.

There are seven known types of inherited LQTS (types 1 though 7). The most common types of inherited LQTS are types 1, 2, and 3. Some types of LQTS stem from either faulty or lacking potassium ion or sodium ion channels.

If you have LQTS 1 or LQTS 2, the flow of potassium ions through the ion channels in your heart cells isn't normal. This may cause problems when you exercise or when you're surprised or experience emotional stress.

During these situations, you may develop a rapid and uncontrollable heart rhythm that prevents your heart from pumping blood. This will result in death if it's not quickly brought under control.

If you have LQTS 3, the flow of sodium ions through ion channels in your heart cells isn't normal. This can trigger a rapid and uncontrollable heart rhythm that can be fatal. In LQTS 3, problems usually occur when your heart beats slower than normal, such as during sleep.

Acquired Long QT Syndrome

Certain medicines or other medical conditions can cause acquired, or noninherited, LQTS.

Medication-Induced Long QT Syndrome

Presently, more than 50 medicines have been recognized to cause LQTS. Some of the commonly used medicines that may cause LQTS include:

• Antihistamines and decongestants
• Diuretics (pills that remove excess water from your body)
• Antibiotics
• Antidepressants
• Cholesterol-lowering medicines and some diabetes medicines

Some people who have medication-induced LQTS also may have an inherited form of the syndrome that doesn't cause symptoms unless they take certain medicines that lengthen the QT interval or lower potassium levels in the blood. When LQTS doesn't cause symptoms, it's called silent LQTS.

Other Causes of Acquired Long QT Syndrome

Excessive diarrhea or vomiting that causes a major loss of potassium or sodium ions from the bloodstream may cause LQTS. The syndrome lasts until the levels of these ions in the blood return to normal.

The eating disorder anorexia nervosa and certain thyroid disorders may cause a drop in potassium ion levels in the blood, causing LQTS.

Who Is At Risk for Long QT Syndrome?

Long QT syndrome (LQTS) is a rare condition. Experts think that about 1 in 7,000 people has LQTS. But no one knows for sure, because LQTS often goes undiagnosed.

LQTS causes about 3,000 to 4,000 sudden deaths in children and young adults each year in the United States. Unexplained sudden death in children is rare. But when it does occur, LQTS often is the cause.

Inherited LQTS usually is first detected during childhood or young adulthood. Half of all people who have LQTS have their first abnormal heartbeat by the time they're 12 years old, and 90 percent by the time they're 40 years old. The condition rarely is diagnosed in someone after age 40.

In boys who have LQTS, the QT interval (on the EKG) often returns toward normal after puberty. If this happens, the risk for LQTS symptoms and complications decreases.

LQTS is more common in women than men. Women who have LQTS are more likely to faint or die suddenly from the condition during menstruation and shortly after giving birth.

LQTS also is common in children who are born deaf. This is because the same genetic problem that affects hearing also affects the function of ion channels in the heart.

Major Risk Factors

You're at risk for having LQTS if anyone in your family has ever had it. Unexplained fainting or seizures, drowning or near drowning, or unexplained sudden death are all possible signs of LQTS.

You're also at risk for LQTS if you take medicines that make the QT interval longer. Your doctor can tell you whether prescription or over-the-counter medicines you take might do this.

You also may develop LQTS if you have excessive vomiting or diarrhea or other conditions that cause low blood levels of potassium or sodium. These conditions include the eating disorders anorexia nervosa and bulimia and certain thyroid disorders.

What Are the Signs and Symptoms of Long QT Syndrome?

Major Signs and Symptoms

If you have long QT syndrome (LQTS), you're prone to developing a sudden and dangerous arrhythmia (abnormal heartbeat). Signs and symptoms of LQTS-related arrhythmias often first appear during childhood and include:

• Unexplained fainting. This happens because your heart isn't pumping enough blood to your brain. Fainting may occur when you're under physical or emotional stress. Some people will have fluttering feelings in their chests before they faint.
• Unexplained seizures. Those around you may mistake your fainting from LQTS as a seizure due to epilepsy. In children, fainting may be seen as a hysterical reaction to a stressful situation.
• Unexplained drowning or near drowning. This may be due to fainting while swimming.
• Unexplained sudden cardiac arrest (SCA) or death. This means that your heart suddenly stops beating for no obvious reason. People who have SCA will die within minutes unless they receive treatment. Most people who have SCA die. In about 1 out of 10 patients, SCA or sudden death is the first sign of LQTS.

Other Signs and Symptoms

Often, people who have LQTS 3 will develop an abnormal heartbeat during sleep. This may cause them to have noisy gasping while sleeping.

Long QT Syndrome Without Symptoms

People who have LQTS may not have any signs or symptoms (silent LQTS). Doctors often advise family members of people who have the condition to be tested for it, even if they have no symptoms.

Medical and genetic tests may reveal whether they have LQTS and what type of the condition they have.

How Is Long QT Syndrome Diagnosed?

Cardiologists diagnose and treat long QT syndrome (LQTS). Cardiologists are doctors who specialize in treating heart diseases and conditions. To diagnose LQTS, doctors consider:

• EKG (electrocardiogram) results
• Medical history and physical exam
• Genetic test results

EKG

An EKG is a simple test that detects and records the heart's electrical activity. This test may reveal a long QT interval and other signs that make it more likely that you have LQTS. Often, doctors first discover a long QT interval when an EKG is done for another suspected heart problem.

Not all people who have LQTS will always have a long QT interval on an EKG. The QT interval may change from time to time; it may be long sometimes and normal at other times. Because of this, your doctor may want you to have several EKG tests over a period of days or weeks. Or, your doctor may have you wear a device called a Holter monitor.

A Holter monitor records the electrical signals of your heart for a full 24- or 48-hour period. You wear small patches called electrodes on your chest that are connected by wires to a small, portable recorder. The recorder can be clipped to a belt, kept in a pocket, or hung around your neck.

While you wear the monitor, you do your usual daily activities. You also keep a notebook, noting any symptoms you have and the time they occurred. You then return both the recorder and the notebook to your doctor to read the results. Your doctor can see how your heart was beating at the time you had symptoms.

The purpose of a Holter monitor is to detect heart problems that may occur for only a few minutes out of the day.

Some people will only have a long QT interval on an EKG recording while they exercise. For this reason, your doctor may recommend that you have a stress test.

For this test, an EKG is done while you exercise. If you're unable to exercise, medicine may be injected into your bloodstream to make your heart work hard and beat fast, as if you were exercising.

Medical History and Physical Exam

Your doctor will ask whether you've had any symptoms of an abnormal heartbeat. Symptoms may include:

• Unexplained fainting
• A fluttering feeling in your chest, which is the result of your heart beating too fast
• Loud gasping during sleep

Your doctor may ask what over-the-counter, prescription, or recreational drugs you take. He or she also may want to know whether anyone in your family has been diagnosed with or shows signs of LQTS. Signs of LQTS include unexplained fainting or seizures, drowning, sudden cardiac arrest, or sudden death.

Your doctor will examine you and look for signs of conditions that may lower blood levels of potassium or sodium. These conditions include the eating disorders anorexia nervosa and bulimia, excess vomiting or diarrhea, and certain thyroid disorders.

Genetic Tests

Genetic blood tests can detect some forms of inherited LQTS. If your doctor suspects that you have LQTS, he or she may recommend genetic testing. Genetic blood tests usually are suggested for family members of people who have LQTS as well.

However, genetic tests can't detect about one-third of LQTS cases. So, even if you have LQTS, the tests may not show it.

Also, as many as one-third of the people who test positive for LQTS don't have any signs or symptoms of the disorder. These people may have silent LQTS. Less than 10 percent of these people will faint or suddenly die from an abnormal heartbeat.

Even if you have silent LQTS, you may be at higher risk than most people for developing an abnormal heartbeat while taking medicines that affect potassium ion channels or blood levels of potassium.

Types of Inherited LQTS

If you have inherited LQTS, it may be helpful to know which of the seven inherited types of the syndrome you have. This will help you and your doctor plan your treatment and decide which lifestyle changes you should make.

To find out what type of LQTS you have, your doctor will consider:

• Genetic test results
• The types of situations that trigger an abnormal heartbeat
• How well you respond to medicine

How Is Long QT Syndrome Treated?

The goal of treating long QT syndrome (LQTS) is to prevent life-threatening, abnormal heartbeats and fainting spells. Treatment isn't a cure for this condition and may not restore a normal QT interval on an EKG. But treatment does greatly improve survival.

Specific Types of Treatment

Your doctor will recommend the best treatment for you based on:

• Whether you've had symptoms, such as fainting or sudden cardiac arrest (SCA)
• What type of LQTS you have
• How likely it is that you'll faint or that your heart will suddenly stop beating
• What treatment you feel most comfortable taking

People who have LQTS but no symptoms may be advised to:

• Make lifestyle changes that reduce the risk of fainting or SCA. These may include avoiding competitive sports and strenuous exercise, such as swimming, which can cause abnormal heartbeats.
• Avoid medicines that may trigger symptoms. This may include some medicines used to treat allergies, infections, high blood pressure, high blood cholesterol, and depression.
• Take medicines, such as beta-blockers, which reduce the risk of symptoms by slowing your heart rate.

The type of LQTS you have will determine which medicines you take to avoid abnormal heart rhythms. For example, doctors usually only will prescribe sodium channel blocker medicines for people who have LQTS 3.

If your doctor thinks you're at higher risk for LQTS complications, he or she may suggest other more aggressive treatments (in addition to medicines and lifestyle changes). Such aggressive treatments include:

• A surgically implanted device, such as a pacemaker or implantable cardioverter defibrillator (ICD). These devices help regulate your heartbeat.
• Surgery on the nerves that regulate your heartbeat.

People at higher risk are those who have fainted or who have developed dangerous heart rhythms from their LQTS in the past.

Lifestyle Changes

If you have LQTS, you should try to avoid, if possible, the specific triggers you have for an abnormal heartbeat. Many people who have LQTS also benefit from adding more potassium to their diets.

Check with your doctor about eating more potassium-rich foods, such as bananas, or taking potassium supplements daily.

People who have LQTS also should avoid medicines that lengthen the QT interval or lower potassium blood levels.

Medicines

Beta blockers are medicines that prevent the heart from beating faster in response to physical or emotional stress. Most people who have LQTS are treated with beta blockers.

Doctors may suggest that people who have LQTS 3 take sodium channel blockers, such as mexiletine. These medicines make sodium ion channels less active.

Pacemaker or Implantable Cardioverter Defibrillator

These surgically implanted devices monitor the heart rhythm. They deliver electrical currents to the heart when they detect an abnormal heart rhythm. Surgeons implant pacemakers and ICDs in the chest or belly with a minor procedure.

Surgery

People who are at high risk of death from LQTS are sometimes treated with surgery. During this surgery, the nerves that prompt the heart to beat faster in response to physical or emotional stress are cut.

This helps keep the heart beating at a steady pace and decreases the chances of developing dangerous heart rhythms in response to stress or exercise.

Living With Long QT Syndrome

Long QT syndrome (LQTS) usually is a lifelong condition. The risk of developing an abnormal heartbeat that leads to fainting or sudden cardiac arrest may lessen as you age, but the risk never disappears.

You'll need to take certain steps for the rest of your life to prevent abnormal heartbeats and to ensure that you get treatment right away if one occurs. These steps include:

• Avoiding things that trigger an abnormal heart rhythm
• Letting others know you might faint or your heart might stop beating, and what steps they can take
• Having a plan in place for when you develop an abnormal heartbeat

Avoid Triggers

If exercise triggers an abnormal heartbeat, your doctor may recommend that you avoid any strenuous exercise, especially swimming. Ask your doctor about which types of exercise are safe for you.

If you have a pacemaker or implantable cardioverter defibrillator, avoid contact sports that may dislodge these devices. You may want to only exercise in public or with a friend who can help you if you faint.

Avoid medicines that may trigger an abnormal heartbeat. This includes some medicines used to treat allergies, infections, high blood pressure, high blood cholesterol, and depression. Consult with your doctor before taking any prescription, over-the-counter, or other medicines or drugs.

Seek medical care right away for conditions that lower the sodium or potassium level in your blood. These conditions include the eating disorders anorexia nervosa and bulimia, excess vomiting or diarrhea, and certain thyroid disorders.

If you have LQTS 2, try to avoid unexpected noises, such as loud or jarring alarm clock buzzers and telephone ringers.

Inform Others

You may want to consider wearing a medical ID necklace or bracelet that states that you have LQTS.

Let your roommates, coworkers, or other people with whom you have regular contact know that you have a condition that might cause you to faint or your heart to stop beating. Tell them to call 9–1–1 right away if you faint.

You may want to ask someone in your family or office to learn cardiopulmonary resuscitation (CPR) in case your heart stops beating.

You also may want to keep an automatic external defibrillator with you at home or at work. This device uses electrical shocks to restore your heartbeat to normal. Someone at your home or workplace should be trained on how to use the device if your heart stops beating.

If you have LQTS 3 and you sleep alone, you may want to have an intercom in your bedroom connected to someone else's bedroom. This will let others detect the noisy gasping that often occurs if you develop an abnormal heartbeat while lying down.

Ongoing Health Care Needs

You should see your cardiologist (heart specialist) regularly. He or she will adjust your treatment as needed. For example, if you still faint often while using less aggressive treatments, your doctor may recommend other options to better prevent the abnormal heart rhythms you're having.

Emotional Issues and Support

Living with LQTS may cause fear, anxiety, depression, and stress. It's important to talk about how you feel with your health care team. Talking to a professional counselor also can help. If you're feeling very depressed, your health care team or counselor may prescribe medicines to make you feel better.

Joining a patient support group may help you adjust to living with LQTS. You can see how other people have coped with the condition. Talk to your doctor about local support groups or check with an area medical center.

Support from family and friends also can help relieve stress and anxiety. Let your loved ones know how you feel and what they can do to help you.

Some people learn they have LQTS when they're tested after a family member has died suddenly from LQTS. Grief counseling may help you cope if this has happened to you. Talk to your doctor about how to find a grief counselor.

Key Points

• Long QT syndrome (LQTS) is a disorder of the heart's electrical activity. It may cause you to develop a sudden, uncontrollable, and dangerous heart rhythm called an arrhythmia in response to exercise or stress.
• Arrhythmias also can develop for no known reason in people who have LQTS. Not everyone who has the disorder develops dangerous heart rhythms, but if one does occur, it may be fatal.
• LQTS is a rare condition that's usually inherited. It's often first detected in children and young adults. LQTS also may be acquired, rather than inherited, and caused by certain medicines and conditions.
• Faulty genes that control the production of certain types of ion channels in your heart cells cause inherited LQTS. The faulty ion channels interfere with the normal flow of sodium and potassium ions into and out of the cells during a heartbeat. The abnormal flow may disrupt the timing of the electrical activity in the heart and lead to dangerous heart rhythms.
• If you have LQTS, you're prone to developing a sudden and dangerous arrhythmia in response to certain conditions. The signs and symptoms of LQTS-related arrhythmias include unexplained fainting or seizures, drowning or near drowning (due to fainting while swimming), sudden cardiac arrest, and sudden death.
• Some people who have LQTS have no signs or symptoms. This condition is called silent LQTS.
• To diagnose LQTS, your doctor will consider your EKG (electrocardiogram) results, your personal and family medical histories, and genetic test results.
• Treatments for LQTS include lifestyle changes, medicines, implanted medical devices, and surgery to regulate your heartbeat. Treatment isn't a cure for the condition, but it does greatly improve survival.
• If you have LQTS, you will need to take certain steps for the rest of your life to prevent an abnormal heartbeat and to ensure that you get treatment right away if one occurs.
• Avoid things that trigger an abnormal heartbeat, such as exercise or certain medicines. Let the people whom you see regularly know about your LQTS. Ask them to call 9–1–1 right away if you faint. Have a plan in place for when you develop and abnormal heartbeat.
• See your cardiologist (heart specialist) regularly. He or she will adjust your treatment as needed.