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. (Visit the Diseases and Conditions
Index
How
the Heart Works article for more information on the heart's electrical
system.)
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:
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:
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. (For more
information, go to
"What
Causes Long QT Syndrome?")
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.
Links to Other Information About Long QT
Syndrome
NHLBI Resources
Non-NHLBI Resources
Clinical Trials
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