What Is Long QT Syndrome?
Long QT syndrome (LQTS) is a disorder of the heart's
electrical activity that may cause you to develop a sudden, uncontrollable, and
dangerous heart rhythm (called an
arrhythmia)
in response to exercise or stress. Such abnormal heart rhythms also can develop
for no known reason in people who have LQTS. Not everyone who has LQTS develops
a dangerous heart rhythm, but if one does occur, it may be fatal.
The term "long QT" refers to an abnormality seen on
an EKG
(electrocardiogram). An EKG is a test that detects and records the electrical
activity of the heart. The QT interval, recorded on the EKG, corresponds to the
time during which the lower chambers of your heart (the ventricles) are
triggered to contract and then build the potential to contract again.
The timing of the electrical activity of the
heartbeat is complex and carefully controlled by the body. Normally the QT
interval of the heartbeat lasts about a third of each heartbeat cycle on the
EKG. But in people with LQTS, the QT interval usually lasts longer than normal,
which can upset the careful timing of the heartbeat and trigger a dangerous,
irregular 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 electrical activity of the heart.
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 to allow 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. (See
the Diseases and Conditions Index article on
How
the Heart Works 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
are 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 physical exercise (especially
swimming) that makes the heart beat faster tends to trigger irregular heart
rhythms if you have LQTS 1. In LQTS 2, irregular rhythms may be triggered
by surprise or other extreme emotions. In LQTS 3, a low heart rate during sleep
may be the trigger for an irregular heart rhythm.
Acquired, or noninherited, LQTS may be brought on by
certain medicines and other medical conditions.
Outlook
More than half the people who have an untreated,
inherited form of LQTS die within 10 years. But for many people with LQTS,
lifestyle changes and medical treatments can help prevent dangerous
complications and lengthen life expectancy. Some of these changes 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 implantable device, such as a pacemaker
or implantable cardioverter defibrillator, that helps control abnormal heart
rhythms
Discuss with your doctor the lifestyle changes and
treatments that 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 that control the production of certain
types of ion channels in your heart cells cause inherited long QT syndrome
(LQTS). These LQTS genes may cause the body to produce too few ion channels or
ion channels that don't work as they should, 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 LQTS types stem from faulty or lacking potassium ion channels, while
others are due to faulty or lacking sodium channels.
If you have LQTS 1 and LQTS 2, the flow of potassium
ions through the ion channels in your heart cells isn't normal, which 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 may prevent 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, which also may trigger a rapid
and uncontrollable heart rhythm that can result in death. In LQTS 3, problems
usually develop when your heart beats slower than normal, such as during sleep.
Noninherited Long QT Syndrome
Acquired, or noninherited, LQTS may be brought on by
certain medicines and other medical conditions. Side effects from certain
medicines are the most common cause of 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 with medication-induced LQTS may also
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. This is sometimes 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?
Populations Affected
Long QT syndrome (LQTS) is a rare condition. Experts
suspect 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 with LQTS experience their
first irregular heartbeat by the time they're 12 years old, and 90 percent by
the time they reach 40 years old. Rarely is inherited LQTS first diagnosed in
someone after age 40. In boys with LQTS, the QT interval often returns toward
normal after puberty, and the risk of fainting and
sudden
cardiac arrest decreases.
LQTS is more common in women than men. Women who
have LQTS are more likely to experience fainting or sudden death from the
condition during menstruation and shortly after giving birth. LQTS also is
common in children born deaf. This is because the same genetic abnormality that
affects hearing also affects the working 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 (on your
EKG)
longer. Your doctor can tell you whether the 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 disorder anorexia nervosa 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.
Symptoms or signs of the arrhythmias that people with LQTS tend to have 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 a fluttering feeling
in their chest before they faint.
- Unexplained seizures. Those around you may
mistake your fainting from LQTS to be 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 or death. This means that your heart suddenly stops beating
for no obvious reason. People who have sudden cardiac arrest will die within
minutes unless they receive treatment. Most people who experience sudden
cardiac arrest die. In about 1 out of 10 patients, sudden cardiac arrest or
death is the first sign of LQTS.
Other Signs and Symptoms
Often people with LQTS 3 will develop an irregular
heartbeat during sleep. This may cause them to have noisy gasping while
sleeping.
How Is Long QT Syndrome Diagnosed?
Doctors' Considerations
Doctors called cardiologists diagnose and treat long
QT syndrome (LQTS). Cardiologists are doctors who specialize in treating
problems and diseases of the heart. 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
electrical activity of the heart. This test may reveal a long QT interval and
other signs that make it more likely that you have LQTS. Often your doctor
first discovers you have a long QT interval when an EKG is done for another
suspected heart problem.
Not all people with LQTS will always have a long QT
interval on an EKG. The QT interval may change from time to time, sometimes
being long and other times normal. Because of this, your doctor may want you to
have several EKG tests over a period of days or weeks. Or your doctor will have
you wear a device called a Holter monitor.
A Holter monitor, also called an ambulatory EKG,
records the electrical activity of your heart for a full 24-hour period. For
this test, you wear patches called electrodes on your chest that are connected
by wires to a small, portable recorder. The recorder may be clipped to a belt,
kept in a pocket, or hung around your neck. During the 24 hours, you do your
usual daily activities. You then return the recorder to the doctor to read the
results. The purpose of a Holter monitor EKG 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 an exercise
stress
test.
For this test, a machine records your EKG while you
exercise. If you're unable to exercise, a medicine may be injected through an
intravenous line into your bloodstream to make your heart work harder and beat
faster as if you were exercising.
Medical History and Physical Exam
Your doctor will ask whether you have had any
symptoms of an irregular heartbeat. These 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 will ask what over-the-counter,
prescription, or recreational drugs you take.
Your doctor also will want to know whether anyone in
your family was 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 will look for the
presence of conditions that may lower blood levels of potassium or sodium.
These conditions include the eating disorder anorexia nervosa, 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 are usually also suggested for
family members of people with LQTS. But about one-third of LQTS cases aren't
detected with genetic testing. Even if you do 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. Fewer than 1 out of 10 of these people will
faint or suddenly die from an irregular heartbeat.
But even if you have silent LQTS, you may be more at
risk than most people for developing an irregular 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. That way, you
and your doctor can better target the treatment and lifestyle measures you need
to take. To figure out your LQTS type, your doctor will consider:
- Genetic test results
- The types of situations that trigger an irregular
heartbeat
- How well you respond to medicine
How Is Long QT Syndrome Treated?
Goals of Treatment
The goal of treating long QT syndrome (LQTS) is to
prevent life-threatening, irregular heartbeats and fainting spells. Treatment
isn't a cure for this condition and may not restore a long QT interval (on your
EKG)
to normal. But it does greatly improve survival.
Specific Types of Treatment
Your doctor will recommend the best treatment for
you based on:
- What type of LQTS you have
- How likely it is that you will faint or that your
heart will suddenly stop beating
- What treatment you feel most comfortable taking
People who have a lower risk of complications from
LQTS may want to try less aggressive treatments, such as making lifestyle
changes (avoiding situations that trigger irregular heartbeats) or taking
medicines. The type of LQTS you have will determine which medicines you take to
avoid abnormal heart rhythms. For example, doctors will usually only prescribe
sodium channel blocker medicines for people with LQTS 3.
If your doctor thinks you're at higher risk for
complications from your LQTS, he or she may recommend 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)) that helps regulate
your heartbeat
- Surgery on the nerves that regulate your
heartbeat
Patients 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 irregular heartbeat. Many
people with LQTS also benefit from adding more potassium to their diets. They
should check with their doctor about eating more potassium-rich foods, such as
bananas, or taking potassium supplements daily.
People with LQTS also should avoid medicines that
lengthen the QT interval or lower potassium blood levels. (See "What Causes Long QT Syndrome?")
Medicines
Beta blocker heart medicines prevent the heart from
beating faster in response to physical or emotional stress. Most people with
LQTS are treated with beta blockers. Doctors may suggest that people with LQTS
3 take sodium channel blocker medicines, such as mexiletine. These make sodium
ion channels less active.
Pacemaker or Implantable Cardioverter Defibrillator
These are surgically implanted devices that monitor
the heart rhythm and 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 at high risk of death from LQTS are sometimes
treated with surgery in which the nerves that prompt the heart to beat faster
in response to physical or emotional stress are cut. This helps to 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) is usually a lifelong
condition. The risk of developing an irregular heartbeat that leads to fainting
or sudden
cardiac arrest may lessen as you age, but the risk never disappears. You
need to take certain steps for the rest of your life to prevent an irregular
heartbeat or to ensure that you get immediate treatment 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
irregular heartbeat
Avoid Triggers
If exercise triggers an irregular heartbeat, your
doctor may recommend that you avoid any strenuous exercise, especially
swimming. Ask your doctor which types of exercise are right for you. If you
have a pacemaker or implantable cardioverter defibrillator you will need to
avoid contact sports that may dislodge these devices. You may want to only
exercise in public or with a friend who will help you if you faint.
Avoid medicines that may trigger an irregular
heartbeat. These medicines include those used to treat allergies, infections,
high
blood pressure,
high
cholesterol, and depression. Consult with your doctor before you take any
prescription, over-the-counter, or other drugs.
Seek medical care immediately for conditions that
lower the potassium level in your blood. These conditions include excessive
diarrhea, vomiting, or the eating disorder anorexia nervosa.
Avoid unexpected noises in your bedroom if you have
LQTS 2. These noises include loud or jarring alarm clock buzzers and
telephone ringers.
Inform Others
You may want to consider wearing a medical
identification 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.
Let these people know that they should get you emergency medical care
immediately if you faint.
You may want to have someone in your family or
office learn cardiopulmonary resuscitation (CPR) in case your heart stops
beating. You also could 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 work should be trained 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
irregular heartbeat while lying down.
Ongoing Health Care Needs
You should see your cardiologist 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.
It can be stressful to have LQTS, or to have a
family member with it. You may want to ask your doctor to recommend a LQTS
support group.
Key Points
- Long QT syndrome (LQTS) is a disorder of the
heart's electrical activity.
- If you have LQTS, your heart is more likely to
develop a sudden, uncontrollable, and dangerous heart rhythm (called an
arrhythmia)
in response to exercise, stress, or other conditions.
- This abnormal heart rhythm makes you prone to
fainting or to
sudden
cardiac arrest because your heart stops beating.
- 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
disorders.
- Faulty genes that control the production of
certain types of ion channels in your heart cells cause inherited long QT
syndrome (LQTS). The faulty ion channels interfere with the normal flow of
sodium and potassium atoms 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.
- For many people who have LQTS, lifestyle changes
and medical treatments may help prevent dangerous complications.
- If you have LQTS, you're prone to developing a
sudden and dangerous arrhythmia in response to certain conditions. The signs
and symptoms of arrhythmias that people with LQTS tend to have include
unexplained fainting or seizures, drowning or near drowning (due to fainting
while swimming), sudden cardiac arrest, and sudden death.
- To diagnose LQTS, your doctor will consider your
EKG
(electrocardiogram) results, your personal and family medical history, and
genetic test results.
- Treatments for LQTS include lifestyle changes,
medicines, implanted medical devices, and surgery to regulate your heartbeat.
- You should let the people whom you see regularly
know about your condition. Ask them to immediately call emergency medical
services if you faint.
- See your cardiologist 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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