Atrial fibrillation (A-tre-al fi-bri-LA-shun), or
AF, is the most common type of
arrhythmia
(ah-RITH-me-ah). An arrhythmia is a problem with the rate or rhythm of the
heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or with
an irregular rhythm.
AF occurs when rapid, disorganized electrical
signals cause the atria (AY-tree-uh), the two upper chambers of the heart, to
fibrillate. The term "fibrillate" means to contract very fast and irregularly.
In AF, blood pools in the atria and isn't pumped
completely into the ventricles (VEN-trih-kuls), the heart's two lower chambers.
As a result, the heart's upper and lower chambers don't work together as they
should.
Often, people who have AF may not feel symptoms.
However, even when not noticed, AF can increase the risk of
stroke. In some people, AF can cause chest pain or
heart
failure, particularly when the heart rhythm is very rapid.
AF may occur rarely or every now and then, or it may
become a persistent or permanent heart rhythm lasting for years.
Understanding the Heart's Electrical System
To understand AF, it helps to understand the heart's
internal electrical system. The heart's electrical system controls the rate and
rhythm of the heartbeat.
With each heartbeat, an electrical signal spreads
from the top of the heart to the bottom. As the signal travels, it causes the
heart to contract and pump blood. The process repeats with each new heartbeat.
Each electrical signal begins in a group of cells
called the sinus node or sinoatrial (SA) node. The SA node is located in the
right atrium. In a healthy adult heart at rest, the SA node fires off an
electrical signal to begin a new heartbeat 60 to 100 times a minute. (This rate
may be slower in very fit athletes.)
From the SA node, the electrical signal travels
through the right and left atria. This causes the atria to contract and pump
blood into the ventricles.
The electrical signal then moves down to a group of
cells called the atrioventricular (AV) node, located between the atria and the
ventricles. Here, the signal slows down just a little, allowing the ventricles
time to finish filling with blood.
The electrical signal then leaves the AV node and
travels to the ventricles. This causes the ventricles to contract and pump
blood out to the lungs and the rest of the body. The ventricles then relax, and
the heartbeat process starts all over again in the SA node.
For more information on the heart's electrical
system and detailed animations, go to the Diseases and Conditions Index
How
the Heart Works article.
Understanding the Electrical Problem in Atrial
Fibrillation
In AF, the heart's electrical signals don't begin in
the SA node. Instead, they begin in another part of the atria or in the nearby
pulmonary veins. The signals don't travel normally, and they may spread
throughout the atria in a rapid, disorganized way. This can cause the atria to
fibrillate.
The abnormal electrical signals flood the AV node
with electrical impulses. As a result, the ventricles also begin to beat very
fast. However, the AV node can't conduct the signals to the ventricles as fast
as they arrive. So, even though the ventricles may be beating faster than
normal, they aren't beating as fast as the atria.
Thus, the atria and ventricles no longer beat in a
coordinated way. This creates a fast and irregular heart rhythm. In AF, the
ventricles may beat 100 to 175 times a minute, in contrast to the normal rate
of 60 to 100 beats a minute.
When this happens, blood isn't pumped into the
ventricles as well as it should be. Also, the amount of blood pumped out of the
ventricles to the body is based on the randomness of the atrial beats.
The body may get rapid, small amounts of blood and
occasional larger amounts of blood. The amount will depend on how much blood
has flowed from the atria to the ventricles with each beat.
Most of the symptoms of AF are related to how fast
the heart is beating. If medicines or age slow the heart rate, the symptoms are
minimized.
AF may be brief, with symptoms that come and go and
end on their own. Or, the condition may be persistent and require treatment.
Sometimes AF is permanent, and medicines or other treatments can't restore a
normal heart rhythm.
The animation below shows atrial fibrillation. Click
the "start" button to play the animation. Written and spoken explanations are
provided with each frame. Use the buttons in the lower right corner to pause,
restart, or replay the animation, or use the scroll bar below the buttons to
move through the frames.
The animation shows how the heart's
electrical signal begins in a place other than the sinoatrial node, causing the
atria to beat very fast and irregularly.
Outlook
People who have AF can live normal, active lives.
For some people, treatment can cure AF and restore normal heart rhythms.
For people who have permanent AF, treatment can
successfully control symptoms and prevent complications. Treatments include
medicines, medical procedures, and lifestyle changes.
Types of Atrial Fibrillation
Paroxysmal Atrial Fibrillation
In paroxysmal (par-ok-SIZ-mal) atrial fibrillation
(AF), the abnormal electrical signals and rapid heart rate begin suddenly and
then stop on their own. Symptoms can be mild or severe and last for seconds,
minutes, hours, or days.
Persistent Atrial Fibrillation
Persistent AF is a condition in which the abnormal
heart rhythm continues until it's stopped with treatment.
Permanent Atrial Fibrillation
Permanent AF is a condition in which a normal heart
rhythm can't be restored with the usual treatments. Both paroxysmal and
persistent AF may become more frequent and, over time, result in permanent AF.
Other Names for Atrial Fibrillation
A fib
Auricular fibrillation
What Causes Atrial Fibrillation?
Atrial fibrillation (AF) occurs when the electrical
signals traveling through the heart are conducted abnormally and become very
rapid and disorganized.
This is the result of damage to the heart's
electrical system. The damage most often is the result of other conditions,
such as
coronary
heart disease (also called coronary artery disease) or
high
blood pressure, that affect the health of the heart.
Sometimes, the cause of AF is unknown.
Who Is At Risk for Atrial Fibrillation?
More than 2 million people in the United States have
atrial fibrillation (AF). It affects both men and women.
The risk of AF increases as you age. This is mostly
because as you get older, your risk for heart disease and other conditions that
can cause AF also increases. However, about half of the people who have AF are
younger than 75.
AF is uncommon in children.
Major Risk Factors
AF is more common in people who have heart diseases
or conditions, such as:
Sick sinus syndrome (a condition in which the
heart's electrical signals don't fire properly and the heart rate slows down;
sometimes the heart will switch back and forth between a slow rate and a fast
rate)
AF also is more common in people who are having
heart
attacks or who have just had surgery.
Other Risk Factors
Other conditions that increase AF risk include
hyperthyroidism (too much thyroid hormone),
obesity,
high
blood pressure, diabetes, and lung disease.
Other factors also can increase your risk of AF. For
example, drinking large amounts of alcohol, especially binge drinking,
increases your risk. Even modest amounts of alcohol can trigger AF in some
people. Caffeine or psychological stress also may trigger AF in some people.
Some evidence suggests that people who have
sleep
apnea are at greater risk for AF. Sleep apnea is a common disorder in which
you have one or more pauses in breathing or shallow breaths while you
sleep.
Metabolic
syndrome also increases your risk of AF. People who have this condition
have a group of risk factors that increase their risk of heart disease and
other health problems.
Recent research suggests that people who receive
high-dose steroid therapy are at increased risk of AF. This therapy, which is
commonly used for
asthma
and certain inflammatory conditions, may act as a trigger in people who already
have other AF risk factors.
What Are the Signs and Symptoms of Atrial
Fibrillation?
Atrial fibrillation (AF) usually causes the
ventricles to contract faster than normal. When this happens, the ventricles
don't have enough time to fill completely with blood to pump to the lungs and
body.
This inefficient pumping can cause signs and
symptoms, such as:
Palpitations
(feelings that your heart is skipping a beat, fluttering, or beating too hard
or fast)
During AF, the atria don't pump all of their blood
to the ventricles. Some blood pools in the atria. When this happens, a blood
clot (also called a thrombus) can form.
If the clot breaks off and travels to the brain, it
can cause a stroke. (A clot that forms in one part of the body and travels in
the bloodstream to another part of the body is called an embolus.)
Blood-thinning medicines to reduce the risk of
stroke are a very important part of treatment for people who have AF.
Atrial Fibrillation and Stroke
The illustration shows how a stroke
can occur during atrial fibrillation. If a clot (thrombus) forms in the left
atrium of the heart, a piece of it can dislodge and travel to an artery in the
brain, blocking blood flow through the artery. The lack of blood flow to the
portion of the brain fed by the artery causes a stroke.
Heart Failure
Heart failure occurs when the heart can't pump
enough blood to meet the body's needs. AF can lead to heart failure because the
ventricles are beating very fast and aren't able to properly fill with blood to
pump out to the body.
Fatigue and shortness of breath are common symptoms
of heart failure. A buildup of fluid in the lungs causes these symptoms. Fluid
also can build up in the feet, ankles, and legs, causing weight gain.
Lifestyle changes, medicines, and sometimes special
care (rarely, a mechanical heart pump or
heart
transplant) are the main treatments for heart failure.
How Is Atrial Fibrillation Diagnosed?
Some people who have atrial fibrillation (AF) don't
have symptoms. For these people, AF often is found during a physical exam or
EKG
(electrocardiogram) test done for another purpose. Other times, AF is diagnosed
after a person goes to the doctor because of symptoms.
To understand why a person has AF and the best way
to treat it, the doctor will want to find any immediate or underlying causes of
the condition.
Doctors use several methods to diagnose AF,
including taking medical and family histories, doing a physical exam, and doing
several tests and procedures.
Specialists Involved
A primary care doctor often is involved in the
initial diagnosis and treatment of AF. These doctors can include family
practitioners and internists.
Doctors who specialize in the diagnosis and
treatment of heart disease also may be involved, such as:
Cardiologists. These are doctors who diagnose
and treat heart diseases and conditions.
Electrophysiologists. These are cardiologists
who specialize in
arrhythmias.
Medical and Family Histories
Your doctor will ask questions about your:
Signs and symptoms. What symptoms are you
having? Have you had
palpitations?
Are you dizzy or short of breath? Are your feet or ankles swollen (a possible
sign of
heart
failure)? Do you have any chest pain?
Medical history. This includes other health
problems, such as a history of
heart
disease,
high
blood pressure, lung disease, diabetes, or thyroid problems.
Family's medical history. Does anyone in your
family have a history of AF? Has anyone in your family ever had heart disease
or high blood pressure? Has anyone had thyroid problems? Are there other
illnesses or health problems in your family?
Health habits. Your doctor may ask whether you
smoke or use alcohol or caffeine.
Physical Exam
Your doctor will do a complete cardiac exam,
listening to the rate and rhythm of your heartbeat and taking your pulse and
blood pressure reading. He or she will likely check to see whether you have any
signs of heart muscle or valve problems. Your doctor will listen to your lungs
to check for signs of heart failure.
Your doctor also will check for swelling in your
legs or feet and look for an enlarged thyroid gland or other signs of
hyperthyroidism (too much thyroid hormone).
Diagnostic Tests and Procedures
EKG
An EKG is a simple, painless test that records the
heart's electrical activity. It's the most useful test for diagnosing AF.
An EKG shows how fast your heart is beating and its
rhythm (steady or irregular). It also records the strength and timing of
electrical signals as they pass through each part of your heart.
A standard EKG only records the heartbeat for a few
seconds. It won't detect an AF episode that doesn't happen during the test. To
diagnose paroxysmal AF, your doctor may ask you to wear a portable EKG monitor
that can record your heartbeat for longer periods.
A Holter monitor records the heart's
electrical activity for a full 24- or 48-hour period. You wear small patches
called electrodes on your chest. These patches 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.
You wear the Holter monitor while you do your normal
daily activities. This allows the monitor to record your heart for a longer
time than a standard EKG.
An event monitor is similar to a Holter monitor. You
wear an event monitor while doing your normal activities. However, an event
monitor only records your heart's electrical activity at certain times while
you're wearing it.
For many event monitors, you push a button to start
the monitor when you feel symptoms. Other event monitors start automatically
when they sense abnormal heart rhythms.
You might wear an event monitor for 1 to 2 months,
or as long as it takes to get a recording of your heart during symptoms.
Stress Test
Some heart problems are easier to diagnose when your
heart is working hard and beating fast. During
stress
testing, you exercise (or are given medicine if you're unable to exercise)
to make your heart work hard and beat fast while heart tests are done.
Echocardiography
Echocardiography
(echo) uses sound waves to create a moving picture of your heart. The test
provides information about the size and shape of your heart and how well your
heart chambers and valves are working.
Echo also can identify areas of poor blood flow to
the heart, areas of heart muscle that aren't contracting normally, and previous
injury to the heart muscle caused by poor blood flow.
This test is sometimes called transthoracic
(trans-thor-AS-ik) echocardiography. It's painless and noninvasive (no
instruments are inserted into the body). The test is done by placing a device
called a transducer on your chest. The device sends special sound waves through
your chest wall to your heart.
The sound waves bounce off the structures of your
heart, and a computer converts them into pictures on a screen.
Transesophageal Echocardiography
Transesophageal (trans-e-SOF-ah-ge-al) echo, or TEE,
takes pictures of your heart through the esophagus (the passage leading from
your mouth to your stomach).
The atria are deep in your chest and often can't be
seen very well using transthoracic echo. Your doctor can see the atria much
better using TEE.
During this test, the transducer is attached to the
end of a flexible tube that's guided down your throat and into your esophagus.
You'll probably be given medicine to help you relax during the procedure. TEE
is used to detect blood clots that may be developing in the atria because of
AF.
Chest X Ray
A
chest
x ray is a painless test that creates pictures of the structures in your
chest, such as your heart and lungs. This test can show fluid buildup in the
lungs and other complications of AF.
Blood Tests
Blood
tests check the level of thyroid hormone and the balance of your body's
electrolytes. Electrolytes are minerals that help maintain fluid levels and
acid-base balance in the body. They're essential for normal health and
functioning of your body's cells and organs.
How Is Atrial Fibrillation Treated?
Treatment for atrial fibrillation (AF) depends on
how severe or frequent the symptoms are and whether you already have heart
disease. General treatment options include medicines, medical procedures, and
lifestyle changes.
Goals of Treatment
The goals of treating AF include:
Preventing blood clots from forming, thereby
reducing the risk of stroke.
Controlling how many times a minute the
ventricles contract. This is called rate control. Rate control is important
because it allows the ventricles enough time to completely fill with blood.
With this approach, the irregular heart rhythm continues, but the person feels
better and has fewer symptoms.
Restoring a normal heart rhythm. This is called
rhythm control. Rhythm control allows the atria and ventricles to work together
to efficiently pump blood to the body.
Treating any underlying disorder that's causing
or raising the risk of AF—for example, hyperthyroidism (too much thyroid
hormone).
Who Needs Treatment for Atrial Fibrillation?
People who have AF but don't have symptoms or
related heart problems may not need treatment. AF may even go back to a normal
heart rhythm on its own. (This also can occur in people who have AF with
symptoms.)
In some people who have AF for the first time,
doctors may choose to use an electrical procedure or medicine to restore the
heart rhythm to normal.
Repeated episodes of AF tend to cause changes to the
heart's electrical system, leading to persistent or permanent AF. Most people
who have persistent or permanent AF need treatment to control their heart rates
and prevent complications.
Specific Types of Treatment
Blood Clot Prevention
The risk of a blood clot traveling from the heart to
the brain and causing a stroke is increased in people who have AF. Preventing
blood clots from forming is probably the most important part of treating AF.
Doctors prescribe blood-thinning medicines to
prevent blood clots. These medicines include warfarin
(Coumadin®), heparin, and aspirin.
Warfarin is the most effective medicine in people
who have risk factors for stroke. People taking warfarin must have regular
blood
tests to check how well the medicine is working.
Rate Control
Doctors prescribe medicines to slow down the rate at
which the ventricles are beating. These medicines help bring the heart rate to
a normal level.
Rate control is the recommended treatment for most
patients who have AF, even though an abnormal heart rhythm continues and the
heart doesn't work as well as it should. Most people feel better and can
function well if their heart rates are well-controlled.
Medicines used to control the heart rate include
beta blockers (for example, metoprolol and atenolol), calcium channel blockers
(diltiazem and verapamil), and digitalis (digoxin). Several other medicines
also are available.
Rhythm Control
Doctors use medicines or procedures to restore and
maintain the heart's rhythm. This treatment approach is recommended for people
who aren't functioning well with rate control treatment or who have only
recently started having AF.
The longer you have AF, the less likely it is that
an abnormal heart rhythm can be restored to a normal heart rhythm. This is
especially true for people who have had AF for 6 months or more.
Restoring a normal rhythm also becomes less likely
if the atria become enlarged or if any underlying heart disease becomes more
severe. In these cases, the chance that AF will recur is high, even if you're
taking medicine to help convert AF to a normal rhythm.
Medicines. Medicines used to
control the heart rhythm include amiodarone, sotalol, flecainide, propafenone,
dofetilide, and ibutilide. Occasionally, older medicines, such as quinidine,
procainamide, and disopyramide, are used.
Your doctor will carefully tailor the dose and type
of medicines he or she prescribes to treat your AF. This is because medicines
used to treat AF can cause a different kind of
arrhythmia.
They also can harm people who have underlying diseases of the heart or other
organs. This is particularly true for patients who have an unusual heart rhythm
problem called
Wolff-Parkinson-White
syndrome.
Your doctor may start you on a small dose of
medicine and then gradually increase the dose until your symptoms are
controlled. Medicines used for rhythm control can be given regularly by
injection at a doctor's office, clinic, or hospital. Or, you may routinely take
pills to try to control AF or prevent recurrences.
If your doctor knows how you'll react to a medicine,
a specific dose may be prescribed for you to take on an as-needed basis if you
have an episode of AF.
Procedures. Doctors use several
procedures to restore a normal heart rhythm. Electrical
cardioversion
is a procedure used to restore a fast or irregular heartbeat to a normal
rhythm. For the procedure, low-energy shocks are given to your heart to trigger
a normal rhythm. You're temporarily put to sleep before the shocks are
given.
Electrical cardioversion isn't the same as the
emergency heart shocking procedure often seen on TV programs. It's planned in
advance and done under carefully controlled conditions.
Before doing electrical cardioversion, your doctor
may recommend
transesophageal
echocardiography (TEE) to rule out the presence of blood clots in the
atria. If clots are present, you may need to take blood-thinning medicines for
a period of time to help get rid of the clots before the procedure.
Catheter
ablation may be used to restore a normal heart rhythm when medicines or
electrical cardioversion don't work. During this procedure, a wire is inserted
through a vein in the leg or arm and threaded to the heart.
Radio wave energy is sent through the wire to
destroy abnormal tissue that may be disrupting the normal flow of electrical
signals. An electrophysiologist usually does this procedure in a hospital.
Sometimes catheter ablation is used to destroy the
atrioventricular (AV) node. The AV node is where the heart's electrical signals
pass from the atria to the ventricles. This procedure requires your doctor to
surgically implant a device called a
pacemaker
to maintain a normal heart rhythm.
Research to examine the benefits of catheter
ablation as a treatment for AF is still ongoing.
Another procedure to restore a normal heart rhythm
is called "maze" surgery. During this procedure, the surgeon makes small cuts
or burns in the atria that prevent the spread of disorganized electrical
signals.
This procedure requires
open-heart
surgery, so it's usually done when a person requires heart surgery for
other reasons, such as for valve disease (which can increase the risk of AF).
Approaches To Treating Underlying Causes and
Reducing Risk Factors
Your doctor also may recommend other treatments for
an underlying condition that may be causing AF or to reduce AF risk factors.
For example, he or she may prescribe medicines to treat an overactive thyroid
or reduce blood pressure.
Your doctor also may recommend lifestyle changes,
such as following a healthy diet, cutting back salt intake (to help lower blood
pressure), quitting smoking, and reducing stress.
Limiting or avoiding stress and alcohol, caffeine,
or other stimulants that may increase your heart rate also may help reduce the
risk of AF.
How Can Atrial Fibrillation Be Prevented?
You may be able to prevent atrial fibrillation (AF)
by following a healthy lifestyle and taking steps to lower your risk of heart
disease. These steps include:
Following a heart healthy diet that's low in
saturated fat, trans fat, and cholesterol. A healthy diet includes a
variety of whole grains, fruits, and vegetables daily.
Not smoking.
Getting physical activity regularly.
Maintaining a healthy weight.
If you have heart disease or other AF risk factors,
work with your doctor to control your condition and lower your risk of
complications, such as AF.
In addition to following the healthy lifestyle steps
above, which also can help control heart disease, your doctor may advise you to
take one or more of the following steps:
People who have atrial fibrillation (AF)—even
permanent AF—can live normal, active lives. If you have AF, ongoing
medical care is important.
Keep all your medical appointments. Bring all the
medicines you're taking to every doctor and emergency room visit. This will
help your doctor know exactly what medicines you're taking.
Follow your doctor's instructions for taking
medicines. Be careful about taking over-the-counter medicines, nutritional
supplements, and cold and allergy medicines. Some of these products contain
stimulants that can trigger rapid heart rhythms. Some over-the-counter
medicines can have harmful interactions with heart rhythm medicines.
Tell your doctor if your medicines are causing side
effects, if your symptoms are getting worse, or if you have new symptoms.
If you're taking blood-thinning medicines, you'll
need to be carefully monitored. For example, you may need regular
blood
tests to check how the medicines are working.
Talk with your doctor about diet, physical activity,
weight control, and alcohol use. Find out what steps you can take to manage
your condition.
Key Points
Atrial fibrillation (AF) is the most common type
of arrhythmia.
An arrhythmia is a problem with the rate or rhythm of the heartbeat.
AF occurs when rapid, disorganized electrical
signals cause the atria to fibrillate (contract very fast and irregularly).
When this happens, the heart's upper and lower chambers don't work together as
they should.
Often, people who have AF may not feel symptoms.
However, even when not noticed, AF can increase the risk of
stroke. In many people, AF can cause chest pain or
heart
failure, particularly when the heart rhythm is rapid.
The three types of AF are paroxysmal (the AF
comes and goes), persistent (the AF continues until stopped with treatment),
and permanent (a normal heart rhythm can't be restored).
Certain conditions, such as
coronary
heart disease or problems with the heart's structure, can lead to AF. Other
conditions, such as
obesity
and high
blood pressure, make it more likely that an episode of AF will happen.
More than 2 million people in the United States
have AF. It's affects both men and women. The risk of AF increases as you
age.
Signs and symptoms of AF include
palpitations,
shortness of breath, weakness or difficulty exercising, chest pain, dizziness
or fainting, fatigue (tiredness), or confusion.
AF has two major complications—stroke and
heart failure. In AF, blood pools in the atria and isn't pumped completely into
the ventricles. As a result, blood clots can form in the atria. A stroke can
occur if a blood clot in the atria breaks off and travels through the
bloodstream to the brain. Heart failure can occur because the heart isn't able
to function well and pump enough blood to the rest of the body.
Doctors diagnose AF using medical and family
histories, a physical exam, and tests and procedures. The most useful test for
diagnosing AF is an
EKG
(electrocardiogram).
Treatment for AF depends on how severe or
frequent the symptoms are and whether you already have heart disease. General
treatment options include medicines, medical procedures, and lifestyle changes.
You may be able to prevent AF by following a
heart healthy lifestyle and taking steps to lower your risk of heart disease,
such as following a healthy diet, not smoking, getting physical activity
regularly, and maintaining a healthy weight.
People who have AF can live normal, active
lives. For some people, treatment can cure AF and return their heartbeats to
normal rhythms. For people who have permanent AF, treatment can successfully
control symptoms and prevent complications.
Links to Other Information About Atrial
Fibrillation
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