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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 if rapid, disorganized electrical signals cause the heart's two upper chambers—called the atria (AY-tree-uh)—to fibrillate. The term "fibrillate" means to contract very fast and irregularly.
In AF, blood pools in the atria. It isn't pumped completely into the heart's two lower chambers, called the ventricles (VEN-trih-kuls). As a result, the heart's upper and lower chambers don't work together as they should.
People who have AF may not feel symptoms. However, even when AF isn't noticed, it can increase the risk of stroke. In some people, AF can cause chest pain or heart failure, especially if the heart rhythm is very rapid.
AF may happen rarely or every now and then, or it may become an ongoing or long-term heart problem that lasts for years.
To understand arrhythmias, 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.
Each electrical signal begins in a group of cells called the sinus node or sinoatrial (SA) node. The SA node is located in the heart's upper right chamber, the right atrium (AY-tree-um). 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.
From the SA node, the electrical signal travels through special pathways in the right and left atria. This causes the atria to contract and pump blood into the heart's two lower chambers, the ventricles (VEN-trih-kuls).
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 along a pathway called the bundle of His. This pathway divides into a right bundle branch and a left bundle branch. The signal goes down these branches to the ventricles, causing them to contract and pump blood 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.
A problem with any part of this process can cause an arrhythmia. For example, in atrial fibrillation (A-tre-al fi-bri-LA-shun), a common type of arrhythmia, electrical signals travel through the atria in a fast and disorganized way. This causes the atria to quiver instead of contract.
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. They may spread throughout the atria in a rapid, disorganized way. This can cause the atria to fibrillate.
The faulty 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 send the signals to the ventricles as fast as they arrive. So, even though the ventricles are 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.
If 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 random 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 ongoing and require treatment. Sometimes AF is permanent, and medicines or other treatments can't restore a normal heart rhythm.
Atrial fibrillation (AF) usually causes the heart's lower chambers, the ventricles, to contract faster than normal.
When this happens, the ventricles can't completely fill with blood. Thus, they may not be able to pump enough blood to the lungs and body. This can lead to signs and symptoms, such as:
- Palpitations (feeling that your heart is skipping a beat, fluttering, or beating too hard or fast)
- Shortness of breath
- Weakness or problems exercising
- Chest pain
- Dizziness or fainting
- Fatique (tiredness)
- Atrial Fibrillation Complications
StrokeDuring AF, the heart's upper chambers, 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 that reduce the risk of stroke are an important part of treatment for people who have AF.
Heart FailureHeart failure occurs if 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 can't completely fill with blood. Thus, they may not be able to pump enough blood to the lungs and 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 procedures or surgery (rarely, a mechanical heart pump or heart transplant) are the main treatments for heart failure.
Treatment for atrial fibrillation (AF) depends on how often you have symptoms, how severe they are, and whether you already have heart disease. General treatment options include medicines, medical procedures, and lifestyle changes.
Goals of TreatmentThe goals of treating AF include:
- Preventing blood clots from forming, thus lowering the risks of stroke
- Controlling how many times aminute the ventricles contract. This is called rate control. Rate controlis important because it allows the ventricles enough time to completely fill with blood. With this approach, the abnormal heart rhythm continues, but you feel better and 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 causing that's causing or raising the risk of AF - for example, hyperthyoidism (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 a normal heart rhythm.
Repeat 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 rate and prevent complications.
Specific Types of Treatment
Blood Clot PreventionPeople who have AF are at increased risk for stroke. This is because blood can pool in the heart's upper chambers (the atria), causing a blood clot to form. If the clot breaks off and travels to the brain, it can cause a stroke.
Preventing blood clots from forming is probably the most important part of treating AF. The benefits of this type of treatment have been proven in multiple studies.
Doctors prescribe blood-thinning medicines to prevent blood clots. These medicines include warfarin (Coumadin®), dabigatran, heparin, and aspirin.
People taking blood-thinning medicines need regular blood tests to check how well the medicines are working.
Rate ControlDoctors can 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 ControlRestoring and maintaining a normal heart rhythm is a treatment approach recommended for people who aren't doing well with rate control treatment. This treatment also may be used for people who have only recently started having AF. The long-term benefits of rhythm control have not been proven conclusively yet.
Doctors use medicines or procedures to control the heart's rhythm. Patients often begin rhythm control treatment in a hospital so that their hearts can be closely watched.
The longer you have AF, the less likely it is that doctors can restore 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 are enlarged or if any underlying heart disease worsens. 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.
MedicationMedicines used to control the heart rhythm include amiodarone, sotalol, flecainide, propafenone, dofetilide, and ibutilide. Sometimes 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.
These medicines also can harm people who have underlying diseases of the heart or other organs. This is especially 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 repeat episodes.
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.
ProceduresDoctors use several procedures to restore a normal heart rhythm. For example, they may use electrical cardioversion to treat a fast or irregular heartbeat. For this procedure, low-energy shocks are given to your heart to trigger a normal rhythm. You're temporarily put to sleep before you receive the shocks.
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). This test can rule out the presence of blood clots in the atria. If clots are present, you may need to take blood-thinning medicines before the procedure. These medicines can help get rid of the clots.
Catheter ablation (ab-LA-shun) may be used to restore a normal heart rhythm if medicines or electrical cardioversion don't work. For 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. Your doctor may recommend a TEE before catheter ablation to check for blood clots in the atria.
Sometimes doctors use catheter ablation to destroy the atrioventricular (AV) node. The AV node is where the heart's electrical signals pass from the atria to the ventricles (the heart's lower chambers). This procedure requires your doctor to surgically implant a device called a pacemaker, which helps maintain a normal heart rhythm.
Research on 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. For this procedure, the surgeon makes small cuts or burns in the atria. These cuts or burns 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 heart valve disease (which can increase the risk of AF).
Approaches To Treating Underlying Causes and Reducing Risk FactorsYour doctor may recommend treatments for an underlying cause of AF or to reduce AF risk factors. For example, he or she may prescribe medicines to treat an overactive thyroid, lower high blood pressure, or manage high blood cholesterol.
Your doctor also may recommend lifestyle changes, such as following a healthy diet, cutting back on salt intake (to help lower blood pressure), quitting smoking, and reducing stress.
Limiting or avoiding alcohol, caffeine, or other stimulants that may increase your heart rate also can help reduce your risk for AF.