Atrial Fibrillation

Atrial fibrillation describes a rapid, irregular heart rhythm. The irregular rhythm, or arrhythmia, results from abnormal electrical impulses in the heart. The irregularity can be continuous, or it can come and go.

The heart is a large muscle. Its function is to circulate (pump) blood through the body.

• The pump works by coordinated contractions of the 2 upper chambers of the heart (the atria) and the 2 lower chambers of the heart (the ventricles).
  
  
• A heartbeat comprises 2 contractions in quick succession. First, the atria receive blood returning to the heart and pump it into the ventricles; second, the ventricles pump blood out of the heart, either to the lungs from the right ventricle to take up fresh oxygen or out into the circulatory system of the body from the left ventricle.
  
  
• The circulatory system delivers oxygen- and nutrient-rich red, arterial blood from the heart to the body, and returns depleted blue, venous blood back to the heart.

Normal heart contractions begin as an electrical impulse in the right atrium. This impulse comes from an area of the atrium called the sinoatrial (SA) or sinus node, the "natural pacemaker."

• As the impulse travels through the atrium, it produces a wave of muscle contractions. This causes the atria to contract.
  
  
• The impulse reaches the atrioventricular (AV) node in the muscle wall between the 2 ventricles. There it pauses, giving blood from the atria time to enter the ventricles.
  
  
• The impulse then continues into the ventricles, causing a second ventricular contraction that pushes the blood out of the heart, completing a single heartbeat.
  
  

In a person with a normal heart rate and rhythm, this process is repeated 60-100 times per minute.

• If the heart beats more than 100 times per minute, the heart rate is considered fast (tachycardia).
  
  
• If the heart beats less than 60 times per minute, the heart rate is considered slow (bradycardia).
  
  

In atrial fibrillation, multiple impulses travel through the atria at the same time.

• Instead of a coordinated contraction, the contractions are irregular, disorganized, chaotic, or fibrillating and very rapid. The atria contracts at a rate of 400-600 per minute.
  
  
• These irregular impulses reach the ventricles in rapid succession, but not all of them make it past the AV node, which only lets about 110-180 beats per minute through to the ventricles, but still faster than normal.
  
  
• The resulting chaotic heartbeat causes an irregular pulse and sometimes a sensation of fluttering in the chest.
  
  

Atrial fibrillation can occur in several different patterns.

• Intermittent (paroxysmal): The heart "converts" spontaneously from normal (sinus) rhythm to atrial fibrillation and typically converts back again spontaneously. The episodes may last anywhere from seconds to minutes to hours.
  
  
• Persistent: Atrial fibrillation occurs in episodes, but the arrhythmia does not convert back to sinus rhythm spontaneously; it may last days to weeks, even a couple of months. Medical or electrical treatment may be needed to end the episode.
  
  
• Permanent: The heart is always in atrial fibrillation. Conversion back to sinus rhythm either is not possible or is deemed not appropriate for medical reasons.
  
  

Atrial fibrillation, often called "A Fib," is the most common pathologic heart rhythm disorder.

• It affects about 1% of the population, mostly people older than 50 years. This amounts to more than 2 million people.
  
  
• The risk of developing atrial fibrillation increases as we get older. About 5% of people older than 80 years have atrial fibrillation.
  
  

For many people, atrial fibrillation may cause symptoms but does no harm.

• Complications can arise, such as heart failure or stroke, but appropriate treatment reduces these risks.
  
  
• If treated properly, atrial fibrillation rarely causes serious or life-threatening problems. Only with serious underlying heart disease does atrial fib occasionally become life-threatening.
  
  
• Most people learn to live with their condition.
  
  

Primary or lone atrial fibrillation is atrial fibrillation without evidence of underlying heart disease. This is more common in younger people, about half of whom have no other heart problems. Some of the causes include the following:

• Hyperthyroidism (overactive thyroid)
  
  
• Pulmonary embolism (a blood clot in the blood vessels of the lung)
  
  
• Alcohol use

Secondary atrial fibrillation is caused by cardiac disease that affects the atria.

• Heart valve disease - This can be something you are born with or be caused by later disease or infection.
  
  
• Enlargement of the left ventricle walls (left ventricular hypertrophy)
  
  
• Coronary heart disease (or coronary artery disease) - This results from atherosclerosis, deposits of fatty material inside the arteries that cause blockage of the arteries, leading to heart damage/heart attack.
  
  
• High blood pressure (hypertension)
  
  
• Cardiomyopathy (disease of the heart muscle)
  
  
• Sick sinus syndrome (improper production of electrical impulses because of malfunction of the SA node)
  
  
• Pericarditis (inflammation of the sac surrounding the heart)
  
  

Atrial fibrillation sometimes occurs after cardiothoracic (open heart) surgery. This usually goes away by itself.

For many people with infrequent and brief episodes of atrial fibrillation, the episodes are brought on by a number of "triggers." Because many of these involve overindulgence, medical professionals sometimes call this "holiday heart." Some of these people are able to avoid episodes or have fewer episodes by avoiding their trigger. Common triggers include the following: 

• Alcohol use
  
  
• Caffeine
  
  
• Overeating
  
  

Symptoms of atrial fibrillation vary from person to person.

• Most people will feel unwell. A smaller number of people have no symptoms.
  
  
• The most common symptom in people with intermittent atrial fibrillation is palpitations, a sensation of very rapid heartbeat. This makes some people very anxious. People may feel that they are going to have a heart attack or die.
  
  
• Many people describe an irregular fluttering sensation in their chests.
  
  
• Some become light-headed or faint.
  
  
• Other symptoms include weakness, lack of energy or shortness of breath with effort, and chest pain.

Call for treatment within 48 hours if you have atrial fibrillation that comes and goes; have previously been evaluated and treated; and are not experiencing chest pain, shortness of breath, weakness, or fainting.

Call if you have persistent atrial fibrillation while you are on medical therapy for the condition; you note worsening of your new symptoms; or new symptoms, such as fatigue or mild shortness of breath, occur.

Call if you have questions about medications and dosages.

Call 911 for emergency medical services when atrial fibrillation occurs with any of the following:

• Severe shortness of breath
  
  
• Severe chest pain
  
  
• Fainting
  
  
• Severe weakness

Not all heart flutters are atrial fibrillation, but a continuing feeling of your heart fluttering in your chest together with a fast or slow pulse should be evaluated at a hospital emergency department.

In making the diagnosis, your health care provider will consider the severity of symptoms and whether they are new or have been going on for some time. You may be referred to a specialist in heart disorders (cardiologist) anytime during this evaluation. The evaluation may include the following tests:

Electrocardiogram (ECG): This is the primary test to determine when an arrhythmia is atrial fibrillation. The test also can reveal damage to the heart, if there is any.

Lab tests: No lab test can confirm that you have atrial fibrillation. Tests will be performed to check for certain underlying causes of atrial fibrillation and to rule out heart damage, as from a heart attack. If you are already taking medication for atrial fibrillation, a drug level may be checked to make sure there is enough of the drug in your system to work.

• Complete blood cell count
  
  
• Markers for heart injury
  
  
• Digoxin drug level
  
  
• Prothrombin time (PT) and international normalized ratio (INR) - If you are taking warfarin (Coumadin) to prevent blood clotting, these tests show how well the drug is working to lower your risk of a blood clot.
  
  
• Serum electrolytes to evaluate sodium and potassium levels
  
  
• Thyroid function tests for hyperthyroidism

Chest x-ray: This imagery is used to evaluate for complications such as fluid in the lungs or to estimate heart size

Echocardiogram: This is an ultrasound test that uses sound waves to make a picture of the inside of the heart while it is beating.

• This test is done to identify problems in heart valves or ventricular function or to look for blood clots in the atria.
  
  
• This is a very safe, painless test using the same technique used to check a fetus in pregnancy.
  
  
• This test is rarely done in an emergency department.
  
  

Ambulatory electrocardiogram (ECG): This test involves wearing a monitor, called a Holter monitor, for a period of time (usually 24-48 hours) to try to document the arrhythmia while you go about your everyday activities. This test may be used if your symptoms come and go and your ECGs do not reveal the arrhythmia.

Choice of treatment for atrial fibrillation depends on the type you have, the underlying cause, and your overall health. nbsp;

|Self-Care at Home|

There is no effective home treatment for atrial fibrillation.

• If your doctor recommends lifestyle changes or prescribes medicine, follow his or her recommendations exactly. This is the only way to see whether the treatment works.
  
  
• If it does not work, your health care provider wants to know so that he or she can prescribe a different treatment that might work better.
  
  
• Taking certain drugs (digoxin, warfarin) usually involves having your drug levels checked regularly until the correct dose is established.

|Medical Treatment|

Treatment has traditionally had 3 goals: to slow down the heart rate, to restore and maintain normal sinus rhythm, and to prevent stroke. Findings have recently come to light indicating that maintaining sinus rhythm saves no more lives than simply slowing down the heart rate, a much simpler goal.

• This is important because the medications used to maintain sinus rhythm have many more unwanted side effects and interactions with other drugs than the medications used to control rate. For example, an old drug, quinidine, caused an unexpected number of sudden cardiac deaths and is no longer used.
  
  
• The AFFIRM study, which was sponsored by the National Heart, Lung, and Blood Institute (part of the National Institutes of Health, the NIH), showed that maintaining sinus rhythm did not lower the risk of stroke, improve the quality of life, or improve mental function.
  
  
• People who took medication to maintain sinus rhythm had significantly more hospitalizations than people who received other treatments.
  
  
• The death rate from atrial fibrillation was the same in people who took rate-controlling medication as in people who took sinus rhythm-maintaining medication.
  
  
• In other words, slowing down the heart rate seems to work just as well as maintaining sinus rhythm and is a lot easier on the person being treated. Medical professionals are now considering each person individually to see whether maintaining sinus rhythm is worth the risk, effort, and expense for the patient.

Control ventricular rate: The first treatment goal is to slow down the ventricular rate.

• If you experience serious clinical symptoms, such as chest pain or congestive heart failure related to the fast ventricular rate, the health care provider in the emergency department will decrease your heart rate rapidly with IV medications or electrical shock (defibrillation).
  
  
• If you have no serious symptoms, you may be given medications by mouth. The most common drugs used are beta-blockers. Also used are calcium channel blockers and digoxin, the latter especially in patients with a poorly functioning left ventricle.
  
  
• Sometimes you may require a combination of oral medications to control your heart rate.
  
  
• Surgery may be done to control rate, but this is rare.
  
  

Anti-arrhythmic drugs used to restore and maintain normal sinus rhythm: About half the people with newly diagnosed atrial fibrillation will convert to normal sinus rhythm spontaneously in 24-48 hours. However, atrial fibrillation typically returns. The goal of treatment is to keep the sinus rhythm and prevent recurrent atrial fib.

• As already mentioned, not everyone with atrial fibrillation needs to take medication to maintain normal rhythm.
  
  
• The frequency with which your arrhythmia returns and the symptoms it causes partly determine whether you receive rhythm-controlling medication.
  
  
• Medical professionals tailor each person's anti-arrhythmia medication(s) carefully to produce the desired effect without causing side effects with a dose too high.
  
  
• Some of these medications cause unwanted, potentially life-threatening side effects, which limit their use.
  
  

Prevent stroke: Stroke is a devastating complication of atrial fibrillation. It occurs when a piece of a blood clot formed in the left atrium breaks off and travels to the brain, where it blocks blood flow.

• Coexisting medical conditions, such as coronary heart disease with atrial fibrillation, significantly increase the risk of stroke.
  
  
• Most people with atrial fibrillation take a blood-thinning drug called warfarin to lower this risk. Warfarin blocks a certain factor in the blood that promotes clotting.
  
  
• People at lower risk of stroke and those who cannot take warfarin may use aspirin. Aspirin is not without its own side effects, including bleeding problems and stomach ulcers.
  
  

Electrical defibrillation: This technique uses electrical current to "shock" the heart back to normal sinus rhythm. This is sometimes called "DC cardioversion."

• Two small handheld paddles are placed either on the front chest wall or on the front and back, underneath the left scapula, to deliver the "shock."
  
  
• This device is also used when the heart stops (this is familiar to watchers of television medical dramas).
  
  
• When this is done in a hospital, usually a mild, brief general anesthetic is given first, since the electrical shock is painful.
  
  
• Defibrillation works very well; more than 90% of people convert to sinus rhythm. For many, however, this is not a permanent solution because the atrial fib frequently comes back.
  
  
• Defibrillation increases the risk of stroke and thus requires pretreatment with an anticoagulant medication usually for 3 weeks before an elective cardioversion, and for 3 weeks following a successful conversion. The other choice is to perform a transesophageal echocardiogram. If the left atrium is clean (no clot), cardioversion can be done immediately, but 3 weeks of Coumadin will still be needed after the cardioversion.
  
  

Catheter ablation (radiofrequency ablation): "Ablation" means removal. This technique inactivates some of the abnormal conduction pathways in the atria.

• The abnormal pathway(s) is found, and a catheter is placed at this precise location in the conduction system.
  
  
• The catheter delivers radiofrequency energy that burns ("ablates") a portion of the abnormal electrical conduction pathways in the left atrium, frequently around the openings of the pulmonary veins. This inactivates the abnormal pathway to provide more consistent flow of electrical impulses.
  
  
• This technique is very safe; however, the procedure is new, some say still experimental, with unknown long-term success. It should only be performed in tertiary care centers with significant experience with this technique. When it does work, atrial fibrillation is cured. It has few complications and, unlike surgery, requires little recovery time.
  
  

Atrial pacemaker: A pacemaker is an electronic device that reduces the likelihood of atrial fibrillation episodes.

• The artificial pacemaker takes the place of the "natural pacemaker," the SA node, supplying electrical impulses to keep the heart beating in a normal rhythm when the SA node no longer can.
  
  
• The pacemaker battery or power source is implanted in the chest wall while the patient is under local anesthetic. It has one or more electrodes, which are placed in contact with the right atrium and/or right ventricular walls. If atrial fib develops, the atrial pacemaker is programmed to try and outrun the atrial fib initiating focus, and return the heart to sinus rhythm.
  
  
• A pacemaker is sometimes used in conjunction with radiofrequency ablation.
  
  
• Ventricular pacemaker is used when the atrial fib ventricular rate can not be controlled by medications, so the AV node is totally ablated, creating complete heart block. Now, the patient is pacemaker dependent, and the atrial fib is not corrected; it just can not communicate with the ventricles.
  
  
• Some machines and devices in your surroundings can interfere with the production of electrical impulses by your pacemaker. For example, airport security devices can deactivate pacemakers. Be sure you are familiar with which types of devices may have this effect, and avoid those devices.
  
  
• Wear an identification tag that shows that you have a pacemaker. You will need to present this identification when going through airport security and ask to be hand searched. Always tell any medical or dental personnel that you have a pacemaker.
  
  

|Surgery|

Before the development of catheter ablation, surgery was done to interrupt extra conducting pathways. Surgery was usually reserved for people whose arrhythmia did not respond to medication. Most of these people are now treated by catheter ablation.

A MAZE procedure may be performed. This procedure consists of a complicated series of incisions and sutures that are used to potentially cure or prevent atrial fib in patients having concomitant surgery for mitral valve problems or in younger patients having concomitant surgery for congenital heart defects (like Ebstein anomaly).

|Follow-up|

If you have no heart disease and medications succeed in controlling your heart rate, you can be sent home. You should follow up with your health care provider within 48 hours.

If your rhythm does not convert to normal by itself, you may need electrical cardioversion, or defibrillation.

• If you have been in atrial fibrillation longer than 48 hours, you will need 3 weeks of treatment with an anticoagulant medication, such as warfarin, before electric shock and for 3-4 weeks after.
  
  
• Anyone with underlying heart disease or those that do not respond to rate controlling treatment may require hospital care.

|Prevention|

If you do not have atrial fibrillation, you can lower your chance of getting this arrhythmia by reducing your risk factors for diseases associated with atrial fib. This includes risk factors for coronary heart disease and high blood pressure.

|Outlook|

The most dangerous complication of atrial fibrillation is stroke.

• The quivering of the atria prevents them from pumping effectively, and over time they tend to enlarge. This promotes formation of blood clots in the atria. If a piece of a clot breaks off and lodges in the brain, a stroke may result.
  
  
• Stroke occurs when part of the brain does not get enough blood to function properly.
  
  
• Much of the disability and some of the death associated with atrial fibrillation are caused by stroke.
  
  
• Someone with atrial fibrillation is about 3-5 times more likely to have a stroke than someone who does not have atrial fibrillation.
  
  
• The risk of stroke from atrial fibrillation for people aged 50-59 years is about 1.5%. For those aged 80-89 years, the risk is about 30%.

Another complication of atrial fibrillation is heart failure.

• In heart failure, the heart no longer contracts and pumps as strongly as it should.
  
  
• The very rapid contraction of the ventricles in atrial fibrillation can gradually weaken the muscle walls of the ventricles because of overwork and inadequate coronary blood flow.
  
  
• This is rare because most people seek treatment for atrial fibrillation before the heart begins to fail.
  
  
• Atrial fibrillation can worsen existing heart failure.
  
  

For most people with atrial fibrillation, relatively simple treatment dramatically lowers the risk of serious outcome. People with infrequent and brief episodes of atrial fibrillation may need no further treatment than learning to avoid the "triggers" of their episodes, such as caffeine, alcohol, or overeating.

|Support Groups and Counseling|

American Heart Association
National Center
7272 Greenville Avenue
Dallas, TX 75231
(800) 242-8721

North American Society of Pacing and Electrophysiology
Six Strathmore Road
Natick, MA 01760-2499
(508) 647-0100

|Web Links|

American College of Cardiology Foundation, Patient Education, Cardiac Arrhythmias 

American Heart Association

Heart Rhythm Society

atrial fibrillation, A fib, arrhythmia, atrial tachyarrhythmia, atrial tachycardia, holiday heart, heart rhythm disorders, atria, atrium, ventricles, AV node, atrioventricular node, sinoatrial node, SA node, sinus node, sinus rhythm, defibrillation, cardioversion, palpitations

Author: Noel G Boyle, MB, BCh, MD, PhD, Co-Director of Cardiac Electrophysiology, Assistant Professor, Department of Internal Medicine, Division of Cardiology, University of California at Los Angeles School of Medicine.

Coauthor(s): Paul Fleming, MD, Consulting Staff, Department of Emergency Medicine, Providence Saint Peter Hospital; Kathryn L Hale, MS, PA-C, Medical Writer, .com, Inc.

Editors: Alan D Forker, MD, Program Director of Cardiovascular Fellowship, Professor of Medicine, Department of Internal Medicine, University of Missouri at Kansas City School of Medicine; Mary L Windle, Pharm D, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Pharmacy Editor, .com, Inc; Anthony Anker, MD, FAAEM, Attending Physician, Emergency Department, Mary Washington Hospital, Fredericksburg, VA.