ATRIAL FIBRILLATION OVERVIEW
Atrial fibrillation (also called AF or a-fib) is an abnormal rhythm of the heart. It is relatively common, affecting 2.3 million adults in the United States. Most people who develop atrial fibrillation are over 65 years of age. Atrial fibrillation is more frequent in men than women, and in whites than blacks.
There are two forms of this abnormal heart rhythm:
- Intermittent (paroxysmal) atrial fibrillation, which is characterized by episodes that occur with varying frequency and last for a variable period of time before spontaneously stopping.
- Chronic or persistent atrial fibrillation, which is sustained and does not usually stop spontaneously.
The purpose of this review is to describe the symptoms of atrial fibrillation, its risks, and to review current treatments.
WHAT IS ATRIAL FIBRILLATION?
In atrial fibrillation, part of the heart (the upper chambers, or atria) does not work correctly because of abnormal electrical activity. This means that blood is not forcefully moved out of these chambers. The blood that remains in the atria becomes "sluggish" or static, which allows blood clots to form (see 'Risk of stroke' below). Atrial fibrillation can be intermittent and stop on its own (paroxysmal), continue for several days and require treatment (persistent), or be present all the time (permanent).
ATRIAL FIBRILLATION CAUSES
Atrial fibrillation increases in frequency with aging and typically occurs in people who have underlying heart disease. Almost any heart disease can increase the risk of this abnormal rhythm, but the most common causes are:
- Hypertensive heart disease due to chronic high blood pressure.
- A heart attack (myocardial infarction, or MI)
- Heart failure
- Heart valve disease, such as mitral regurgitation or mitral stenosis. (See "Patient information: Mitral regurgitation (Beyond the Basics)".)
- After heart surgery and, less often, after other types of surgery
Atrial fibrillation can also be seen with other medical problems. These include:
- Alcohol and binge drinking — Binge drinkers can develop atrial fibrillation that is usually transient. This often occurs over weekends or holidays when alcohol intake is excessive. It is called "holiday heart syndrome."
- Hyperthyroidism — Atrial fibrillation occurs in about 13 percent of all people with an overactive thyroid gland (called hyperthyroidism). It has been estimated that hyperthyroidism accounts for 5 percent of cases of atrial fibrillation. Thus, blood testing for this disorder is recommended in anyone with AF since hyperthyroidism is treatable. (See "Patient information: Hyperthyroidism (overactive thyroid) (Beyond the Basics)".)
- Medications — Drugs that stimulate the heart can contribute to the development of atrial fibrillation. These include theophylline (used in the treatment of asthma or chronic lung disease) and caffeine.
- Sleep apnea — Atrial fibrillation can be caused by sleep apnea, a condition where patients stop breathing for prolonged periods of time while sleeping. Patients with atrial fibrillation who are overweight, or have a history of snoring or excessive sleepiness during the daytime, should be evaluated with a sleep study. Treatment for sleep apnea can eliminate atrial fibrillation in some patients. (See "Patient information: Sleep apnea in adults (Beyond the Basics)".)
- A variety of chronic lung diseases, particularly emphysema.
Some people with atrial fibrillation have no apparent cause. When this occurs in people under age 60 to risk of blood clots is much lower than it is in people who are older or who have known causes of atrial fibrillation.
ATRIAL FIBRILLATION SYMPTOMS
Some people have no symptoms at all while others have a variety of symptoms. Mild symptoms include:
- Unpleasant palpitations or irregularity of the heart beat
- Mild chest discomfort (sensation of tightness) or pain
- A sense of the heart racing
- Mild shortness of breath and fatigue that limit the ability to exercise
Some patients report severe symptoms:
- Difficulty breathing
- Shortness of breath with exertion
- Fainting, or near fainting, due to a reduction in blood flow to the brain
- Confusion, due to a reduction in blood supply to the brain
- Chest discomfort
Chest discomfort generally results from inadequate blood flow to meet the needs of the heart (called angina); this can be due to an increase in the heart's need for oxygen and/or a decrease in the heart's supply of blood and oxygen. In some cases, chest pain is due to the rapid heart rate itself or perhaps due to stretching of the heart's chambers. Chest discomfort can also result from worsening heart failure.
Risk of stroke — A serious complication associated with atrial fibrillation is stroke, which can lead to permanent brain damage. A stroke can occur if a blood clot forms in the left atrium because of sluggish blood flow and a piece of the clot (called an embolus) breaks off. The embolus enters the blood circulation and can block a small blood vessel. If this happens in the brain, a stroke can occur. The embolus may also travel to the eye, kidneys, spine, or important arteries of the arms or legs. When the symptoms of a stroke resolve completely within 24 hours, it is called a transient ischemic attack (TIA); many patients refer to this as a “mini-stroke.” (See "Patient information: Stroke symptoms and diagnosis (Beyond the Basics)".) Like atrial fibrillation, the risk of stroke increases with age. Without preventive treatment (eg, blood thinners), stroke occurs in approximately 1.3 percent of people with AF who are 50 to 59 years each year and increases gradually to 5 percent each year for people 80 to 89 years. The other risk factors for stroke include diabetes, high blood pressure, congestive heart failure, or prior stroke or embolus.
Taking a blood thinner lowers the risk of stroke (see 'Treatment to prevent blood clots' below). Blood thinners used in this setting include warfarin (Coumadin®), aspirin, or a new agent called dabigatran (Pradaxa®).
ATRIAL FIBRILLATION DIAGNOSIS
Atrial fibrillation is diagnosed with an electrocardiogram (ECG or EKG), which records the heart's electrical activity. Other tests, such as an echocardiogram (ultrasound), may be performed to look for heart failure or heart valve problems. Blood tests may be used to screen for thyroid disorders. Occasionally, sleep studies and lung function tests are sometimes used to look for sleep apnea or underlying lung disease.
ATRIAL FIBRILLATION TREATMENT
Electrical cardioversion — Electrical cardioversion involves the use of an electrical shock from a cardioverter, delivered by paddles placed on the chest, to "reset" the heart rhythm. Urgent cardioversion is usually performed if AF is interfering with heart's ability to supply blood and oxygen to vital organs. (See "Patient information: Cardioversion (Beyond the Basics)".)
Some people with newly diagnosed AF can undergo electrical or medical cardioversion (using an antiarrhythmic drug) immediately. However, due to the risk of stroke from blood clots lodged in the left atrium, many people are advised to delay cardioversion until starting treatment with a blood thinner. This medication, (usually warfarin [Coumadin®]) is given for three to four weeks, which allows most preexisting blood clots in the left atrium to resolve.
Transesophageal echocardiogram — Use of a procedure called transesophageal echocardiogram (TEE) is an alternative to delaying cardioversion while starting a blood thinner. The TEE avoids the need for delaying cardioversion until three to four weeks after starting warfarin, but it is still important that the blood is thinned at the time of the cardioversion. The blood can be thinned with either warfarin, or the blood thinner heparin that is administered subcutaneously (under the skin) or intravenously (by vein). A TEE uses a small ultrasound device that is swallowed. The device allows the physician to see the left atrium and look for evidence of blood clots. If there is no evidence of blood clot, cardioversion can be performed safely without three to four weeks of warfarin pretreatment. Although there is still a risk that cardioversion could result in a stroke even when a clot that is not seen on the TEE, the risk is quite small. Following cardioversion, a blood thinner must be continued for at least a month, assuming normal rhythm is maintained.
Long-term treatment — For people with intermittent or chronic atrial fibrillation, there are two long-term treatment options: rhythm control and rate control.
Rhythm control — Rhythm control refers to electrical or medical cardioversion followed by an antiarrhythmic drug to lower the risk of recurrent AF. After successful conversion to normal sinus rhythm, only 20 to 30 percent of people are in sinus rhythm after one year. This can be increased to between 40 and 80 percent by adding an antiarrhythmic drug.
The advantages to rhythm control include improved cardiac function and, for some people, reduced symptoms. Selected people who maintain a normal rhythm are allowed to stop blood thinning medications. However, rhythm control is more likely to reduce the frequency of AF than eliminate it entirely. Thus, many people treated with antiarrhythmic medications continue some form of blood thinning medications indefinitely.
The disadvantages of rhythm control are the high rate of recurrent AF and side effects associated with antiarrhythmic drugs, including the development of new abnormal heart rhythms.
Rate control — People who are treated with rate control continue to have AF. However, the person uses a medication (a beta blocker, a calcium channel blocker, or digoxin) to slow conduction through the AV node, thereby keeping the rate of the lower pumping chambers (ventricles) in the normal range. People who use this treatment require treatment with a blood thinner since there is a risk of blood clot formation and possible stroke. (See 'Treatment to prevent blood clots' below.)
The major disadvantage of the rate control strategy is sometimes it is difficult to adequately control the rate and relieve symptoms.
Either a rate control or a rhythm control strategy, along with a treatment to prevent blood clots, may be appropriate. You should discuss the risks and benefits of each type of treatment with your doctor or nurse.
Nonpharmacologic treatments — There are alternate ways to achieve rhythm or rate control, including radiofrequency catheter ablation, use of a pacemaker or implantable atrial defibrillator, and several surgical treatments. (See "Patient information: Pacemakers (Beyond the Basics)" and "Patient information: Implantable cardioverter-defibrillators (Beyond the Basics)".)
Radiofrequency ablation — Radiofrequency ablation is a procedure that can sometimes cure atrial fibrillation. The technique, however, is still evolving, and there is a small but real risk of serious complications, even with an experienced physician. (See "Patient information: Radiofrequency catheter ablation for the heart (Beyond the Basics)".)
Increasingly, this therapy is being considered an initial option in young people who have symptoms of AF who do not wish to take long-term medications. It is also being used increasingly in patients who are having recurrent atrial fibrillation despite using one or more antiarrhythmic drug. (See "Radiofrequency catheter ablation to prevent recurrent atrial fibrillation".)
Surgical procedures — Surgical procedures, including the complete maze procedure and the less invasive alternative surgeries, may be considered in some people with AF, especially those who must undergo open-heart surgery for other reasons. (See "Surgical approaches to prevent recurrent atrial fibrillation".)
TREATMENT TO PREVENT BLOOD CLOTS
People with atrial fibrillation have an increased risk of stroke as a result of blood clots that can form in the heart. As a result, most people are advised to use a treatment to reduce the risk of developing blood clots. The most commonly used treatments include anticoagulants (also called blood thinners) or antiplatelet drugs (such as aspirin).
Anticoagulant drugs — Taking an anticoagulant (blood thinner) can reduce the risk of having a stroke by approximately 50 to 70 percent. (See "Patient information: Warfarin (Coumadin) (Beyond the Basics)".)
Warfarin is an anticoagulant that has been used for many years, but a major problem with it is that it increases the risk of bleeding. The most serious type of bleeding is bleeding into the brain. However, the benefit of preventing strokes is greater than the small risk of bleeding into the brain in most cases. If you take warfarin, you will need careful monitoring with periodic blood tests to be sure you are taking the right dose of warfarin.
Dabigatran, apixaban, and rivaroxaban are newer anticoagulants that work as well as warfarin, and are as safe, but don’t require periodic blood tests. Patients should discuss with their doctors whether one of these newer agents is better for them than warfarin. Further information about dabigatran is available at the following website: http://circ.ahajournals.org/content/124/8/e209.full.
Antiplatelet drugs — Anticoagulants are the most effective treatment for preventing blood clots in patients at high-risk of stroke. However, treatment with antiplatelet drugs is a reasonable option in certain people. Aspirin is the most frequently used of this kind.
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Atrial fibrillation (The Basics)
Patient information: Implantable cardioverter-defibrillators (The Basics)
Patient information: Pacemakers (The Basics)
Patient information: Radiofrequency catheter ablation for the heart (The Basics)
Patient information: Wolff-Parkinson-White syndrome (The Basics)
Patient information: ECG and stress test (The Basics)
Patient information: Heart failure and atrial fibrillation (The Basics)
Patient information: Tachycardia (The Basics)
Patient information: Atrial flutter (The Basics)
Patient information: Mitral stenosis in adults (The Basics)
Patient information: Supraventricular tachycardia (SVT) (The Basics)
Patient information: Medicines for atrial fibrillation (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Mitral regurgitation (Beyond the Basics)
Patient information: Hyperthyroidism (overactive thyroid) (Beyond the Basics)
Patient information: Sleep apnea in adults (Beyond the Basics)
Patient information: Stroke symptoms and diagnosis (Beyond the Basics)
Patient information: Cardioversion (Beyond the Basics)
Patient information: Pacemakers (Beyond the Basics)
Patient information: Implantable cardioverter-defibrillators (Beyond the Basics)
Patient information: Radiofrequency catheter ablation for the heart (Beyond the Basics)
Patient information: Warfarin (Coumadin) (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Antiarrhythmic drugs to maintain sinus rhythm in patients with atrial fibrillation: Recommendations
Anticoagulation prior to and after restoration of sinus rhythm in atrial fibrillation
Antithrombotic therapy to prevent embolization in atrial fibrillation
Control of ventricular rate in atrial fibrillation: Nonpharmacologic therapy
Control of ventricular rate in atrial fibrillation: Pharmacologic therapy
Epidemiology of and risk factors for atrial fibrillation
General principles of the implantable cardioverter-defibrillator
Overview of atrial fibrillation
Paroxysmal atrial fibrillation
Radiofrequency catheter ablation to prevent recurrent atrial fibrillation
Restoration of sinus rhythm in atrial fibrillation
Rhythm control versus rate control in atrial fibrillation
Role of echocardiography in atrial fibrillation
Surgical approaches to prevent recurrent atrial fibrillation
The following organizations also provide reliable health information.
- National Library of Medicine
- National Heart, Lung, and Blood Institute
- American Heart Association