|
Author: Morton F Arnsdorf, MD, MACC
Editors: Bradley P Knight, MD, FACC; Leah K Moynihan, RNC, MSN; Gordon M Saperia, MD, FACC
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 does not work correctly because of abnormal electrical activity. This means that only a small amount of blood is pumped out. The blood that remains in the atria becomes "sluggish" or static, which allows blood clots to form (see 'Risk of stroke' below.
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".)
* After heart surgery and, less often, after other types of surgery
* A variety of chronic lung diseases, particularly emphysema.
Atrial fibrillation can also be induced by external events. 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".)
* 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 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".)
Some people with atrial fibrillation have no apparent cause. When this occurs in people under age 60 to 65, it is called lone atrial fibrillation. The cause is not well understood, but the risk of blood clots is much lower in this group.
ATRIAL FIBRILLATION SYMPTOMS — Some people have no symptoms of AF while others have debilitating shortness of breath. 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
* Lightheadedness
* Mild shortness of breath and fatigue that limit the ability to exercise
As the ventricles beat more rapidly or irregularly, symptoms may be more severe and include:
* 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
* Fatigue
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. (See "Patient information: Stroke symptoms and diagnosis".)
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 and increases gradually to 5 percent each year for people 80 to 89 years.
Taking a blood thinner (usually warfarin [Coumadin®]) lowers the risk of stroke (see 'Treatment to prevent blood clots' below.
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, while lung function tests are sometimes used to look for 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".)
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 85 percent of preexisting blood clots in the left atrium to resolve.
Transesophageal echocardiogram — Use of procedure called transesophageal echocardiogram (TEE) is an alternative to delaying cardioversion while starting a blood thinner. TEE uses a small ultrasound device that is swallowed. The device allows the physician to see the left atria, looking for evidence of clots or slowed blood flow. If the atria appear to be without clots or slowed blood flow, cardioversion can be performed safely without warfarin pretreatment. Although there is still a risk that cardioversion may dislodge a clot that was not seen on the TEE, the risk is quite small.
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, most people treated with antiarrhythmic medications should continue blood thinners 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 ventricular rate 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.)
There are two major disadvantages with the rate control strategy: it is sometimes difficult to adequately control the rate and relieve symptoms; and chronic use of blood thinning medications carries a risk of bleeding.
A 2003 guideline from two major medical societies recommends rate control, along with a treatment to prevent blood clots, for the majority of patients. 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" and "Patient information: Implantable cardioverter-defibrillators".)
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".)
Increasingly, this therapy is being considered an initial option in young people who have symptoms of a-fib 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 maze procedure and the corridor operation, 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 warfarin (Coumadin®) and aspirin alone. Dabigatran and clopidogrel (Plavix®) may also be used.
Warfarin — Taking warfarin can reduce the risk of having a stroke by approximately 50 to 70 percent. (See "Patient information: Warfarin (Coumadin®)".)
The major problem with warfarin therapy 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.
Aspirin — Warfarin is the most effective treatment for preventing blood clots in patients at high-risk of stroke. However, treatment with aspirin is a reasonable option in certain people.
Reference:
http://www.uptodate.com/patients |
