Sunday, February 11, 2007
AF en apnea
* 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.
Some patients with atrial fibrillation have no apparent cause. When this occurs in patients 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 these patients.
DIAGNOSIS — Atrial fibrillation is diagnosed by obtaining an electrocardiogram (ECG or EKG), which records the heart's electrical activity. Other tests are performed to establish a cause for the atrial fibrillation, including measuring blood pressure to evaluate for hypertension and measuring thyroid stimulating hormone (TSH) in order to rule out an overactive thyroid gland. Other tests, such as an echocardiogram (ultrasound), may be performed to look for other causes of atrial fibrillation such as heart failure or heart valve problems, while lung function tests are sometimes used to look for underlying lung disease.
Patients who have symptoms suggesting atrial fibrillation, but who cannot be diagnosed with AF or other rhythm disorders based upon an office electrocardiogram, may need further monitoring. Continuous monitoring (eg, Holter monitor, show figure 3) or a recording device (eg, event monitor, show figure 4) that can be turned on by the patient when they feel palpitations are often used
SYMPTOMS AND RISKS— Three main factors determine the symptoms and risks of atrial fibrillation: how fast the ventricles are beating; the presence or absence of underlying heart disease; and the formation of blood clots, particularly in the left atrium, that can break off and enter the systemic circulation, possibly leading to a stroke or blockage of arteries going to other important organs.
Symptoms — Patient awareness of atrial fibrillation is highly variable; some patients have no symptoms while others may have debilitating shortness of breath. Most patients who are well controlled on medical therapy have no or mild symptoms; more severe symptoms occur when the ventricular rate is not well controlled. 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 to stretching of the heart's chambers.
If the heart rate is very rapid, or if the patient has underlying heart disease, more serious symptoms of heart failure can develop:
* Shortness of breath at rest or at night
* Swelling of the legs
* Rapid weight gain due to fluid accumulation
* Angina or even a heart attack, primarily in patients with underlying coronary disease
Worsening heart failure or the development of angina may also produce other types of serious and potentially life-threatening arrhythmias.
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 (also called an embolus) breaks off. The embolus enters the blood circulation and can obstruct a small blood vessel. The most dangerous place for this to occur is the brain, resulting in a stroke, but the embolus may also go to the eye, kidneys, spine, or important arteries of the arms or legs.
Like atrial fibrillation, the risk of stroke increases with age. Without preventive treatment (eg, blood thinners), stroke occurs in approximately 1.3 percent of patients aged 50 to 59 years and increases gradually to 5.1 percent each year for those aged 80 to 89 years. These percentages are average rates; for each patient the risk is also influenced by a number of other factors, including the presence of hypertension and additional heart disease. In some patients with multiple underlying medical conditions, the annual risk of a stroke can be as high as 8 to 10 percent.
The administration of a blood thinner (usually warfarin [Coumadin®]) lowers the risk of stroke by 50 to 65 percent in intermediate to high risk patients. Warfarin therapy is typically referred to as anticoagulation (see "Warfarin therapy" below). In patients at intermediate to high risk for stroke, no other therapy lowers the risk of a stroke as much as warfarin.
Low-risk patients have a stroke rate of less than 1 percent per year (usually patients under 60 to 65 years of age with one or no additional risk factors). Patients with this low-risk profile may be treated with aspirin instead of warfarin.
TREATMENT — There are four main issues that must be addressed in the treatment of atrial fibrillation: the need for hospitalization; conversion to and maintenance of normal sinus rhythm; rhythm versus rate control; and prevention of embolus formation and stroke.
Hospitalization — Most patients who have atrial fibrillation do not need to be admitted to the hospital. Situations in which hospitalization might be indicated include:
* Symptoms of chest pain or pressure associated with electrocardiogram (ECG) changes that suggest the person is having a heart attack or angina due to a reduction in blood supply to the heart.
* Patients who have other serious complications of atrial fibrillation, including low blood pressure, trouble breathing, heart failure, or stroke.
* An underlying medical condition that caused the atrial fibrillation and that needs treatment itself.
* When patients are cardioverted from atrial fibrillation to a normal sinus rhythm.
* Patients who may be safer in a hospital while medications are started.
* Patients who are at a particularly high risk of developing a thrombus in the atrium or who should be observed for potential bleeding problems while anticoagulation is started.
Conversion to normal rhythm — Patients with paroxysmal (intermittent) atrial fibrillation have episodes of varying duration that resolve spontaneously. Careful monitoring has shown that up to 90 percent of recurrent episodes are not recognized by the patient, including some that last more than two days.
Spontaneous conversion to normal sinus rhythm is much less likely in patients with chronic (persistent) atrial fibrillation. In these patients, atrial fibrillation is converted to sinus rhythm using either electrical cardioversion or medications.
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 recommended if atrial fibrillation is interfering with heart's ability to supply blood and oxygen to vital organs. Signs of this include a fall in blood pressure, angina (chest pain), shortness of breath, and/or heart failure.
Some patients with newly diagnosed atrial fibrillation can undergo electrical or medical cardioversion (using an antiarrhythmic drug) immediately. However, due to the risk of stroke from left atrial blood clots, doctors frequently recommend waiting to cardiovert until the patient has been treated 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.
Even though normal electrical activity is restored with the cardioversion, the atria may not resume normal muscle contraction for several days or weeks. Thus, there is still a risk of clot formation in the period immediately after cardioversion. For this reason, a blood thinner is recommended for at least four weeks after cardioversion.
Repeat cardioversion is a reasonable treatment for patients with atrial fibrillation that has recurred after a long duration of normal heart rhythm; it is most likely to be successful in younger patients with a short history of atrial fibrillation.
Transesophageal echocardiogram — An alternative to waiting involves a procedure called transesophageal echocardiogram (TEE). TEE uses a small ultrasound device that is swallowed to visualize 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.
Other treatment options — For patients with intermittent or chronic atrial fibrillation, there are two long-term treatment options: rhythm control and rate control. Two large clinical trials have addressed the effectiveness and safety of these two approaches. Before discussing these trials, it is useful to review the meaning of rhythm control and rate control and both the benefits and risks of long-term warfarin therapy.
Rhythm control — Rhythm control refers to electrical or medical cardioversion followed by an antiarrhythmic drug to lower the risk of recurrence of atrial fibrillation. After successful conversion to normal sinus rhythm, only 20 to 30 percent of patients 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 are improved cardiac function and, for some patients, reduced symptoms. Selected patients who are effectively maintained in normal rhythm may be allowed to stop chronic anticoagulation. However, rhythm control is more likely to reduce the frequency of AF than eliminate it entirely. Thus most patients treated with antiarrhythmic medications should continue anticoagulation therapy indefinitely.
The disadvantages of rhythm control are the high rate of recurrent atrial fibrillation and side effects associated with antiarrhythmic drugs, including the development of new abnormal heart rhythms.
Rate control — In patients who are treated with rate control, atrial fibrillation is allowed to continue; the patient uses a medication (a beta blocker, a calcium channel blocker, or digoxin) to slow conduction through the AV node, thereby slowing the ventricular rate into the normal range. All patients require chronic therapy with a blood thinner since there is a continued risk of blood clot formation and possible stroke.
There are two major disadvantages with the rate control strategy: it is sometimes difficult to adequately control the rate and relieve symptoms; and chronic anticoagulation, which carries a risk of bleeding, is mandatory, .
Nonpharmacologic treatments — There are alternatives to medicines to achieve rhythm or rate control. Nonpharmacologic treatments include radiofrequency catheter ablation, use of a pacemaker or implantable atrial defibrillator, and several surgical treatments. Radiofrequency ablation can result in a cure when performed by an experienced physician in carefully selected patients. (See "Patient information: Radiofrequency catheter ablation" and see "Patient information: Pacemakers" and see "Patient information: Implantable cardioverter-defibrillators").
Surgical procedures, including the maze procedure and the corridor operation, may be considered in some patients with atrial fibrillation, especially those who must undergo open-heart surgery for other reasons.
Warfarin therapy — Chronic warfarin therapy reduces the rate of stroke by approximately 50 to 70 percent in patients with atrial fibrillation who are at intermediate to high risk. The potential benefit is actually greater since as many as one-half of strokes in treated patients are due to a less than optimal degree of blood thinning. (See "Patient information: Warfarin (Coumadin®)").
The major problem with warfarin therapy is that anticoagulation can lead to bleeding. In a large review of studies of patients with atrial fibrillation, the incidence of major bleeding events with warfarin was increased by 0.9 percent per year compared to aspirin (2.2 versus 1.3 percent per year). The major concern is bleeding into the brain.
The major risk factors for bleeding into the brain are:
* Age greater than 70 years
* Uncontrolled high blood pressure
* History of prior stroke
* Excessive anticoagulation.
However, the risk of bleeding into the brain is substantially smaller than the benefit of preventing strokes in patients who use warfarin.
Patients taking warfarin must be carefully and continuously monitored with periodic blood tests to make certain that the degree of blood thinning is sufficient to protect against stroke but not too great to promote bleeding.
Clinical trials — In the past, most physicians preferred rhythm control because of the presumed advantages of better heart function and a much lower risk of stroke in patients in normal sinus rhythm. However, two major trials directly compared rhythm control and rate control. There were two major conclusions:
* The outcomes were generally similar, but both studies showed a trend toward a better outcome with rate control compared to rhythm control (show figure 4 and show figure 5).
* Contrary to expectations, rhythm control was associated with a trend toward a higher risk of stroke compared to rate control. However, the majority of strokes occurred in patients receiving no or suboptimal warfarin therapy. This finding suggests that patients treated with rhythm control should usually continue anticoagulation. In other words, choosing rhythm control should be based upon the desire to improve symptoms, not an effort to avoid chronic anticoagulation.
Patients should talk to their healthcare provider about which approach is best. A 2003 guideline from two major medical societies recommends rate control with chronic anticoagulation for the majority of patients. The type of blood thinner therapy (warfarin or aspirin) recommended depends upon a patient's risk of stroke, which can be determined with a healthcare provider.
Newer therapies — There are limitations to current medical therapy of atrial fibrillation: normal sinus rhythm cannot be maintained in most patients with antiarrhythmic drugs, which also have side effects; rate control that control symptoms cannot be attained in all patients; and all patients except those at low risk require chronic warfarin therapy, which has a risk of bleeding.
Surgery and radiofrequency catheter ablation have been used for rate control and cure of atrial fibrillation. Patients with symptomatic atrial fibrillation that cannot be adequately controlled with medicines may be candidates for catheter ablation to cure the atrial fibrillation.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information. Some of the most pertinent include:
Professional Level Information:
Causes of atrial fibrillation
Overview of the presentation and management of atrial fibrillation
Paroxysmal atrial fibrillation
Anticoagulation to prevent embolization in atrial fibrillation
Control of ventricular rate in atrial fibrillation: Nonpharmacologic therapy
Control of ventricular rate in atrial fibrillation: Pharmacologic therapy
Restoration of sinus rhythm in atrial fibrillation: Recommendations
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.
* National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
* National Heart, Lung, and Blood Institute
(www.nhlbi.nih.gov/)
* American Heart Association
(www.americanheart.org)
* Harvard Center for Cancer Prevention
(www.yourdiseaserisk.harvard.edu/)
Includes a calculator for estimating the risk of stroke
* Atrial Fibrillation Foundation
(www.affacts.org)
* Heart Rhythm Society
(www.hrsonline.org)
[1-12]
Use of UpToDate is subject to the Subscription and License Agreement.
REFERENCES
1. Benjamin, EJ, Wolf, PA, D'Agostino, RB, et al. Impact of atrial fibrillation on the risk of death: The Framingham Heart Study. Circulation 1998; 98:946.
2. Danias, PG, Caulfield, TA, Weigner, MJ, et. al. Likelihood of spontaneous conversion of atrial fibrillation to sinus rhythm. J Am Coll Cardiol 1998; 31:588.
3. Page, RL, Wilkinson, WE, Clair, WK, et al. Asymptomatic arrhythmias in patients with symptomatic paroxysmal atrial fibrillation and paroxysmal supraventricular tachycardia. Circulation 1994; 89:224.
4. Silverman, DI, Manning, WJ. Strategies for cardioversion of atrial fibrillation--time for a change?. N Engl J Med 2001; 344:1468.
5. Weigner, MJ, Caulfield, TA, Danias, PG, et al. Risk for clinical thromboembolism associated with conversion to sinus rhythm in patients with atrial fibrillation lasting less than 48 hours. Ann Intern Med 1997; 126:615.
6. Go, AS, Hylek, EM, Chang, Y, et al. Anticoagulation therapy for stroke prevention in atrial fibrillation: how well do randomized trials translate into clinical practice?. JAMA 2003; 290:2685.
7. Van Walraven, C, Hart, RG, Singer, DE, et al. Oral anticoagulants vs aspirin in nonvalvular atrial fibrillation: An Individual patient meta-analysis. JAMA 2002; 288:2441.
8. Klein, AL, Grimm, RA, Murray, D, et al, for the Assessment of Cardioversion Using Transesophageal Echocardiography Investigators. Use of transesophageal echocardiography to guide cardioversion in patients with atrial fibrillation. N Engl J Med 2001; 344:1411.
9. Roy, D, Talajic, M, Dorian, P, et al. Amiodarone to prevent recurrence of atrial fibrillation. Canadian Trial of Atrial Fibrillation Investigators. N Engl J Med 2000; 342:913.
10. Wyse, DG, Waldo, AL, DiMarco, JP, et al. A comparison of rate control and rhythm control in patients with atrial fibrillation. The atrial fibrillation follow-up investigation of rhythm management (AFFIRM) investigators. N Engl J Med 2002; 347:1825.
11. Van Gelder, IC, Hagens, VE, Bosker, HA, et al. A comparison of rate control and rhythm control in patients with recurrent persistent atrial fibrillation. N Engl J Med 2002; 347:1834.
12. Snow, V, Weiss, KB, LeFevre, M, et al. Management of newly detected atrial fibrillation: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians. Ann Intern Med 2003; 139:1009.
Some patients with atrial fibrillation have no apparent cause. When this occurs in patients 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 these patients.
DIAGNOSIS — Atrial fibrillation is diagnosed by obtaining an electrocardiogram (ECG or EKG), which records the heart's electrical activity. Other tests are performed to establish a cause for the atrial fibrillation, including measuring blood pressure to evaluate for hypertension and measuring thyroid stimulating hormone (TSH) in order to rule out an overactive thyroid gland. Other tests, such as an echocardiogram (ultrasound), may be performed to look for other causes of atrial fibrillation such as heart failure or heart valve problems, while lung function tests are sometimes used to look for underlying lung disease.
Patients who have symptoms suggesting atrial fibrillation, but who cannot be diagnosed with AF or other rhythm disorders based upon an office electrocardiogram, may need further monitoring. Continuous monitoring (eg, Holter monitor, show figure 3) or a recording device (eg, event monitor, show figure 4) that can be turned on by the patient when they feel palpitations are often used
SYMPTOMS AND RISKS— Three main factors determine the symptoms and risks of atrial fibrillation: how fast the ventricles are beating; the presence or absence of underlying heart disease; and the formation of blood clots, particularly in the left atrium, that can break off and enter the systemic circulation, possibly leading to a stroke or blockage of arteries going to other important organs.
Symptoms — Patient awareness of atrial fibrillation is highly variable; some patients have no symptoms while others may have debilitating shortness of breath. Most patients who are well controlled on medical therapy have no or mild symptoms; more severe symptoms occur when the ventricular rate is not well controlled. 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 to stretching of the heart's chambers.
If the heart rate is very rapid, or if the patient has underlying heart disease, more serious symptoms of heart failure can develop:
* Shortness of breath at rest or at night
* Swelling of the legs
* Rapid weight gain due to fluid accumulation
* Angina or even a heart attack, primarily in patients with underlying coronary disease
Worsening heart failure or the development of angina may also produce other types of serious and potentially life-threatening arrhythmias.
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 (also called an embolus) breaks off. The embolus enters the blood circulation and can obstruct a small blood vessel. The most dangerous place for this to occur is the brain, resulting in a stroke, but the embolus may also go to the eye, kidneys, spine, or important arteries of the arms or legs.
Like atrial fibrillation, the risk of stroke increases with age. Without preventive treatment (eg, blood thinners), stroke occurs in approximately 1.3 percent of patients aged 50 to 59 years and increases gradually to 5.1 percent each year for those aged 80 to 89 years. These percentages are average rates; for each patient the risk is also influenced by a number of other factors, including the presence of hypertension and additional heart disease. In some patients with multiple underlying medical conditions, the annual risk of a stroke can be as high as 8 to 10 percent.
The administration of a blood thinner (usually warfarin [Coumadin®]) lowers the risk of stroke by 50 to 65 percent in intermediate to high risk patients. Warfarin therapy is typically referred to as anticoagulation (see "Warfarin therapy" below). In patients at intermediate to high risk for stroke, no other therapy lowers the risk of a stroke as much as warfarin.
Low-risk patients have a stroke rate of less than 1 percent per year (usually patients under 60 to 65 years of age with one or no additional risk factors). Patients with this low-risk profile may be treated with aspirin instead of warfarin.
TREATMENT — There are four main issues that must be addressed in the treatment of atrial fibrillation: the need for hospitalization; conversion to and maintenance of normal sinus rhythm; rhythm versus rate control; and prevention of embolus formation and stroke.
Hospitalization — Most patients who have atrial fibrillation do not need to be admitted to the hospital. Situations in which hospitalization might be indicated include:
* Symptoms of chest pain or pressure associated with electrocardiogram (ECG) changes that suggest the person is having a heart attack or angina due to a reduction in blood supply to the heart.
* Patients who have other serious complications of atrial fibrillation, including low blood pressure, trouble breathing, heart failure, or stroke.
* An underlying medical condition that caused the atrial fibrillation and that needs treatment itself.
* When patients are cardioverted from atrial fibrillation to a normal sinus rhythm.
* Patients who may be safer in a hospital while medications are started.
* Patients who are at a particularly high risk of developing a thrombus in the atrium or who should be observed for potential bleeding problems while anticoagulation is started.
Conversion to normal rhythm — Patients with paroxysmal (intermittent) atrial fibrillation have episodes of varying duration that resolve spontaneously. Careful monitoring has shown that up to 90 percent of recurrent episodes are not recognized by the patient, including some that last more than two days.
Spontaneous conversion to normal sinus rhythm is much less likely in patients with chronic (persistent) atrial fibrillation. In these patients, atrial fibrillation is converted to sinus rhythm using either electrical cardioversion or medications.
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 recommended if atrial fibrillation is interfering with heart's ability to supply blood and oxygen to vital organs. Signs of this include a fall in blood pressure, angina (chest pain), shortness of breath, and/or heart failure.
Some patients with newly diagnosed atrial fibrillation can undergo electrical or medical cardioversion (using an antiarrhythmic drug) immediately. However, due to the risk of stroke from left atrial blood clots, doctors frequently recommend waiting to cardiovert until the patient has been treated 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.
Even though normal electrical activity is restored with the cardioversion, the atria may not resume normal muscle contraction for several days or weeks. Thus, there is still a risk of clot formation in the period immediately after cardioversion. For this reason, a blood thinner is recommended for at least four weeks after cardioversion.
Repeat cardioversion is a reasonable treatment for patients with atrial fibrillation that has recurred after a long duration of normal heart rhythm; it is most likely to be successful in younger patients with a short history of atrial fibrillation.
Transesophageal echocardiogram — An alternative to waiting involves a procedure called transesophageal echocardiogram (TEE). TEE uses a small ultrasound device that is swallowed to visualize 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.
Other treatment options — For patients with intermittent or chronic atrial fibrillation, there are two long-term treatment options: rhythm control and rate control. Two large clinical trials have addressed the effectiveness and safety of these two approaches. Before discussing these trials, it is useful to review the meaning of rhythm control and rate control and both the benefits and risks of long-term warfarin therapy.
Rhythm control — Rhythm control refers to electrical or medical cardioversion followed by an antiarrhythmic drug to lower the risk of recurrence of atrial fibrillation. After successful conversion to normal sinus rhythm, only 20 to 30 percent of patients 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 are improved cardiac function and, for some patients, reduced symptoms. Selected patients who are effectively maintained in normal rhythm may be allowed to stop chronic anticoagulation. However, rhythm control is more likely to reduce the frequency of AF than eliminate it entirely. Thus most patients treated with antiarrhythmic medications should continue anticoagulation therapy indefinitely.
The disadvantages of rhythm control are the high rate of recurrent atrial fibrillation and side effects associated with antiarrhythmic drugs, including the development of new abnormal heart rhythms.
Rate control — In patients who are treated with rate control, atrial fibrillation is allowed to continue; the patient uses a medication (a beta blocker, a calcium channel blocker, or digoxin) to slow conduction through the AV node, thereby slowing the ventricular rate into the normal range. All patients require chronic therapy with a blood thinner since there is a continued risk of blood clot formation and possible stroke.
There are two major disadvantages with the rate control strategy: it is sometimes difficult to adequately control the rate and relieve symptoms; and chronic anticoagulation, which carries a risk of bleeding, is mandatory, .
Nonpharmacologic treatments — There are alternatives to medicines to achieve rhythm or rate control. Nonpharmacologic treatments include radiofrequency catheter ablation, use of a pacemaker or implantable atrial defibrillator, and several surgical treatments. Radiofrequency ablation can result in a cure when performed by an experienced physician in carefully selected patients. (See "Patient information: Radiofrequency catheter ablation" and see "Patient information: Pacemakers" and see "Patient information: Implantable cardioverter-defibrillators").
Surgical procedures, including the maze procedure and the corridor operation, may be considered in some patients with atrial fibrillation, especially those who must undergo open-heart surgery for other reasons.
Warfarin therapy — Chronic warfarin therapy reduces the rate of stroke by approximately 50 to 70 percent in patients with atrial fibrillation who are at intermediate to high risk. The potential benefit is actually greater since as many as one-half of strokes in treated patients are due to a less than optimal degree of blood thinning. (See "Patient information: Warfarin (Coumadin®)").
The major problem with warfarin therapy is that anticoagulation can lead to bleeding. In a large review of studies of patients with atrial fibrillation, the incidence of major bleeding events with warfarin was increased by 0.9 percent per year compared to aspirin (2.2 versus 1.3 percent per year). The major concern is bleeding into the brain.
The major risk factors for bleeding into the brain are:
* Age greater than 70 years
* Uncontrolled high blood pressure
* History of prior stroke
* Excessive anticoagulation.
However, the risk of bleeding into the brain is substantially smaller than the benefit of preventing strokes in patients who use warfarin.
Patients taking warfarin must be carefully and continuously monitored with periodic blood tests to make certain that the degree of blood thinning is sufficient to protect against stroke but not too great to promote bleeding.
Clinical trials — In the past, most physicians preferred rhythm control because of the presumed advantages of better heart function and a much lower risk of stroke in patients in normal sinus rhythm. However, two major trials directly compared rhythm control and rate control. There were two major conclusions:
* The outcomes were generally similar, but both studies showed a trend toward a better outcome with rate control compared to rhythm control (show figure 4 and show figure 5).
* Contrary to expectations, rhythm control was associated with a trend toward a higher risk of stroke compared to rate control. However, the majority of strokes occurred in patients receiving no or suboptimal warfarin therapy. This finding suggests that patients treated with rhythm control should usually continue anticoagulation. In other words, choosing rhythm control should be based upon the desire to improve symptoms, not an effort to avoid chronic anticoagulation.
Patients should talk to their healthcare provider about which approach is best. A 2003 guideline from two major medical societies recommends rate control with chronic anticoagulation for the majority of patients. The type of blood thinner therapy (warfarin or aspirin) recommended depends upon a patient's risk of stroke, which can be determined with a healthcare provider.
Newer therapies — There are limitations to current medical therapy of atrial fibrillation: normal sinus rhythm cannot be maintained in most patients with antiarrhythmic drugs, which also have side effects; rate control that control symptoms cannot be attained in all patients; and all patients except those at low risk require chronic warfarin therapy, which has a risk of bleeding.
Surgery and radiofrequency catheter ablation have been used for rate control and cure of atrial fibrillation. Patients with symptomatic atrial fibrillation that cannot be adequately controlled with medicines may be candidates for catheter ablation to cure the atrial fibrillation.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information. Some of the most pertinent include:
Professional Level Information:
Causes of atrial fibrillation
Overview of the presentation and management of atrial fibrillation
Paroxysmal atrial fibrillation
Anticoagulation to prevent embolization in atrial fibrillation
Control of ventricular rate in atrial fibrillation: Nonpharmacologic therapy
Control of ventricular rate in atrial fibrillation: Pharmacologic therapy
Restoration of sinus rhythm in atrial fibrillation: Recommendations
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.
* National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
* National Heart, Lung, and Blood Institute
(www.nhlbi.nih.gov/)
* American Heart Association
(www.americanheart.org)
* Harvard Center for Cancer Prevention
(www.yourdiseaserisk.harvard.edu/)
Includes a calculator for estimating the risk of stroke
* Atrial Fibrillation Foundation
(www.affacts.org)
* Heart Rhythm Society
(www.hrsonline.org)
[1-12]
Use of UpToDate is subject to the Subscription and License Agreement.
REFERENCES
1. Benjamin, EJ, Wolf, PA, D'Agostino, RB, et al. Impact of atrial fibrillation on the risk of death: The Framingham Heart Study. Circulation 1998; 98:946.
2. Danias, PG, Caulfield, TA, Weigner, MJ, et. al. Likelihood of spontaneous conversion of atrial fibrillation to sinus rhythm. J Am Coll Cardiol 1998; 31:588.
3. Page, RL, Wilkinson, WE, Clair, WK, et al. Asymptomatic arrhythmias in patients with symptomatic paroxysmal atrial fibrillation and paroxysmal supraventricular tachycardia. Circulation 1994; 89:224.
4. Silverman, DI, Manning, WJ. Strategies for cardioversion of atrial fibrillation--time for a change?. N Engl J Med 2001; 344:1468.
5. Weigner, MJ, Caulfield, TA, Danias, PG, et al. Risk for clinical thromboembolism associated with conversion to sinus rhythm in patients with atrial fibrillation lasting less than 48 hours. Ann Intern Med 1997; 126:615.
6. Go, AS, Hylek, EM, Chang, Y, et al. Anticoagulation therapy for stroke prevention in atrial fibrillation: how well do randomized trials translate into clinical practice?. JAMA 2003; 290:2685.
7. Van Walraven, C, Hart, RG, Singer, DE, et al. Oral anticoagulants vs aspirin in nonvalvular atrial fibrillation: An Individual patient meta-analysis. JAMA 2002; 288:2441.
8. Klein, AL, Grimm, RA, Murray, D, et al, for the Assessment of Cardioversion Using Transesophageal Echocardiography Investigators. Use of transesophageal echocardiography to guide cardioversion in patients with atrial fibrillation. N Engl J Med 2001; 344:1411.
9. Roy, D, Talajic, M, Dorian, P, et al. Amiodarone to prevent recurrence of atrial fibrillation. Canadian Trial of Atrial Fibrillation Investigators. N Engl J Med 2000; 342:913.
10. Wyse, DG, Waldo, AL, DiMarco, JP, et al. A comparison of rate control and rhythm control in patients with atrial fibrillation. The atrial fibrillation follow-up investigation of rhythm management (AFFIRM) investigators. N Engl J Med 2002; 347:1825.
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# posted by roodbont @ 3:43 PM 
