1. Atrial Fibrillation Slideshow Pictures
2. Take the Atrial Fibrillation Quiz!
3. Heart Disease Slideshow Pictures

Medical Author:

Daniel Lee Kulick, MD, FACC, FSCAI

Daniel Lee Kulick, MD, FACC, FSCAI

Dr. Kulick received his undergraduate and medical degrees from the University of Southern California, School of Medicine. He performed his residency in internal medicine at the Harbor-University of California Los Angeles Medical Center and a fellowship in the section of cardiology at the Los Angeles County-University of Southern California Medical Center. He is board certified in Internal Medicine and Cardiology.

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Medical Editor:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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In this Article

• Atrial fibrillation facts
• What is atrial fibrillation?
• What causes atrial fibrillation?
• What are the symptoms of atrial fibrillation?
• What are the complications of atrial fibrillation?
• What are the risk factors for developing atrial fibrillation?
• How is atrial fibrillation diagnosed?
• What is the treatment for atrial fibrillation?
• Reversing the risk factors that cause atrial fibrillation
• Slowing the heart rate with medications
• Anticoagulation to prevent blood clots and strokes
• Converting atrial fibrillation to a normal rhythm
• Procedures for treating and preventing atrial fibrillation
• What is new in atrial fibrillation?
• Atrial Fibrillation - Slideshow
• Take the Atrial Fibrillation Quiz!
• Heart Disease - Slideshow
• Atrial Fibrillation (A-Fib) FAQs
• Patient Comments: Atrial Fibrillation - Complications
• Patient Comments: Atrial Fibrillation - Medications
• Patient Comments: Atrial Fibrillation - Procedures
• Patient Comments: Atrial Fibrillation - Effective Treatments
• Patient Comments: Atrial Fibrillation - Symptoms and Signs
• Find a local Cardiologist in your town
• Atrial Fibrillation Index

Atrial fibrillation is one of the most important causes of stroke in the U.S. Warfarin (Coumadin) is a blood thinner that prevents the formation of blood clots. Studies in patients with chronic sustained atrial fibrillation and sporadic (paroxysmal) atrial fibrillation have shown that warfarin reduces strokes.

Aspirin is an antiplatelet agent. Platelets are elements in the blood that are necessary for blood clots to form. Aspirin can be considered a milder blood thinner than warfarin, but it is not as reliable as warfarin in preventing strokes in patients with atrial fibrillation. Some doctors prescribe aspirin to patients when the risk of bleeding from warfarin is believed to be too high and to patients who refuse to take warfarin. It must be remembered that antiplatelet agents such as aspirin and clopidogrel are NOT as effective as warfarin in preventing stroke.

Side effects of warfarin. There are some patients who are at increased risk for side effects from warfarin. Specifically:

• Patients with active stomach ulcers can develop ulcer bleeding while on warfarin.
• Elderly patients can experience hemorrhage into the brain while taking warfarin. The risk of hemorrhage is higher if the patient also has high blood pressure.
• Elderly patients who are unsteady and/or accident-prone are at an increased risk for trauma that can result in excessive bleeding.

Because of these serious side effects, patients using warfarin must be closely monitored with clotting tests such as the INR. The INR is a blood test that measures the degree of blood thinning. (The higher the value for the INR, the thinner the blood.) In preventing strokes in patients with atrial fibrillation, the dose of warfarin is adjusted to achieve a "therapeutic range" of INR. INR values higher than the therapeutic range are associated with an increased risk for bleeding, while values below the therapeutic range are associated with a diminished effectiveness in preventing stroke. Patients who are unreliable or unwilling to be monitored with regular measurements of INR may be considered for aspirin treatment rather than warfarin.

The beneficial effect of warfarin in preventing strokes needs to be balanced against the risk of excessive bleeding if the blood becomes too thin.

Candidates for warfarin. Doctors recommend warfarin to most elderly patients 65 years of age or older with paroxysmal (recurrent episodes) or chronic sustained atrial fibrillation. On balance, elderly patients with atrial fibrillation are more likely to benefit from warfarin because they are at a particularly high risk for stroke.

Patients younger than 65 with atrial fibrillation, especially those with prior embolic strokes, significant diseases of the heart, diabetes mellitus, high blood pressure, heart failure, coronary artery disease of the heart, or abnormally enlarged atrial chambers also are candidates for warfarin.

Patients who are not candidates for warfarin. Patients who are not candidates for warfarin include:

• patients with conditions that increase the risk of excessive bleeding, such as patients with active ulcers or other bleeding lesions in the intestines;
• elderly patients who are unsteady and/or accident-prone and who are at an increased risk for trauma that can result in excessive bleeding; and
• patients who are unreliable or unwilling to be monitored with regular INR measurements (for whom therapy with aspirin may be better).

There are newer agents that are as effective as warfarin in preventing strokes in patients with atrial fibrillation that do not require such intense monitoring or dietary restrictions. These agents (Xarelto and Pradaxa) are antithrombotic agents that work by a different mechanism from warfarin, and are suitable for many, but not all, patients. Indications should be discussed with the patient's physician.