Atrial fibrillation (AF) is an arrhythmia of the heart. AF affects over 2 million Americans and accounts for one-third of all hospitalizations due to arrhythmias.1, Patients with AF often complain of ‘fluttering’ or palpitations in the chest, dizziness, fatigue and a ‘racing heart’. AF is caused when two of the heart’s chambers called the atria, do not  contract properly. When this happens the heart has trouble filling and expelling oxygen-rich blood with each beat. This can lead to blood pooling in the chambers of the heart. When blood pools, it can clot. Clots that form in the left atrium can be expelled into blood system to organs that receive blood from the heart. When clots travel to the brain, it can cause a stroke. Besides causing a stroke, AF can also cause a very fast heartbeat. This can be uncomfortable for the one who’s experiencing it and can lead to other problems like fainting and other more dangerous arrhythmias.
AF can be triggered by an underlying heart disease such as mitral valve prolapse, coronary artery disease, high blood pressure, or other conditions. This type of AF is usually chronic.

 
Many cases of AF are not connected with heart disease and may have a cause that is unknown. This type of AF is called Lone atrial fibrillation (LAF). An attack may last a few hours or several days, but rarely longer than a week. LAF is generally triggered by conditions such as low blood sugar, caffeine, alcohol or thyroid problems. LAF is not considered a chronic disease and is usually treatable by treating the underlying problem that is causing it.
The main goals when treating AF are to prevent stroke, control the heart rate and to treat symptoms. Preventing stroke is the most important goal in the treatment of AF. It comes as no surprise then that prevention of stroke is the focus of the new guidelines released for the treatment of AF. 

To prevent stroke in patients with AF, antithrombotic therapy is recommended. Antithrombotic therapy means using medications that decrease the blood’s ability to clot. This prevents clots from forming in the blood where they can travel to the brain and cause a stroke. Antithrombotic drugs used for this purpose include warfarin (Coumadin) and aspirin. Decisions about antithrombotic therapy are based on how many stroke risk factors a patient has.

Antithrombotic therapy recommendations are then made according to how many risk factors a patient has:

A Word About Warfarin

Warfarin is sometimes called a ‘blood thinner’. It works to prevent blood clots in the body. By preventing the formation of clots, it lessens the risk for stroke in many patients. Warfarin is a medication that needs to be closely monitored. Warfarin is dosed according to the results of a blood test called an INR. Measuring an INR while you are taking warfarin tells the doctor how fast your blood is clotting and if your dose of warfarin needs to be increased or decreased. The dose of warfarin is different for everyone. In other words, some people will only need 2 mg daily to get their INR in the right range. Others will need 10mg daily to get to their INR range.  In the beginning, your INR should be measured at least weekly until you are within the correct INR range. Then, your INR may be monitored less frequently.

Patients without mechanical heart valves who are taking warfarin will generally have an INR goal of 2 to 3. Patients with mechanical heart valves generally have an INR goal of 2.5-3.5. These goals may change, at your doctor’s discretion, based on your risk of stroke and your risk of bleeds. Patients taking warfarin may experience bruising. Bleeding while you are on warfarin can be a sign that your dose is too high and could lead to serious consequences. If you notice blood in your urine or excessive bleeding from your gums or other parts of the body, contact your doctor.
Warfarin also interacts with many other medications. it is important that your doctor and your pharmacy have a complete list of all of your current medications so that they can screen for drug interactions. Many over-the-counter herbals can interact with warfarin including coenzyme Q10, dong quai, garlic, ginkgo biloba ginseng and St. John’s Wort.

Antithrombotic Treatment in General

 It used to be that warfarin was used in most patients with AF to prevent stroke. But recent findings have found that although warfarin can prevent more strokes than aspirin in many patients, it also causes more bleeds. For this reason, the new guidelines recommend using aspirin for stroke prevention in certain AF patients. Aspirin is generally recommended only for low-risk patients. These are usually patients under the age of 65 with no risk factors. Some older patient may also be appropriate for aspirin therapy. These would be patients who are older but have not had a TIA, do not have high blood pressure, have not had a heart attack or angina, and do not have diabetes. It you fall into one of these categories, you should talk to your doctor about the pros and cons of using aspirin versus warfarin to prevent stroke.

Treatment with some kind of antithrombotic drug is recommended in all patients with AF unless they have LAF or antithrombotic treatment is contraindicated. For patients who are at low-risk or those who can not take warfarin, aspirin at 81 to 325mg daily may be used. For patients with AF who do not have a mechanical heart valve and have 1 or more certain risk factors, treatment with aspirin or warfarin may be considered. These risk factors include: age 65 to 74 years old, female gender, and history of coronary heart disease. 

Are You Protected?

Do you have AF? Are you at least taking aspirin to lessen your risk of stroke? Do you have any high risk factors or more than 1 moderate risk factor? If so, are you taking warfarin? If you find that your current medication regimen does not follow the guidelines we have just discussed, you should discuss it with your doctor. He/she may have a good reason why your therapy is not following the new recommendations. Perhaps you have other conditions that would prevent you from using warfarin, for example. Before starting aspirin on your own, be sure to talk to your doctor. Whatever the case, an open dialogue between you and your doctor is important in helping to ensure that you are getting the most of your medication regimen.

Author: Christi Larson, Pharm. D.

Dr. Larson is a Clinical Infusion Pharmacist, author of Empowered Medicine; A Guide for Consumers and creator of www.empoweredmedicine.com. You can read more about her by visiting www.EmpoweredMedicine.com and clicking on the 'About Us' tab.  EmpoweredMedicine.com is committed to providing evidence-based medical information.

REFERENCES
1. American College of Cardiology. ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation. Clinical Guidelines. http://www.acc.org (Accessed January 22, 2007)