What is atrial fibrillation?

Atrial fibrillation is a heart rhythm disturbance. It causes a fast and irregular heartbeat. It occurs when the smaller, upper chambers of the heart contract in a very rapid, uncoordinated manner. These upper chambers of the heart are called the right and left atria.

Fibrillation interferes with the heart's usual steady, efficient pumping. Because the heart cannot pump the blood as well, your blood pressure may drop. Your blood then may not be able to deliver enough oxygen to the tissues of your body, including the heart itself.

How does it occur?

A natural electrical impulse causes your heart to go through its pumping motion. Normally this impulse for each heartbeat begins in the atria of the heart. It then moves along a specific pathway to the lower chambers of the heart (the ventricles).

In atrial fibrillation the usual sequence of events is interrupted. The normal coordinated contraction (squeezing) of atria and ventricles does not occur. The atrial muscles quiver and do not coordinate with the ventricular contractions. This loss of coordination causes each contraction of the heart to lose power. It also causes loss of the normal control of your heart rate.

Two common causes of atrial fibrillation are:

• heart disease, such as coronary heart disease or heart failure due to many years of high blood pressure

• mitral valve prolapse, a malfunction of the valve between the left atrium and left ventricle.

Other causes of atrial fibrillation include:

• hyperthyroidism

• pneumonia

• chronic lung disease

• heavy drinking of alcohol

• electrolyte (mineral) imbalances

• medications, such as theophylline.

Sometimes no cause for the fibrillation can be found.

What are the symptoms?

The most common symptoms are:

• irregular heart rate

• fast heart rate

• weakness

• fatigue

• lightheadedness

• shortness of breath.

Some people have chest pain. If your heart is pumping very poorly, your blood pressure may drop severely and you may faint.

Occasionally, the first symptom is a stroke, caused by a blood clot that formed in the fibrillating atrium and traveled to the brain.

Some people have no symptoms.

How is it diagnosed?

Your health care provider will ask about your symptoms and examine you. The diagnosis can be confirmed with an electrocardiogram (ECG). An ECG measures the electrical activity of your heart. It will show a special pattern for atrial fibrillation. Your provider will use your medical history, physical exam, and blood tests to look for a treatable cause of the abnormal heartbeat.

A helpful additional test is an echocardiogram. This test uses sound waves to show images of your heart on a computer. It is a way to check for structural problems, such as an abnormal mitral valve, which might be causing fibrillations.

How is it treated?

Initial treatment depends on:

• the severity of your symptoms

• the apparent cause of the fibrillation

• your history of heart problems or stroke.

If the fibrillation is new and is causing severe symptoms, you may be treated with cardioversion (electrical shock). The electrical shock causes your heart to begin beating normally again.

If your symptoms are mild, at first you may be given intravenous medication (through a vein). Then you may take oral medication over the course of hours to days. If the medication does not convert the heart to normal rhythm, your health care provider may try electrical cardioversion (while you are sedated). Often this is successful.

If a treatable underlying cause for your fibrillation is found, usually treatment of the problem will make the fibrillation stop. Otherwise, long-term use of medication prescribed by your health care provider may be necessary to control your heart rate. You should avoid stimulants such as caffeine and alcohol.

What are the complications?

The most serious complication of atrial fibrillation is a stroke caused by a blood clot in the brain. When the flow of blood slows down in the fibrillating atrium, the blood may begin to clot. Clots may then travel in the bloodstream to the brain, where they can block blood flow to a part of the brain and cause a stroke.

If you continue to have atrial fibrillation despite treatment, you have a greater risk of stroke. This is especially true if you have other heart disease or an artificial heart valve. In this case you may need to take an anticoagulant (blood thinner) to reduce the risk of clot formation and stroke. If you are less than 60 years old and do not have other heart disease or an artificial valve, your risk for stroke is lower and you may not need to take a blood thinner.

If your atrial fibrillation continues, you are also at risk for fainting or falling and breaking a bone. This is especially true for elderly women.

How do I care for someone with atrial fibrillation?

Two important aspects of caring for someone with atrial fibrillation are:

• Make sure he or she takes the prescribed medications properly.

• See that he or she gets follow-up blood tests to check on the level of anticoagulant in the blood.

Report promptly to the health care provider any recurring or new symptoms, such as episodes of falling or fainting. In certain situations a pacemaker may be recommended to try to control these symptoms.

How do I prevent atrial fibrillation?

Having a lifestyle and diet that is healthy for your heart may help stop atrial fibrillation from developing.