Atrial fibrillation (AF) usually causes the ventricles to contract faster than normal. When this happens, the ventricles don't have enough time to fill completely with blood to pump to the lungs and body. This inefficient pumping can cause signs and symptoms, such as:

• Palpitations (a strong feeling of a fast heartbeat or a "thumping" in the chest)
• Shortness of breath
• Weakness or difficulty exercising
• Chest pain
• Dizziness or fainting
• Fatigue (tiredness)
• Confusion

Complications

AF has two major complications - stroke and heart failure. Heart attack is another, rarer complication.

Stroke

During AF, the atria don't pump all of their blood to the ventricles. Some blood pools in the atria. When this happens, a blood clot (also called a thrombus) can form. If the clot breaks off and travels to the brain, it can cause a stroke. (A clot that forms in one part of the body and travels in the bloodstream to another part of the body is called an embolus.)

Blood-thinning medicines to reduce the risk of stroke are a very important part of treatment for patients who have AF.

Heart Failure

Heart failure occurs when the heart can't pump enough blood to meet the body's needs. Because the ventricles are beating very fast and aren't able to properly fill with blood to pump out to the body, AF can lead to heart failure.

Fatigue and shortness of breath are common symptoms of heart failure. A buildup of fluid in the lungs causes these symptoms. Fluid also can build up in the feet, ankles, and legs, causing weight gain.

Lifestyle changes, medicines, and sometimes special care (rarely, a mechanical heart pump or heart transplant) are the main treatments for heart failure.