Atrial fibrillation

DEFINITION

At Mayo Clinic, we take the time to listen, to find answers and to provide you the best care.

Learn more. Request an appointment.

Atrial fibrillation is an irregular and often rapid heart rate that commonly causes poor blood flow to the body.

During atrial fibrillation, the heart’s two upper chambers (the atria) beat chaotically and irregularly — out of coordination with the two lower chambers (the ventricles) of the heart. Atrial fibrillation symptoms often include heart palpitations, shortness of breath and weakness.

Episodes of atrial fibrillation can come and go, or you may develop atrial fibrillation that doesn’t go away and may require treatment. Although atrial fibrillation itself usually isn’t life-threatening, it is a serious medical condition that sometimes requires emergency treatment. It can lead to complications. Atrial fibrillation may lead to blood clots forming in the heart that may circulate to other organs and lead to blocked blood flow (ischemia).

Treatments for atrial fibrillation may include medications and other interventions to try to alter the heart’s electrical system.

CAUSES

Atrial fibrillation is an irregular and often rapid heart rate that occurs when the two upper chambers of your heart (atria) experience chaotic electrical signals.

Your heart consists of four chambers — two upper chambers (atria) and two lower chambers (ventricles). Within the upper right chamber of your heart (right atrium) is a group of cells called the sinus node. This is your heart’s natural pacemaker. The sinus node produces the impulse that normally starts each heartbeat.

Normally, the impulse travels first through the atria and then through a connecting pathway between the upper and lower chambers of your heart called the atrioventricular (AV) node. As the signal passes from the sinus node through the atria, they contract, pumping blood from your atria into the ventricles below. As the signal passes through the AV node to the ventricles, it signals the ventricles to contract, pumping blood out to your body.

In atrial fibrillation, the upper chambers of your heart (atria) experience chaotic electrical signals. As a result, they quiver. The AV node — the electrical connection between the atria and the ventricles — is bombarded with impulses trying to get through to the ventricles. The ventricles also beat rapidly, but not as rapidly as the atria, as not all the impulses get through. The reason is that the AV node is like a highway on-ramp — only so many vehicles can get on at one time.

The result is a fast and irregular heart rhythm. The heart rate in atrial fibrillation may range from 100 to 175 beats a minute. The normal range for a heart rate is 60 to 100 beats a minute.

Possible causes of atrial fibrillation

Abnormalities or damage to the heart’s structure are the most common cause of atrial fibrillation. Possible causes of atrial fibrillation include:

• High blood pressure
• Heart attacks
• Coronary artery disease
• Abnormal heart valves
• Heart defects you’re born with (congenital)
• An overactive thyroid gland or other metabolic imbalance
• Exposure to stimulants, such as medications, caffeine or tobacco, or to alcohol
• Sick sinus syndrome — improper functioning of the heart’s natural pacemaker
• Lung diseases
• Previous heart surgery
• Viral infections
• Stress due to pneumonia, surgery or other illnesses
• Sleep apnea

However, some people who have atrial fibrillation don’t have any heart defects or damage, a condition called lone atrial fibrillation. In lone atrial fibrillation, the cause is often unclear, and serious complications are rare.

Atrial flutter

Atrial flutter is similar to atrial fibrillation, but the rhythm in your atria is more organized and less chaotic than the abnormal patterns common with atrial fibrillation. Sometimes you may have atrial flutter that develops into atrial fibrillation and vice versa.

The risk factors for and the symptoms and causes of atrial flutter are similar to those of atrial fibrillation. For example, strokes are also a concern in someone with atrial flutter. As with atrial fibrillation, atrial flutter is usually not life-threatening when it’s properly treated.

SYMPTOMS

A heart in atrial fibrillation doesn’t beat efficiently. It may not be able to pump enough blood out to your body with each heartbeat.

Some people with atrial fibrillation have no symptoms and are unaware of their condition until it’s discovered during a physical examination. Those who do have atrial fibrillation symptoms may experience signs and symptoms such as:

• Palpitations, which are sensations of a racing, uncomfortable, irregular heartbeat or a flip-flopping in your chest
• Weakness
• Reduced ability to exercise
• Fatigue
• Lightheadedness
• Dizziness
• Confusion
• Shortness of breath
• Chest pain

Atrial fibrillation may be:

• Occasional. In this case it’s called paroxysmal (par-ok-SIZ-mul) atrial fibrillation. You may have symptoms that come and go, lasting for a few minutes to hours and then stopping on their own.
• Persistent. With this type of atrial fibrillation, your heart rhythm doesn’t go back to normal on its own. If you have persistent atrial fibrillation, you’ll need treatment such as an electrical shock or medications in order to restore your heart rhythm.
• Permanent. In this type of atrial fibrillation, the normal heart rhythm can’t be restored. You’ll have atrial fibrillation permanently, and you’ll often require medications to control your heart rate. Most people with permanent atrial fibrillation will require blood thinners to prevent blood clots.

When to see a doctor

If you have any symptoms of atrial fibrillation, make an appointment with your doctor. Your doctor may order an electrocardiogram to determine if your symptoms are related to atrial fibrillation or another heart rhythm disorder (arrhythmia).

If you have chest pain, seek emergency medical assistance immediately. Chest pain could signal that you’re having a heart attack.