April 23, 2014
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Atrial Fibrillation


What is atrial fibrillation?

Atrial fibrillation (also known as AF or AFib) is the most common type of arrhythmia (irregular heartbeat or heart rhythm). Many people are not aware of what atrial fibrillation is and refer to this heart rhythm problem as "heart flutter" or "irregular heartbeat." They may also call it "heart palpitations," which are the most common symptoms of atrial fibrillation.

To understand atrial fibrillation, you need to understand how the heart works and what a normal heartbeat is.

The normal heart
The heart is a muscle made up of 4 chambers: 2 atria (the left atrium and the right atrium, making up the top half of the heart) and 2 ventricles (left and right, making up the bottom half of the heart). The heart has its own electrical system that controls the rate and rhythm of the heartbeat. The heart beats at an average of 60 to 100 times per minute at rest.

heart

Figure 1

Click to enlarge

To get blood to reach the rest of the body, the heart's electrical system signals the chambers to work in coordination to expand and contract and to pump blood into the heart and out to the rest of the body. This starts with an electrical signal sent out by a group of cells called the sinus or sinoatrial (SA) node, the natural pacemaker of the heart. The SA is located in the right atrium.

Atrial fibrillation
In atrial fibrillation, arrhythmia (irregular heartbeat or heart rhythm) occurs because the electrical signal controlling the heartbeat becomes confused, and the atria quiver rapidly and unevenly, changing the constant rhythm of the heart.

The atria and ventricles no longer work in a coordinated way to contract and pump blood, the heart may not pump blood efficiently, and the heart rhythm becomes abnormal. In AF, the heart beats about 100 to 175 times per minute.

In our Human Atlas, you can see a video on atrial fibrillation.

There are three types of atrial fibrillation:

Paroxysmal: Paroxysmal AF is a temporary and sometimes recurrent condition that can start suddenly. The heartbeat returns to normal on its own within one week, without any medical assistance.

Persistent: In persistent AF, atrial fibrillation episodes last longer than one week and do not go away on their own. Medical assistance is required to return the heart rhythm to normal.

Permanent: In permanent AF, the irregular heartbeat lasts for a longer period of time (more than a year) and the heart rhythm does not return to normal even with medical assistance. Some people with permanent AF do not feel any symptoms.

Atrial fibrillation increases your risk for stroke, heart failure, and being hospitalized.

The good news is that AF is manageable and most people with AF can lead active, healthy, normal lives with appropriate treatment.

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