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There are several kinds of irregular heartbeat. The one we look at here is called atrial fibrillation.

It can last for less than two days (called acute atrial fibrillation), or it can come and go. It may last for a long time (chronic atrial fibrillation).¹

Your heart has four main parts (called chambers). The two smaller chambers at the top of your heart are called the left atrium and the right atrium. Blood enters your heart by flowing into these top chambers, which pump it onwards into the two bigger, lower chambers.

The two lower chambers of your heart are called the left ventricle and the right ventricle. Their job is to pump blood out of your heart and around your body.

The right ventricle pumps blood to the lungs and the left ventricle pumps blood to the rest of the body.

The top-right chamber of your heart (right atrium) contains a control area (the pacemaker), which sends an electrical signal to make the muscles in the heart contract to push the blood through it.

If you have atrial fibrillation, the pacemaker sends out too many electrical signals at once. This makes the muscles of right atrium and left atrium contract far too fast, and means that the ventricles then pump blood out in an irregular way. This results in a very fast, irregular heart beat.

Some people are more likely to have atrial fibrillation than others. For example, men are one and a half times more likely to get it than women.²

Other things that can increase your risk of atrial fibrillation are:³

• Getting older
• High blood pressure
• Heart disease
• Heart attack
• Heart failure
• Heart valve problems
• Diabetes
• Too much alcohol
• Lung disorders
• Thyroid gland disorders.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.