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Atrial fibrillation (AF or A-fib) is the most common cardiac arrhythmia (abnormal heart rhythm)[1] and involves the two upper chambers (atria) of the heart. Its name comes from the fibrillating (i.e., quivering) of the heart muscles of the atria, instead of a coordinated contraction. It can often be identified by taking a pulse and observing that the heartbeats don't occur at regular intervals. However, a stronger indicator of AF is the absence of P waves on an electrocardiogram (ECG or EKG), which are normally present when there is a coordinated atrial contraction at the beginning of each heart beat.[2] Risk increases with age, with 8% of people over 80 having AF.

In AF, the normal electrical impulses that are generated by the sinoatrial node are overwhelmed by disorganized electrical impulses that originate in the atria and pulmonary veins, leading to conduction of irregular impulses to the ventricles that generate the heartbeat. The result is an irregular heartbeat, which may occur in episodes lasting from minutes to weeks, or it could occur all the time for years. The natural tendency of AF is to become a chronic condition. Chronic AF leads to a small increase in the risk of death.[3][4]

Atrial fibrillation is often asymptomatic and is not in itself generally life-threatening, but it may result in palpitations, fainting, chest pain, or congestive heart failure. People with AF usually have a significantly increased risk of stroke (up to 7 times that of the general population). Stroke risk increases during AF because blood may pool and form clots in the poorly contracting atria and especially in the left atrial appendage (LAA).[5] The level of increased risk of stroke depends on the number of additional risk factors. If a person with AF has none, the risk of stroke is similar to that of the general population.[6] However, many people with AF do have additional risk factors and AF is a leading cause of stroke.[7]

Atrial fibrillation may be treated with medications which either slow the heart rate or revert the heart rhythm back to normal. Synchronized electrical cardioversion may also be used to convert AF to a normal heart rhythm. Surgical and catheter-based therapies may also be used to prevent recurrence of AF in certain individuals. People with AF are often given anticoagulants such as warfarin to protect them from stroke.

Atrial fibrillation/flutter

 
URL of this page: http://www.nlm.nih.gov/medlineplus/ency/article/000184.htm

Atrial fibrillation/flutter is a heart rhythm disorder (arrhythmia). It usually involves a rapid heart rateheart rate that is not regular.

Causes

Causes

ArrhythmiasArrhythmias are caused by problems with the heart's normal electrical conduction system.

Normally, the four chambers of the heart (two atria and two ventricles) contract (squeeze) in an orderly way. When this happens, your heart is able to pump the blood your body needs without working any harder than it needs to.

The electrial impulse that signals your heart to contract begins in the sinoatrial node (also called the sinus node or SA node). This node is your heart's natural pacemaker.

  • The signal leaves the SA node and travels through the two upper chambers (atria).
  • Then the signal passes through another node (the AV node), and finally, through the lower chambers (ventricles).

In atrial fibrillation, the electrical impulse of the heart is not regular. The atria are contracting very quickly and not in a regular pattern. This makes the ventricles beat abnormally, leading to an irregular (and usually fast) pulse. As a result, the heart may be working harder and may no longer be able to pump enough blood.

In atrial flutter, the ventricles may beat very fast, but in a regular pattern.

If the atrial fibrillation/flutter is part of a condition called sick sinus syndrome, the sinus node may not work properly. The heart rate may alternate between slow and fast. As a result, there may not be enough blood to meet the needs of the body.

Atrial fibrillation can affect both men and women. It becomes more common with increasing age.

Causes of atrial fibrillation include: