Causes of Atrial Fibrillation

Learn a little more about the causes of atrial fibrillation

To pump blood, your heart muscles must contract and relax in a coordinated rhythm. Contraction and relaxation are controlled by electrical signals that travel through your heart muscle.

 

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 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 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, the ventricles 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 overloaded with impulses trying to get through to the ventricles. The ventricles also beat rapidly, but not as rapidly as the atria. The reason is that the AV node is like a highway on-ramp — only so many cars 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 damages to the heart’s structure are the most common cause of atrial fibrillation. Possible causes of atrial fibrillation include:

* High blood pressure
* Heart attacks
* Abnormal heart valves
* Congenital heart defects
* An overactive thyroid 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
* Emphysema or other 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 slower. If you have atrial flutter, the abnormal heart 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 symptoms, causes and risk factors of atrial flutter are similar to those of atrial fibrillation. For example, strokes are a common concern in someone with atrial flutter. As with atrial fibrillation, atrial flutter is usually not life-threatening when it’s properly treated.

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