What is atrial fibrillation?

Atrial fibrillation is the most common type of abnormal heart rhythm. It may occur temporarily or be permanent. In atrial fibrillation, the heart beats irregularly and often too fast as well.

A healthy heart beats in time to its main pacemaker: the sinus node in the right atrium. At rest, it sends out 60 to 80 electrical signals per minute, which spread across both atria.

The AV node receives the individual signals and sends them along the conduction system, eventually causing the ventricles to contract.

In atrial fibrillation, the signals mainly come from the left atrium rather than from the sinus node. The signals then spread from there in a rapid and disorganized way. As a result, the atria no longer contract regularly, but instead twitch (or “fibrillate”) irregularly.

If the twitching were to spread to the ventricles, the heart would no longer be able to beat properly. The AV node acts as a sort of protective filter, ensuring that only some of the many signals are passed on to the ventricles.

Some people who have atrial fibrillation notice symptoms such as palpitations, while others don't have any symptoms at all. Without treatment, persistent atrial fibrillation can weaken the heart and increase the risk of a stroke.

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