Causes of Atrial Fibrillation

Authored by Dr Colin Tidy, 21 Sep 2017

Patient is a certified member of
The Information Standard

Reviewed by:
Dr Adrian Bonsall, 21 Sep 2017

In about 1 in 10 cases of AF there is no apparent cause. The heart is otherwise fine and there are no diseases to account for it. This is called lone AF.

There are many conditions that may cause AF, including the following:

In AF, the normal controlling timer in the heart is overridden by many random electrical impulses that fire off from the heart muscle in the atria. The atria then fibrillate. This means that the atria only partially squeeze (contract) - but very rapidly (up to 400 times per minute).

Only some of these impulses pass through to the ventricles and they do so in a very random and haphazard way. Therefore, the ventricles contract anywhere between 50 and 180 times a minute but usually between 140 and 180 times a minute. The ventricles contract not only in an irregular way but also with varying force.

For more information, see separate leaflet called Abnormal Heart Rhythms (Arrhythmias).

Types of atrial fibrillation


There are three different types of AF:

Paroxysmal AF

  • Paroxysmal AF means that you have episodes of AF that come and go.
  • Each episode comes on suddenly but will also stop suddenly without treatment within seven days (usually within two days). The heartbeat then goes back to a normal rate and rhythm.
  • The period of time between each episode (each paroxysm) can vary greatly from case to case.
  • Although paroxysmal AF means that it will stop on its own, some people with paroxysmal AF take treatment to stop it as quickly as possible after it starts.

Persistent AF

  • Persistent AF lasts longer than seven days and is unlikely to revert back to normal without treatment. However, the heartbeat can be reverted back to a normal rhythm with treatment.
  • Persistent AF tends to come and go so it may come back again at some point after successful treatment.

Permanent AF

  • Permanent AF is long-term and the heartbeat does not return back to a normal rhythm.
  • This may be because treatment has been tried and was not successful, or because treatment has not been tried.
  • People with permanent AF are treated to bring their heart rate back down to normal but the rhythm remains irregular.

Further reading and references

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