Atrial fibrillation is a heart condition that causes an irregular and often abnormally fast heart rate.

A normal heart rate should be regular and between 60 and 100 beats a minute when you're resting. You can measure your heart rate by feeling the pulse in your neck or wrist.

In atrial fibrillation, the heart rate is irregular and can sometimes be very fast. In some cases, it can be considerably higher than 100 beats a minute.

This can cause problems including dizziness, shortness of breath and tiredness. You may be aware of noticeable heart palpitations, where your heart feels like it's pounding, fluttering or beating irregularly, often for a few seconds or, in some cases, a few minutes.   

Sometimes, atrial fibrillation doesn't cause any symptoms and a person with it is completely unaware that their heart rate isn't regular.

Read more about the symptoms of atrial fibrillation.

When to see your GP

You should make an appointment to see your GP if:

  • you notice a sudden change in your heartbeat
  • your heart rate is consistently lower than 60 or above 100 – particularly if you're experiencing other symptoms of atrial fibrillation, such as dizziness and shortness of breath   

See your GP as soon as possible if you have chest pain.

What causes atrial fibrillation?

When the heart beats normally, its muscular walls contract (tighten and squeeze) to force blood out and around the body. They then relax, so the heart can fill with blood again. This process is repeated every time the heart beats.

In atrial fibrillation, the heart's upper chambers (atria) contract randomly and sometimes so fast that the heart muscle can't relax properly between contractions. This reduces the heart's efficiency and performance.

Atrial fibrillation occurs when abnormal electrical impulses suddenly start firing in the atria. These impulses override the heart's natural pacemaker, which can no longer control the rhythm of the heart. This causes you to have a highly irregular pulse rate.

The cause isn't fully understood, but it tends to occur in certain groups of people (see below) and may be triggered by certain situations, such as drinking excessive amounts of alcohol or smoking.

Read more about the causes of atrial fibrillation.

Atrial fibrillation can be defined in various ways, depending on the degree to which it affects you. For example:

  • paroxysmal atrial fibrillation  episodes come and go, and usually stop within 48 hours without any treatment
  • persistent atrial fibrillation  each episode lasts for longer than seven days (or less when it's treated)
  • long-standing persistent atrial fibrillation  this means you have had continuous atrial fibrillation for a year or longer
  • permanent atrial fibrillation  atrial fibrillation is present all the time 

Who's affected?

Atrial fibrillation is the most common heart rhythm disturbance, affecting around one million people in the UK.

Atrial fibrillation can affect adults of any age, but it becomes more common as you get older. It affects about 7 in 100 people aged over 65, and more men than women have it. 

Atrial fibrillation is more likely to occur in people with other conditions, such as high blood pressure (hypertension), atherosclerosis, or a heart valve problem.

Treating atrial fibrillation

Atrial fibrillation isn't usually life-threatening, but it can be uncomfortable and often requires treatment.

Treatment may involve: 

  • medication to prevent a stroke (people with atrial fibrillation are more at risk of having a stroke)
  • medication to control the heart rate or rhythm
  • cardioversion  where the heart is given a controlled electric shock to restore normal rhythm
  • catheter ablation  where the area inside the heart that's causing the abnormal heart rhythm is destroyed using radiofrequency energy; you may then need to have a pacemaker fitted to help your heart beat regularly

Read more about treating atrial fibrillation and the possible complications of atrial fibrillation.

Atrial flutter

Atrial flutter is less common than atrial fibrillation, but shares the same symptoms, causes and possible complications. Around a third of people with atrial flutter also have atrial fibrillation.

Atrial flutter is similar to atrial fibrillation, but the rhythm in the atria is more organised and less chaotic than the abnormal patterns caused by atrial fibrillation.

Treatment for atrial flutter is also slightly different, because catheter ablation (see above) is considered to be the best treatment, whereas medication is often the first treatment used for atrial fibrillation.

Page last reviewed: 18/05/2015

Next review due: 18/05/2017