About atrial fibrillation

Atrial fibrillation (AF) is a condition that causes an irregular heart rate.

Most commonly, the heart rate will be unusually fast with this condition; but it is possible for the heart rate to be within accepted limits or slower and still be in atrial fibrillation. 

You can measure your heart rate by feeling the pulse in your wrist or neck. A normal heart rate, when you are resting, should be between 60 and 100 beats a minute. In atrial fibrillation, it may be over 140 beats a minute.

How is atrial fibrillation defined?

Atrial fibrillation is defined in various ways, depending on how it affects you:

  • paroxysmal atrial fibrillation - this comes and goes, usually stopping within 48 hours without any treatment.
  • persistent atrial fibrillation - this lasts for longer than seven days, or less when it is treated.
  • longstanding persistent atrial fibrillation - this means you have had continuous atrial fibrillation for a year or longer.
  • permanent atrial fibrillation - this is when atrial fibrillation is present all the time and no more attempts to restore normal heart rhythm will be made 

What happens in 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.

Atrial fibrillation occurs when abnormal electrical impulses suddenly start firing in the atria (upper chambers of the heart).

These impulses override the heart's natural pacemaker, which can no longer control the rhythm of the heart. The atria contract randomly and sometimes so fast that the heart muscle cannot relax properly between contractions. This reduces the heart's efficiency and performance and causes a highly irregular pulse rate.

What are the symptoms of atrial fibrillation?

Atrial fibrillation can lead to a number of problems, including:

  • dizziness
  • feeling faint
  • shortness of breath
  • fast and irregular heartbeat (palpitations)
  • feeling very tired

Some people with atrial fibrillation have no symptoms and are completely unaware that their heart rate is irregular.

Find out more about the symptoms of atrial fibrillation

Why does atrial fibrillation happen and how common is it?

Atrial fibrillation is the most common heart rhythm disturbance and affects up to 800,000 people in the UK.

The cause of atrial fibrillation is not fully understood, but it tends to occur in certain groups of people and may be triggered by certain situations, such as drinking excessive amounts of alcohol or smoking.

The condition can affect adults of any age or gender but:

  • is more common the older you get
  • affects about 10% of people over 75
  • more common in men than women

Atrial fibrillation is more likely to occur in people with other conditions, like:

  • high blood pressure
  • diabetes 
  • coronary heart disease

Find out more about the causes of atrial fibrillation and how it's diagnosed

What is the outlook with atrial fibrillation?

Atrial fibrillation is generally not life threatening, many people live normal healthy lives with this condition, but it can be uncomfortable and often needs treatment.

This condition increases your risk by about four to five times of having a transient ischaemic attack (TIA) or stroke.

This is because when the atria in the heart do not contract properly there is a risk of blood clot formation. Clots from the atria may break off and go to other parts of the body. A blood clot passing up to the arteries supplying the brain may cause a stroke.

For this reason, treatment may involve medication to control the heart rate or rhythm, and medication to prevent clots from forming in the blood.

Find out how to treat atrial fibrillation and possible complications of having AF

Symptoms of atrial fibrillation

The most obvious symptom of atrial fibrillation (AF) is palpitations caused by a fast and irregular heartbeat.

A normal heart rate, when you are resting, should be between 60 and 100 beats a minute. In atrial fibrillation, it may be over 140 beats a minute.

If you notice an irregular heartbeat and/or have chest pain, see your doctor immediately.

How to check your heart rate

You can check your heart rate by pressing gently on the pulse in your wrist or neck.

Other symptoms

As well as a fast and irregular heartbeat, you may also experience:

  • tiredness (inability to carry out  normal exercise for you)
  • breathlessness 
  • dizziness
  • feeling faint
  • palpitations
  • chest discomfort or pain

Some people have no symptoms

Some people with atrial fibrillation have no symptoms and it is only discovered during routine tests or investigations for another condition.

Causes of atrial fibrillation

The exact cause of atrial fibrillation (AF) is unknown, but it becomes more common with age and affects certain groups of people more than others.

People with other heart conditions

Atrial fibrillation is common in people with other heart conditions, such as:

  • high blood pressure 
  • coronary heart disease
  • heart valve disease
  • congenital heart disease (heart defects at birth)
  • heart failure (from any cause)

People with other medical conditions

Atrial fibrillation is also associated with other medical conditions such as:

Cause is unknown

Not everyone with atrial fibrillation falls into one of the above groups. Sometimes the cause can be idiopathic (no known cause) and can affect extremely athletic people.


Sometimes there is a trigger to an episode of atrial fibrillation, including:

  • drinking excessive amounts of alcohol, particularly binge drinking
  • being overweight 
  • taking illegal drugs, particularly amphetamines or cocaine
  • smoking
  • heightened emotional stress

Diagnosing atrial fibrillation

Feeling your pulse to check if you have an irregular heartbeat can give a strong indication of whether you have atrial fibrillation (AF). However, a complete diagnosis requires a full medical investigation.

If you notice your heartbeat is irregular and/or you have chest pain, see your GP straight away.

If your GP thinks you have atrial fibrillation after assessing your symptoms, you will be asked to have an electrocardiogram (ECG) and referred to a heart specialist, known as a cardiologist.

Electrocardiogram (ECG)

An ECG is a test that records the rhythm and electrical activity of your heart.

Small stickers called electrodes are attached to your arms, legs and chest and connected by wires to an ECG machine.

Every time your heart beats, it produces tiny electrical signals. An ECG machine traces these signals on paper.

An ECG is usually carried out in a hospital or GP surgery. It takes about five minutes and is painless.

If you have the test during an episode of atrial fibrillation, the ECG will record your abnormal heart rate. This will confirm the diagnosis of atrial fibrillation and rule out other conditions.

However, it may be difficult to capture an episode, as the irregular rhythm may 'come and go', therefore, to capture this your GP or cardiologist, may ask you to wear a small, portable ECG recorder for a longer period of time away from the hospital or GP surgery.

Find out more about having an ECG

Echocardiogram (Echo)

An echocardiogram, sometimes called an echo, is an ultrasound scan of the heart.

It can help identify any other heart problems and assess the structure and function of your heart and valves.

Find out more about having an echocardiogram

Chest X-ray

A chest X-ray may be performed and will identify any lung problems that may have caused the atrial fibrillation.

Blood tests

Blood tests can also be useful in the diagnosis of atrial fibrillation. They may show anaemia, which could be complicating the situation, problems with kidney function or hyperthyroidism (overactive thyroid gland).

Treating atrial fibrillation

The treatment of atrial fibrillation (AF) varies from person to person and depends on:

  • the type of atrial fibrillation 
  • symptoms 
  • treatment of any underlying cause
  • age
  • overall health

Some people may be treated by their GP, whereas others may be referred to a cardiologist.

Finding an underlying cause

The first step is to try to find out the cause of the atrial fibrillation. If a cause is found, treatment for this may be enough.

For example, medication to correct hyperthyroidism (an overactive thyroid gland) may cure atrial fibrillation.

If there is no underlying cause found

If no underlying cause of the atrial fibrillation can be found, the treatment options are:

  • medicines to control atrial fibrillation
  • restoring a normal heart rhythm
  • medicines to reduce the risk of a stroke
  • cardioversion (a controlled electrical shock to reset the heart rhythm)
  • catheter ablation
  • having a pacemaker fitted

You can find out more about each of these below.

Medicines to control atrial fibrillation

Medicines called anti-arrhythmics can control atrial fibrillation by:

  • restoring a normal heart rhythm
  • controlling the rate at which the heart beats

The choice of anti-arrhythmic medicine depends on:

  • the type of atrial fibrillation
  • any other medical conditions you have
  • side effects of the medicine chosen
  • how well the atrial fibrillation responds.

Some people with atrial fibrillation may need more than one anti-arrhythmic medicine to control it.

Restoring a normal heart rhythm

There are a number of drugs that can be used to try to restore a normal heart. The best option for you will be decided by your cardiologist and /or GP. 

Commonly, these drugs include:

Dronedarone may also be used for certain people.

It is important you know what side effects to look out for if taking such medication and seek medical advice if you experience any of them. 

To find out about side effects, read the patient information leaflet that comes with your medicine for more details. 

Medicines to reduce the risk of a stroke

The way the heart beats in atrial fibrillation means that there is a risk of blood clots forming in the heart chambers. If these get into the bloodstream, they can cause a stroke (our complications of atrial fibrillation section has more information on this).

Your doctor will assess your risk to minimise your chance of a stroke. They will consider your age and whether you have a history of any of the following:

You will be classed as having a high, moderate or low risk of a stroke and will be given medication according to your risk.

Depending on your level of risk, you may be prescribed warfarin.


Anticoagulants help to reduce the risk of stroke in patients with atrial fibrillation. Newer anticoagulants like apixaban, dabigatran, edoxaban and rivoroxaban are now more commonly used than warfarin. They do not require dose changes and continuous blood test monitoring.

Warfarin may still be used in patients who can't be treated with a newer anticoagulant, or in those patients with other conditions where treatment with warfarin is preferred.


Cardioversion may be tried in some people with atrial fibrillation. The heart is given a controlled electric shock to try to restore a normal rhythm.

The procedure normally takes place in hospital with heavy sedation or anaesthetic and careful monitoring.

In people who have had atrial fibrillation for more than two days, cardioversion is associated with an increased risk of clot formation. If this is the case, warfarin is given for three to four weeks before cardioversion and for at least four weeks afterwards to minimise the chance of having a stroke.

If the cardioversion is successful, warfarin may be stopped. However, some people may need to continue with warfarin if there is a high chance of their atrial fibrillation returning and they have a moderate to high risk of a stroke.

Catheter ablation

Catheter ablation is a procedure that very carefully interrupts abnormal electrical circuits. It is an option if medication has not been effective or tolerated.

Catheters (thin, soft wires) are guided through one of your veins into your heart where they record electrical activity.

When the source of the abnormality is found, an energy source (such as high-frequency radiowaves that generate heat) is transmitted through one of the catheters to destroy the tissue.

This procedure commonly takes two to three hours, so it may be done under general anaesthetic, where you are put to sleep.

Find out more about catheter ablation for atrial fibrillation on the Arrhythmia Alliance website

Having a pacemaker fitted

A pacemaker is a small, battery-operated device that is implanted in your chest, just below your collarbone.

It will not cure, reverse or actively treat your atrial fibrillation. 

A pacemaker provides beats where your heart is not supplying its own. If your heart beat is very slow the pacemaker will override this and pace at a set rate. If there are significant pauses between your heart beats beats, the pacemaker will supply a beat, acting as a 'safety net'.

Having a pacemaker fitted is usually a minor surgical procedure performed under a local anaesthetic (where the area is numbed).

Complications of atrial fibrillation

When the upper chambers of the heart, called the atria, do not pump efficiently then there is a risk of blood clots forming.

These blood clots may move into the lower chambers of the heart, called the ventricles, and get pumped into the blood supply to the lungs or the general blood circulation.


Clots in the general circulation can block arteries in the brain, causing a stroke.

The risk of a stroke in people with atrial fibrillation (AF) is four to five times greater than the general population. However, the risk depends on a number of factors, including age, whether you have high blood pressure, heart failure, diabetes and a previous history of blood clots.

Heart failure

If your atrial fibrillation is persistent, it may start to weaken your heart muscle.

In extreme cases, it can lead to heart failure, where your heart cannot pump blood around your body as efficiently as before.

Last updated:
17 May 2023