Atrial fibrillation
Atrial fibrillation Content Supplied by NHS Choices

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

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

Atrial fibrillation may be defined in various ways, depending on the degree to which it affects you:

  • Paroxysmal atrial fibrillation - this comes and goes and usually stops 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 usually lasts for longer than a year.
  • Permanent atrial fibrillation - this is present all the time and there are no more attempts to restore normal heart rhythm.

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.

In atrial fibrillation, the upper chambers of the heart, called 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.

This may lead to a number of problems, including dizziness and shortness of breath. You may also be aware of a fast and irregular heartbeat (palpitations) and feel very tired.

Read more about the symptoms of atrial fibrillation.

Some people with atrial fibrillation have no symptoms and are completely unaware that their heart rate is not regular. 

Why it happens

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 is not 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.

How common is atrial fibrillation?

Atrial fibrillation is the most common heart rhythm disturbance and affects up to 500,000 people in the UK.

Who is affected?

Atrial fibrillation can affect adults of any age. However, it affects more men than women and becomes more common the older you get. It affects about 10% of people over 75.

Atrial fibrillation is more likely to occur in people with other conditions, such as high blood pressure or atherosclerosis.

It is not common in younger people, but may be slightly more common in people with another heart condition, such as a heart valve problem.


Atrial fibrillation is generally not life threatening, but it can be uncomfortable and often needs treatment.

Treatment may involve medication to control the heart rate or rhythm, and medication to prevent a stroke.

Find out more about treatment for atrial fibrillation.

Symptoms of atrial fibrillation

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

The most obvious symptom of atrial fibrillation is a fast and irregular heartbeat, usually over 140 beats a minute. You can determine your heart rate by feeling the pulse in your wrist or neck.

You may also experience:

The way the heart beats in atrial fibrillation reduces the heart's efficiency and performance. This can result in low blood pressure and heart failure.

If you notice a sudden change in your heartbeat and have chest pain, see your doctor immediately.

Causes of atrial fibrillation

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

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

It is also associated with other medical conditions:

Not everyone with atrial fibrillation falls into one of the above groups. For example, it can affect extremely athletic people.


Certain situations can trigger an episode of atrial fibrillation, including:

  • drinking excessive amounts of alcohol, particularly binge drinking
  • being overweight
  • drinking lots of caffeine, such as tea, coffee or energy drinks
  • taking illegal drugs, particularly amphetamines or cocaine
  • smoking 
Diagnosing atrial fibrillation

If you notice a sudden change in your heartbeat and you have chest pain, see your GP straight away.

Feeling your pulse can give a strong indication of whether you have atrial fibrillation, but a complete diagnosis requires a full medical investigation.

If your GP thinks you have atrial fibrillation after assessing your symptoms, they may ask you to have an electrocardiogram and refer you to a heart specialist, known as a cardiologist.


An electrocardiogram (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. During atrial fibrillation, your heart rate is irregular and may be over 140 beats a minute.

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 attack 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 attack, so your GP may ask you to wear a small, portable electrocardiogram recorder. This will either trace your heart rate continuously over 24 hours, or when you switch it on at the start of an attack.


An echocardiogram is an ultrasound scan of the heart. It can help identify any other heart problems and assess the structure and function of the heart and valves.

Chest X-ray

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

Blood tests

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

Treating atrial fibrillation

The treatment of atrial fibrillation 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 heart specialist, known as a cardiologist.

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

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

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

  • medicines to control atrial fibrillation
  • medicines to reduce the risk of a stroke
  • cardioversion (electric shock treatment)
  • catheter ablation
  • having a pacemaker fitted

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 and 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

A variety of drugs are available to restore normal heart rhythm. These include:

New drugs are in development that may restore normal heart rhythm, but they are not widely available yet. If a particular drug does not work or the side effects are troublesome, another may be tried.

Controlling the rate of the heartbeat

The aim is to reduce the resting heart rate to under 90 beats a minute, although in some people the target is under 110 beats a minute.

A beta-blocker (such as bisoprolol or atenolol) or a calcium channel blocker (such as verapamil or diltiazem) will be prescribed.

A medicine called digoxin may be added to help further control the heart rate. In some cases, amiodarone may be tried.

Side effects

As with any medicine, anti-arrhythmics can cause side effects. Read the patient information leaflet that comes with the medicine for more details.

The most common side effects of anti-arrhythmics are:

  • beta-blockers: tiredness, coldness of hands and feet, low blood pressure, nightmares and impotence
  • flecainide: nausea, vomiting and heart rhythm disorders
  • amiodarone: sensitivity to sunlight (high-protection sunscreen must be worn or skin covered up), lung problems, changes to liver function or thyroid function (regular blood tests can check for this) and deposits in the eye (these go away when treatment is stopped)
  • verapamil: constipation, low blood pressure, ankle swelling and heart failure

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 (see complications of atrial fibrillation for more information).

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:

  • stroke or blood clots
  • heart valve problems
  • heart failure
  • high blood pressure
  • diabetes
  • heart disease

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 or aspirin.


People with atrial fibrillation who have a high or moderate risk of a stroke are usually prescribed warfarin, unless there is a reason they cannot take it.

Warfarin is an anticoagulant, which means it stops the blood from clotting. There is an increased risk of bleeding in people who take warfarin, but this small risk is usually outweighed by the benefits of preventing a stroke.

It is very important to take warfarin as directed by the doctor. People on warfarin need to have regular blood tests and, following these, their dose may be changed.

Many medicines can interact with warfarin and cause serious problems, so check that any new medicines are safe to take with warfarin.

Drinking more than moderate amounts of alcohol or drinking cranberry juice can also affect your warfarin and is not recommended.


People with atrial fibrillation who have a low risk of a stroke are likely to be given a low dose of aspirin to take every day instead of warfarin.

People who are unable to take warfarin may also be given aspirin instead.


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, where the heart is carefully monitored.

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 after cardioversion if there is a high chance of their atrial fibrillation returning and they have a moderate to high risk of a stroke (see above).

Catheter ablation

Catheter ablation is a procedure that very carefully destroys the diseased area of your heart and 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.

For more detailed information on catheter ablation for atrial fibrillation, go to 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 is usually used to prevent your heart rate going too slowly, but in atrial fibrillation it may help your heart beat regularly.

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

This treatment may be used when medicines are not effective or are unsuitable.

Find out more about pacemaker implantation.

Complications of atrial fibrillation


When the upper chambers of the heart, called the atria, do not pump efficiently, as in atrial fibrillation, 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 is about double that of the general population. However, the risk depends on a number of factors, including age and 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. In extreme cases, it can lead to heart failure, where your heart cannot pump blood around your body efficiently.

Frances, 57, was diagnosed with paroxysmal atrial fibrillation and keeps her heart rate under control with flecainide.

"I went to bed as normal one day and woke in the early hours feeling very strange. 

"My heart was beating heavily and I had a feeling similar to stomach rumbling, but it was in my chest. I could feel this across the upper part of my chest, including the top of my arm. I wasn't worried as it didn't hurt, and I drifted in and out of sleep.

"By 11am the next day, it was still going on, so I phoned the doctor. He told me to get a taxi to the surgery straight away, but I walked instead. Halfway there, I started to feel unwell and thought I was going to pass out.

"Once I'd made it to the doctor's, I didn't feel too bad. My GP took my pulse and straight away said that I had an arrhythmia, which is an irregular heartbeat.

"He wired me up to an electrocardiogram (ECG) and managed to capture my arrhythmia on the printout. Apparently, this can come and go quite quickly.

"I was given a high dose of aspirin, to lower my risk of getting a stroke, and was referred to hospital immediately. By the time I reached hospital, my symptoms had stopped. Luckily, the doctors could see from my previous ECG that I had an arrhythmia and diagnosed me with paroxysmal atrial fibrillation.

"They made an appointment for me to have a 24-hour ECG, which records heart symptoms as you go about your normal daily activities, and then I was discharged.

"In the meantime, I had two more episodes of atrial fibrillation and had to come back to hospital. I was given an intravenous infusion of flecainide, which corrects an abnormal heartbeat. I was only on the drip for 10 minutes when the monitor showed my heartbeat going back to normal. I've been on low-dosage tablets of flecainide ever since.

"When my appointment came for the 24-hour ECG, I felt perfectly well. Since I've been on the tablets, I haven't had anything like those three episodes.

"I also take aspirin daily to protect me from a stroke. Every day I experience extra heartbeats called ectopic beats, but they're nothing to worry about."

Rupert, 78, is a theatre director and regularly goes to the gym. In 2007, he was diagnosed with paroxysmal atrial fibrillation, but because he has no adverse symptoms, he goes about his life normally.

"It was after a gym session a year ago, when I took my pulse, that I realised something was wrong.

"I was quite surprised at the irregularity of my heartbeat. It went boom, boom, boom-boom-boom boom. I was concerned so I saw my GP and he referred me to a consultant cardiologist.

"The consultant did an angiogram, a thallium test (which shows how well blood flows to the heart) and an ECG (electrocardiogram) on me. My heart appeared to be in fairly good condition but the ECG showed that I had an irregular heartbeat. I was diagnosed with paroxysmal atrial fibrillation.

"I was prescribed the drug warfarin to lower my risk of getting a stroke, but no other medication.

"Then I heard about the heart charity Arrhythmia Alliance. They put me in touch with the Atrial Fibrillation Association, who were particularly helpful, and I learned a lot about atrial fibrillation through them. 

"Unlike many other people with atrial fibrillation, I have no adverse symptoms, which is puzzling. Apparently, different people react to arrhythmia in different ways. I've no idea what's caused my atrial fibrillation, but I am being treated for high blood pressure. I have a check-up with my GP every month.

"Atrial fibrillation hasn't stopped me from working as a theatre director. In fact, it hasn't affected my life at all."

See what the doctor sees with Map of Medicine

The Map of Medicine is used by doctors throughout the NHS to determine the best treatment options for their patients. NHS Choices offers everyone in England exclusive and free access to this cutting-edge internet resource, which lets you see exactly what your doctor sees.

The information in the Map has been approved by the UK's leading clinical experts, is based on the best available clinical evidence, and is continually updated. To take advantage of this unique resource go to:

Map of Medicine: atrial fibrillation

Map of Medicine: anticoagulation


The list below is a combination of the and brand names of medicines available in the UK. Each name provides a link to a separate website (Medicine Guides) where you can find detailed information about the medicine. The information is provided as part of an on-going medicine information project between NHS Direct, Datapharm Communications Ltd and other organisations.

The medicines listed below hold a UK licence to allow their use in the treatment of this condition. medicines are not included.

The list is continually reviewed and updated but it may not be complete as the project is still in progress and guides for new medicines may still be in development.

If you are taking one of these medicines for a different condition, or your medicine for this condition is not mentioned here at all, speak to your prescriber, GP or pharmacist, or contact NHS Direct on 0845 46 47.

Health Advice
Site Menu
News Letter