Atrial fibrillation

18 min read

What is atrial fibrillation?

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 doctor

You should make an appointment to see your doctor 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 doctor 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)
, 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
    (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

Symptoms of atrial fibrillation

Some people with atrial fibrillation, particularly older people, don't have any symptoms.

The abnormality in heart rhythm is often only discovered during routine tests or investigations for another condition.

Typically, a cardioversion (where the heart is given a controlled electric shock to restore normal rhythm) is carried out. At this point, many people feel much better and realise that they hadn't been feeling normal.

People often attribute tiredness and feeling lethargic to ageing, but once normal rhythm is restored, they realise that these symptoms were caused by atrial fibrillation.

Heart palpitations

The most obvious symptom of atrial fibrillation is heart palpitations – where your heart may feel like it's pounding, fluttering or beating irregularly, often for a few seconds or possibly a few minutes.

As well as an irregular heartbeat, your heart may also beat very fast (often considerably higher than 100 beats per minute).

You can work out your heart rate by checking the pulse in your neck or wrist.

Other symptoms you may experience if you have atrial fibrillation include:

  • tiredness, and being less able to exercise
  • breathlessness
  • feeling faint or lightheaded
  • chest pain

The way the heart beats in atrial fibrillation reduces the heart's performance and efficiency. This can lead to

low blood pressure (hypotension)
heart failure

You should see your doctor immediately if you notice a sudden change in your heartbeat and experience chest pain.

Causes of atrial fibrillation

The exact cause of atrial fibrillation is unknown, but it's 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's also associated with other medical conditions, including:

However, not everyone with atrial fibrillation has one of the conditions above. It can sometimes affect people who are physically very fit, such as athletes.

When no other conditions are associated with atrial fibrillation, it's known as lone atrial fibrillation.


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

  • drinking excessive amounts of alcohol, particularly
    binge drinking
  • being overweight (read about
    how to start losing weight
  • drinking lots of caffeine, such as tea, coffee or energy drinks
  • taking illegal drugs, particularly amphetamines or cocaine
  • smoking

Diagnosing atrial fibrillation

See your doctor immediately if you have chest pain and notice a sudden change in your heartbeat.

Checking your pulse

Follow the four steps below to check your pulse.

  • sit down for five minutes and avoid smoking or drinking caffeine before taking the reading
  • hold your left hand out with your palm facing up and elbow slightly bent
  • firmly place the index and middle finger of your right hand on your left wrist, at the base of the thumb (between the wrist and the tendon attached to the thumb)
  • using the second hand on a clock or watch, count the number of beats for 30 seconds, and then double that number to get your heart rate in beats per minute

At rest, a normal heart rate should be 60 to 100 beats per minute. In atrial fibrillation, the heart rate can often be considerably higher than 100 beats per minute and each individual beat is erratic.

Heart rhythm charity Arrythmia Alliance has further information on

knowing your pulse
and how to check it.

Checking and assessing your pulse can give you a good indication of whether you have atrial fibrillation, but a full medical investigation will be needed before a diagnosis can be made.

When to see your doctor

Make an appointment to see your doctor 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 )

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

If atrial fibrillation is suspected, your doctor may give you an electrocardiogram (ECG) and refer you to a heart specialist (cardiologist) for further tests.

A cardiologist who specialises in electrical disturbances of the heart is known as an electrophysiologist. They can carry out a procedure called catheter ablation to treat your atrial fibrillation.

Electrocardiogram (ECG)


is a test that records your heart's rhythm and electrical activity. It's usually carried out in a hospital or GP surgery, takes about five minutes and is painless.

During an ECG, 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 onto paper. During an episode of atrial fibrillation, your heart rate will be irregular and over 100 beats per minute.

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

However, as it can often be difficult to capture an episode of atrial fibrillation, you may be asked to wear a small, portable ECG recorder. The recorder will either trace your heart rate continuously over 24 hours, or when you switch it on at the start of an episode.

Other tests

If you have atrial fibrillation, a number of other tests should be carried out. These include:

  • an echocardiogram
    – which is an ultrasound scan of the heart; it can help to identify any other heart-related problems, and is used to assess the structure and function of the heart and valves
  • a chest X-ray – which can help to identify any lung problems that may be causing atrial fibrillation
  • blood tests
    – which can highlight anaemia, problems with kidney function, or an
    overactive thyroid gland (hyperthyroidism)

Atrial fibrillation treatment

Treatments for atrial fibrillation include medications to control heart rate and reduce the risk of stroke, and procedures such as cardioversion to restore normal heart rhythm.

It may be possible for you to be treated by your doctor or you may be referred to a heart specialist (a cardiologist). Some cardiologists, known as electrophysiologists, specialise in the management of abnormalities of heart rhythm.

You'll have a treatment plan and work closely with your healthcare team to decide the most suitable and appropriate treatment for you. Factors that will be taken into consideration include:

  • your age
  • you overall health
  • the type of atrial fibrillation you have
  • your symptoms
  • whether you have an underlying cause that needs to be treated

The first step is to try to find the cause of the atrial fibrillation. If a cause can be identified, you may only need treatment for this. For example, if you have an overactive thyroid gland (hyperthyroidism), medication to treat it may also cure atrial fibrillation.

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

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

You'll be promptly referred to your specialist treatment team if one type of treatment fails to control your symptoms of atrial fibrillation and more specialised management is needed.

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 medicines are available to restore normal heart rhythm, including:

  • flecainide
  • beta-blockers
    , particularly sotalol
  • amiodarone
  • dronedarone (only for certain people)

An alternative medication may be recommended if a particular medicine doesn't work or the side effects are troublesome.

Newer medicines are in development, but aren't widely available yet.

Controlling the rate of the heartbeat

The aim is to reduce the resting heart rate to under 90 beats per minute, although in some people the target is under 110 beats per 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 control the heart rate further. In some cases, amiodarone may be tried.

Normally, only one medication will be tried before catheter ablation (see below) is considered.

Side effects

As with any medicine, anti-arrhythmics can cause side effects. The most common side effects of anti-arrhythmics are:

  • beta-blockers – tiredness, coldness of hands and feet, low blood pressure, nightmares and
  • flecainide nausea, vomiting and heart rhythm disorders
  • verapamil
    , low blood pressure, ankle swelling and heart failure
  • 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 disappear when treatment is stopped)

Amiodarone can cause a wide range of serious side effects affecting the eyes, heart, lung, liver, thyroid gland, skin, and your nerves. Your doctor may perform tests of your blood (to check your liver and thyroid levels), lungs, heartbeat, and eyes before, during and after treatment – it’s important to have these tests because they can identify if there’s a problem.

See a doctor or go to a hospital straight away if you experience any of the following during treatment or in the period after stopping amiodarone:

  • new or worsening shortness of breath or coughing that will not go away
  • yellowing of the skin or eyes (jaundice), feeling tired or sick, loss of appetite, stomach pain, or high temperature
  • weakness, weight loss or weight gain, heat or cold intolerance, hair thinning, sweating, changes in menstrual periods, swelling of the neck (goitre), nervousness, irritability, restlessness, or decreased concentration
  • your heartbeat becomes even more uneven or erratic, or becomes very slow
  • any loss of eyesight

Read the patient information leaflet that comes with the medicine for more details.

Medicines to reduce the risk of a stroke

The way the heart beats in atrial fibrillation means there's a risk of

blood clots
forming in the heart chambers. If these enter the bloodstream, they can cause a

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

You may be given medication according to your risk of having a stroke. Depending on your level of risk, you may be prescribed

or a newer type of anticoagulant , such as dabigatran, rivaroxaban, apixaban or edoxaban (see below).

If you're prescribed an

, your risk of bleeding will be assessed both before you start the medication and while you're taking it.

Aspirin isn't recommended to prevent strokes caused by atrial fibrillation.


People with atrial fibrillation who have a high or moderate risk of having a stroke are usually prescribed warfarin , unless there's a reason they can't take it.

Warfarin is an anticoagulant, which means it stops the blood clotting. There's 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's important to take warfarin as directed by your doctor. If you're prescribed warfarin, you need to have regular blood tests and, after these, your dose may be changed.

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

While taking warfarin, you should be careful about drinking too much alcohol regularly and avoid binge drinking.

Drinking cranberry juice and grapefruit juice can also interact with warfarin and isn't recommended.

Alternative anticoagulants

Rivaroxaban, dabigatran, apixaban and edoxaban are newer anticoagulants and an alternative to warfarin.

The National Institute for Health and Care Excellence
(NICE) has approved these medicines for use in treating atrial fibrillation. NICE also states that you should be offered a choice of anticoagulation and the opportunity to discuss the merits of each medicine.

Unlike warfarin, rivaroxaban, dabigatran, apixaban and edoxaban don't interact with other medicines and don't require regular blood tests. In large trials, the medicines have been shown to be as effective or more effective than warfarin at preventing strokes and deaths. They also have a similar or lower rate of major bleeding.

You can read more about rivaroxaban, dabigatran and apixaban in the

NICE guidance about Atrial fibrillation: management

Edoxaban is recommended as an option for preventing stroke, heart disease and coronary artery disease in people with atrial fibrillation who have one or more risk factors, such as:

  • heart failure, high blood pressure or diabetes
  • a previous history of stroke or transient ischaemic attack (TIA)
  • aged 75 years or older

You can read the

NICE guidance
about Edoxaban for preventing stroke and systemic embolism in people with non-valvular atrial fibrillation.


Cardioversion may be recommended for some people with atrial fibrillation. It involves giving the heart a controlled electric shock to try to restore a normal rhythm.

Cardioversion is usually carried out in hospital so that the heart can be carefully monitored.

If you've had atrial fibrillation for more than two days, cardioversion can increase the risk of a clot forming. In this case, you'll be given an anticoagulant for three to four weeks before cardioversion, and for at least four weeks afterwards to minimise the chance of having a stroke. In an emergency, pictures of the heart can be taken to check for blood clots, and cardioversion can be carried out without going on medication first.

Anticoagulation may be stopped if cardioversion is successful. However, you may need to continue taking anticoagulation after cardioversion if the risk of atrial fibrillation returning is high and you have an increased risk of having 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's an option if medication hasn't 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.

The procedure usually takes two to three hours, so it may be carried out under

general anaesthetic
(which means you're asleep during the procedure).

You should make a quick recovery after having catheter ablation and be able to carry out most of your normal activities the next day. However, you shouldn't lift anything heavy for two weeks, and driving should be avoided for the first two days.



is a small, battery-operated device that's implanted in your chest, just below your collarbone. It's usually used to stop your heart beating too slowly, but in atrial fibrillation it may be used to help your heart beat regularly.

Having a pacemaker fitted is usually a minor surgical procedure carried out under a local anaesthetic (the area being operated on is numbed and you are awake during the procedure).

This treatment may be used when medicines aren't effective or are unsuitable. This tends to be in people aged 80 or over.

Complications of atrial fibrillation

People with atrial fibrillation are at increased risk of having a stroke. In extreme cases, atrial fibrillation can also lead to heart failure.


When the upper chambers of the heart (atria) don't pump efficiently, as in atrial fibrillation, there's a risk of blood clots forming.

These blood clots may move into the lower chambers of the heart (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 .

Atrial fibrillation increases the risk of a stroke by around four to five times. However, the risk depends on a number of factors, including age and whether you have high blood pressure (hypertension), 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, as your heart is unable to pump blood around your body efficiently.

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.