Atrial fibrillation (AF) is an abnormal fast irregular heartbeat. An abnormal heartbeat rhythm is called an arrhythmia. A normal heart rate is between 60 and 100 beats a minute when you're resting. In atrial fibrillation, the heart rate can sometimes be very fast (often between 140 and 180 beats per minute) as well as being irregular.
Some people with AF don't have any symptoms and don't know they've got it. Even without symptoms, it's important to diagnose AF because the abnormal rhythm can cause blood clots to form in the heart. Most people with AF need to take a medicine to thin the blood to stop any blood clot from forming. If a clot does form then it may travel in the blood vessels to your brain and cause a stroke.
What causes it?
Atrial fibrillation (AF) is caused by a problem with the heart's conduction system. There are many different causes of AF. For more general information about the heart's conduction system, see separate leaflet called Abnormal Heart Rhythms (Arrhythmias).
In AF, the normal controlling timer in the heart is overridden by many random electrical impulses that fire off from the heart muscle. This causes the heart to contract between 140 and 180 times a minute. The ventricles contract in an irregular way and also with varying force.
AF is often divided into three types:
- Paroxysmal (which comes and goes).
- Persistent (lasts longer than seven days).
- Permanent (which doesn't go away).
How common is it?
Atrial fibrillation (AF) is common but mainly occurs in older people. Just under 2 in every 100 people in England have AF and the numbers are rising because of the increasing numbers of elderly people. AF is uncommon in younger people unless they have certain heart conditions.
What are the symptoms?
Many people with atrial fibrillation (AF) have no symptoms, particularly if their heart rate is not very fast. The AF may then be diagnosed by chance when a doctor or nurse feels your pulse. Your pulse rate may be fast, the rhythm is irregular and the force of each beat can vary.
Any symptoms usually start suddenly, soon after the AF develops. Possible symptoms include:
- A 'thumping' heart (palpitations). This means that you become aware of your heart. You may feel it beating in a fast and irregular way.
- Chest pains (angina) may develop. The pains tend to occur when you exert yourself but they may also occur even when you are resting.
- Breathlessness is often the first symptom that develops. It may occur all the time but you may become breathless just when you exert yourself, such as when you walk up stairs.
Do I need any tests?
- A heart tracing called an electrocardiogram (ECG) confirms the diagnosis as long as it's performed during an episode of atrial fibrillation (AF). Sometimes a 24-hour ECG is needed if your AF comes and goes and the resting ECG has not shown it.
- You will usually have other tests such as blood tests and an ultrasound scan of the heart, called an echocardiogram. These tests look for an underlying cause of AF, such as a heart problem or an overactive thyroid gland.
What are the different types of atrial fibrillation?
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.
Types of atrial fibrillation
There are three different types of 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 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 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.
What are the causes of atrial fibrillation?
In about 1 in 10 cases of AF there is no apparent cause. The heart is otherwise fine and there are no other diseases to account for it. This is called lone AF.
There are many conditions that may cause AF, including the following:
- High blood pressure is the most common cause. High blood pressure puts a strain on the heart muscle.
- AF is a common complication of various heart conditions. For example:
- AF is a complication of coronary heart disease. Coronary heart disease is the condition that causes chest pains (angina) and heart attacks and is common in older people.
- Various other heart problems may also trigger AF to develop. For example, AF occurs in some people with heart valve problems, pericardial disease, dilated cardiomyopathy and hypertrophic cardiomyopathy.
- Other conditions and situations that may trigger AF to develop include:
What are the treatment options for atrial fibrillation?
The treatment for AF either controls the heart rate or changes the rhythm back to normal. Because of the risk of blood clots forming and causing a stroke, the treatment also usually includes medication to prevent blood clots (anticoagulation).
Rate control treatment
In untreated AF, the heart rate may be as fast as 180 beats per minute, although it is more commonly between 120 and 160 beats per minute. The aim of medication is to bring the heart rate back down to normal (ideally, to less than 90 beats per minute when resting). If your heart rate is brought down to normal, your heart becomes efficient again and your symptoms usually improve. Your pulse may still feel irregular but not fast.
Several medicines can slow the heart rate down. They include beta-blocker medicines (such as atenolol and propranolol), calcium-channel blocker medicines (such as diltiazem and verapamil) and digoxin. These medicines work by interfering with the electrical impulses of the heart. The medicine chosen may depend on factors such as other heart problems that you may have.
Treatment is usually successful but the dose needed can vary from person to person. Also, in some people a combination of medicines may be needed if the heart rate is not brought down low enough with a single medicine.
Rhythm control treatment
Rhythm control means reverting the erratic heartbeat back to a normal regular rhythm. This is called cardioversion.
One method of cardioversion is to give your heart an electric shock. Another method is to use a medicine that may convert the heart rhythm back to a regular beat. One medicine used for rhythm control is amiodarone. Both of these methods have only limited success. Within a year after cardioversion, the heart has reverted back to AF in about half of cases.
Cardioversion is more likely to be considered as a possible option in certain situations - for example:
- If your AF has developed recently.
- If you are younger than 65 years.
- If an underlying cause for the AF has been successfully treated.
- If you have no other heart abnormality.
- If you have acute heart failure or unstable angina which is being made worse by the irregular heartbeat of AF.
A newer technique that may be used to restore the heart rhythm is called catheter ablation. A long, thin wire (catheter) is passed into the chambers of the heart via a large blood vessel in a leg. The tip of the catheter can destroy tiny sections of heart tissue that may be the cause of the abnormal electrical impulses.
What is anticoagulation treatment?
All people with atrial fibrillation (AF) - except those with the lowest risk of having a stroke - should be offered anticoagulation treatment. Anticoagulation means that you take a medicine to reduce the chance of forming a blood clot and having a stroke.
Aspirin was used in the past for preventing strokes if you have AF but is not as effective as warfarin and is just as likely to cause problems. Aspirin is therefore no longer recommended.
Other treatments may be advised, depending on the need to treat any underlying problems such as chest pains (angina), heart valve problems, high blood pressure (hypertension) or an overactive thyroid gland (hyperthyroidism).
What are the complications of atrial fibrillation?
An increased risk of having a stroke (or other blood clot problem)
The main complication of AF is an increased risk of having a stroke. AF causes turbulent blood flow in the heart chambers. This sometimes leads to a small blood clot forming in a heart chamber.
A clot can travel through the blood vessels until it becomes stuck in a smaller blood vessel in the brain (or sometimes in another part of the body). Part of the blood supply to the brain may then be cut off, which causes a stroke.
The individual risk of developing a blood clot and having a stroke depends on various factors. The level of risk can be calculated by your doctor using a set of specific questions. This will help to decide what treatments are required. All people except those at the lowest risk will be offered medication to help prevent clots from forming.
Less common complications of AF include the following:
- Heart failure - this develops in some cases. See separate leaflet called Heart Failure for more details.
- Weakness of the heart muscle (dilated cardiomyopathy). The reason why cardiomyopathy develops in some people with AF is not clear. See separate leaflet called Dilated Cardiomyopathy for more details.
- If you already have chest pains (angina), the chest pains may become worse if you have AF.
AF can also reduce the amount of exercise you're able to do. It has also been shown that AF can affect some brain functions like memory, attention and reasoning. AF can therefore have a big effect on your quality of life.
Further reading & references
- Management of atrial fibrillation; NICE Clinical Guideline (June 2014)
- 2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS; European Society of Cardiology (2016)
- Atrial Fibrillation; NICE CKS, October 2015 (UK access only)
- WatchBP Home A for opportunistically detecting atrial fibrillation during diagnosis and monitoring of hypertension; NICE Medical Technologies Guidance, January 2013
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Colin Tidy
Dr Hannah Gronow