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 (bpm) when you're resting. In AF, the heart rate can sometimes be very fast (often between 140 and 180 bpm) as well as being irregular.
Why is it important to know about atrial fibrillation?
Some people with atrial fibrillation (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?
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?
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 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 (electrocardiogram, or ECG) confirms the diagnosis as long as it's performed during an episode of 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 (echocardiogram, or 'echo'). These tests look for an underlying cause of AF, such as a heart problem or an overactive thyroid gland.
Did you find this information useful?
- 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
- Thoracoscopic exclusion of the left atrial appendage in atrial fibrillation (with or without other cardiac surgery) for the prevention of thromboembolism, NICE Interventional Procedure Guideline (June 2011)
- Isaew A, Adderley NJ, Ryan R, et al; The treatment of paroxysmal atrial fibrillation in UK primary care. Heart. 2017 Jun 1. pii: heartjnl-2016-310927. doi: 10.1136/heartjnl-2016-310927.
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