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2288 pages added, reviewed or updated during the last month (last updated: 19/4/2021)

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atrial fibrillation (AF)

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Atrial fibrillation is a supraventricular tachyarrhythmia characterised by ineffective, chaotic, irregular and rapid (300 to 600 beats per minute) atrial activity resulting in the deterioration of atrial mechanical function (1). 

AF is the most common sustained cardiac arrhythmia seen in the general population (2)

  • in majority it is thought to be caused by rapidly firing cells located at the junction of the pulmonary veins with the left atrial musculature (3)
  • these rapidly firing impulses are responsible for disorganized atrial depolarization and ineffective atrial contractions
  • in turn, it results in an irregular ventricular rate because the impulses from the atria approach the atrioventricular node from varying angles and at varying intervals.

Atrial fibrillation is often seen in the elderly and generally is asymptomatic. If atrial fibrillation occurs when there is a large atrium, for example in mitral stenosis, then this is a predisposing factor to the development of thromboembolism.

Stroke risk

  • use the CHA2DS2-VASc stroke risk score to assess stroke risk in people with any of the following (4):
    • symptomatic or asymptomatic paroxysmal, persistent or permanent atrial fibrillation
    • atrial flutter
    • a continuing risk of arrhythmia recurrence after cardioversion back to sinus rhythm

Anticoagulation in chronic atrial fibrillation (4)

  • anticoagulation may be with apixaban, dabigatran etexilate, rivaroxaban or a vitamin K antagonist

    • consider anticoagulation for men with a CHA2DS2-VASc score of 1. Take the bleeding risk into account

    • offer anticoagulation to people with a CHA2DS2-VASc score of 2 or above, taking bleeding risk into account

    • do not offer stroke prevention therapy to people aged under 65 years with atrial fibrillation and no risk factors other than their sex (that is, very low risk of stroke equating to a CHA2DS2-VASc score of 0 for men or 1 for women)


  • do not offer aspirin monotherapy solely for stroke prevention to people with atrial fibrillation (4)


Last edited 05/2018 and last reviewed 08/2020