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Atrial fibrillation - Background information
What is it?
- Atrial fibrillation (AF) is an arrhythmia.
- AF results from irregular, disorganized electrical activity in the atria. In many people, this is thought to arise from rapidly firing cells at the junction of the pulmonary veins in the left atrial musculature [BHF, 2004].
- The rapidly firing impulses cause disorganized atrial depolarization and ineffective atrial contractions [NICE, 2006].
- The atrioventricular node receives more electrical impulses than it can conduct. This results in an irregular ventricular rhythm; the ventricular rate of untreated AF often averages 160–180 beats per minute (although this is typically slower in elderly people) [AHA, 2006].
- AF is classified according to the pattern of episodes [Levy et al, 2003; Fuster et al, 2006a].
- Paroxysmal AF — episodes that last longer than 30 seconds but less than 7 days (often less than 48 hours) and are self-terminating and recurrent.
- Persistent AF — episodes lasting longer than 7 days (spontaneous termination of the arrhythmia is unlikely to occur after this time).
- Permanent AF — AF that fails to terminate using cardioversion, or is terminated but relapses within 24 hours, or longstanding AF (usually longer than 1 year) in which cardioversion has not been indicated or attempted (sometimes called accepted permanent AF).
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