Atrial Fibrillation

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This is part of: Supraventricular Rhythms

Atrial fibrillation
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Atrial frequency	400-600 bpm
Ventricular frequency	75-175 bpm
Regularity	irregular
Origin	atria (SVT)
P-wave	absent
Effect of adenosine	reduces heart rate
Example: {{{example}}}
Another example: {{{example2}}}
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During atrial fibrillation the atria show chaotic depolarisation with multiple foci. Mechanically the atria stop contracting after several days to weeks of atrial fibrillation, the result of the ultra-rapid depolarisations that occur in the atria, typically around 400 bpm, but up to 600 bpm. At the AV node 'every now and then' a beat is conducted to the ventricles, resulting in an irregular ventricular rate, which is the typical ECG characteristic of atrial fibrillation. Sometimes atrial fibrillation results in a course atrial flutter wave on the ECG, but the baseline can also be flat. A flat baseline is more often seen in long standing atrial fibrillation. The cardiac stroke volume is reduced by 10-20% during atrial fibrillation, as the 'atrial kick' is missing and because the heart does not have time to fill at the often higher ventricular rate. Causes age (+- 10% of 70+ year olds and 15% of 90+ year olds have AFIB ^[1]), ischemia, hyperthyreoidism, alcohol abuse.

Atrial fibrillation can be catechorized as follows:

First documented episode
Recurrent atrial fibrillation: after two or more episodes.
Paroxysmal atrial fibrillation: if recurrent atrial fibrillation spontaneously converts to sinus rhythm.
Persisting atrial fibrillation: if an episode of atrial fibrillation persists more than 7 days.
Permanent atrial fibrillation: if atrial fibrillation persists after an effort of electrical or chemical cardioversion

Lone AF is atrial fibrillation in patients younger than 60 years in whom no clinical or electrocardiographic signs of heart or lung disease are present. These patiens have a favourable prognosis regarding thrombo-embolic events.

Non-valvular atrial fibrillation is atrial fibrillation in patients without heart valve disease or heart valve replacement or repair. ^[2]

Treatment strategies include:^[3]^[4]^[5]

Rate control: accept atrial fibrillation and focus on symptom relief and prevention of tachycardias. Typically with beta-blockers and digoxin. Target rate is < 100 bpm.
Rhythm control: trying to keep the patient in normal sinus rhythm. Typically with anti-arrhythmics like amiodarone, flecainide, and sotalol, or electrical cardioversion, or with radiofrequency catheter ablation.

In both cases anti-coagulants are needed to prevent embolic stroke.