Clinical Notes : Cardiology

175. ECG - Atrial Fibrillation

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  • Irregularly irregular rhythm.

  • No P waves.

  • Absence of an isoelectric baseline.

  • Variable ventricular rate.

  • QRS complexes usually < 120 ms unless pre-existing bundle branch block, accessory pathway, or rate related aberrant conduction.

  • Fibrillatory waves may be present and can be either fine (amplitude < 0.5mm) or coarse (amplitude >0.5mm).

  • Fibrillatory waves may mimic P waves leading to misdiagnosis.

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Atrial fibrillation

Commonly AF is associated with a ventricular rate ~ 110 – 160.

AF is often described as having ‘rapid ventricular response’ once the ventricular rate is > 100 bpm.

‘Slow’ AF is a term often used to describe AF with a ventricular rate < 60 bpm.

Causes of ‘slow’ AF include hypothermia, digoxin toxicity, medications, and sinus node dysfunction.


Atrial Fibrillation

Dr Ed Burns,

Life in the Fast Lane

last update March 16, 2019


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