Atrial Fibrillation

Atrial fibrillation (AF) is a supraventricular arrhythmia.

ECG Recognition:

• It is seen as oscillations of low amplitude (f waves) at a rate of about 300-600 bpm. 
• These waves have variable amplitude, shape and timing. 
• Sometimes, f waves can mimic atrial flutter in V1. There is absence of uniform and regular atrial activity in other leads in AF compared to AFL. 
• In some, the f waves are so small. The diagnosis of atrial fibrillation on these patients will be based on the irregularly irregular ventricular activity. 
• Ventricular activity
• Irregularly irregular ventricular rhythm.
• About 100-160 bpm in the absence of drugs affecting the AV node.
• Typically called AF with rapid ventricular response (AF with RVR) if the ventricular rate is > 100 bpm and AF with slow ventricular response if ventricular rate is < 60 bpm.
• Can be more than 250 bpm in the presence accessory pathway in cases of Wolff-Parkinson-White (WPW) syndrome
• Can look regular when the rate is more than 170 bpm.
• Can be regular in cases of paced beats and complete heart block with regular escape beats.
• QRS can be narrow or wide if there is an existing bundle branch block or aberrancy.

Atrial fibrillation. Course fibrillatory waves seen in V1. 

Atrial fibrillation with rapid ventricular response. This is an irregularly irregular narrow QRS complex tachycardia at a rate of about 180 bpm. Coarse fibrillatory waves can be seen in V1.

Atrial fibrillation with slow ventricular response. Fine fibrillatory waves with ventricular rate of about 50 bpm (rate computed using the 6-second method).

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