Atrial flutter (AFL) is an arrhythmia that can be likened to a dog chasing its tail creating a circus movement (reentrant arrhythmia). The impulse travels from the interatrial septum to the right atrial free wall. The impulse can travel clockwise or counter-clockwise.
Figures A and B shows the simplified
counter-clockwise and clockwise movement of atrial flutter in the right atrium.
SVC - superior vena cava, IVC - inferior vena cava, TA - atrial septum
- Typical AFL waves are best seen in II, III and aVF (inferior leads) which have a regular rhythm, and constant morphology.
- There is a downsloping segment followed by a sharper negative deflection, and then a sharp positive deflection, with a positive overshoot leading to the next downsloping plateau (sawtooth).
- Typical clockwise is the inversion of the appearance in counter-clockwise AF with broad positive deflections in the inferior leads and a wide negative deflection in V1.
- Typical AFL rate is usually 240-340 bpm but can be slower in patients on antiarrhythmics, atrial myopathy or patients who had incomplete ablation.
- Most commonly there is 2:1 AV conduction but variable conduction (4:1 or 6:1) can be seen.
- The QRs morphology will look the same during sinus rhythm unless there is aberrancy.
Counter-clockwise atrial flutter with 2:1 AV conduction. Sawtooth pattern seen in
lead II and atrial rate best at 300 bpm and atrial activity best seen in V1.
Atrial flutter with variable AV conduction. Sawtooth pattern seen on lead II and atrial flutter rate best computed using PP interval in V1 with 1 big square (~300 bpm).
Clockwise atrial flutter unmasked by a properly-timed PVC. The 2 multifocal PVC exposed the hidden P waves (red arrows).
Atrial flutter with 4:1 AV conduction. This is a regular wide QRS complex rhythm at a ventricular rate of about 70 bpm with flutter waves. There are 4 flutter waves for every 1 QRS (4:1 AV conduction).
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