Atrial flutter vs Atrial fibrillation
How to tell Atrial flutter and Atrial fibrillation apart when a board question makes them look alike.
Step 2 CK pairs are in open beta while clinical review finishes. Spot an issue? Tell us.
Sawtooth flutter waves with a near-regular ventricular rhythm around 150/min identifies atrial flutter.
Side by side
Regular narrow-complex tachycardia near 150/min with classic sawtooth flutter waves from macroreentrant right atrial rhythm.
Irregularly irregular rhythm without discrete P waves due to chaotic atrial depolarization.
Atrial flutter is usually a cavotricuspid-isthmus reentry circuit generating atrial rates around 300/min.
Atrial fibrillation results from multiple reentrant wavelets and ectopic atrial foci causing disorganized atrial activation.
ECG shows flutter waves best in II, III, aVF with atrial rate 240-340/min and often fixed 2:1 AV conduction yielding ventricular rate about 150/min.
ECG shows absent organized P waves, irregularly irregular R-R intervals, and variable ventricular response usually 90-170/min.
The trap
Atrial flutter with variable block can appear irregular and be mislabeled as fibrillation; careful inspection of inferior leads for repeating flutter waves changes rhythm diagnosis and ablation planning.
The repair move
Next best step: if unstable perform synchronized cardioversion immediately; if stable control ventricular rate with IV diltiazem or beta blocker, assess anticoagulation by CHA2DS2-VASc, and plan rhythm control or ablation based on duration and symptoms.
Try a free question
CoreA 61-year-old woman has sudden palpitations. BP 118/70 mm Hg, HR 152/min, oxygen saturation 98%. ECG reveals regular narrow-complex tachycardia with sawtooth waves in leads II, III, and aVF. What is the most likely diagnosis?
Show answer and explanation
Answer: A. Atrial flutter. Sawtooth atrial activity with regular ventricular response near 150/min is classic for atrial flutter with 2:1 conduction.
Why the other choices are tempting
- B. Incorrect because atrial fibrillation lacks organized flutter waves and is irregularly irregular.
- C. Incorrect because AVNRT usually has hidden retrograde P waves, not continuous sawtooth activity.
- D. Incorrect because multifocal atrial tachycardia shows at least three P-wave morphologies with irregular rhythm.
- E. Incorrect because sinus tachycardia has normal upright P waves preceding each QRS.
Flashcards
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Which ECG clue most quickly separates atrial flutter from atrial fibrillation?
Sawtooth flutter waves, often with ventricular rate near 150/min, favor atrial flutter.
How does the ventricular rhythm pattern differ in atrial fibrillation?
Atrial fibrillation produces an irregularly irregular R-R interval without consistent P waves.
Quick answers
What is the fastest way to tell Atrial flutter from Atrial fibrillation?
Sawtooth flutter waves with a near-regular ventricular rhythm around 150/min identifies atrial flutter.
What is the key clue for Atrial flutter?
Regular narrow-complex tachycardia near 150/min with classic sawtooth flutter waves from macroreentrant right atrial rhythm.
What is the key clue for Atrial fibrillation?
Irregularly irregular rhythm without discrete P waves due to chaotic atrial depolarization.
What is the common trap with Atrial flutter vs Atrial fibrillation?
Atrial flutter with variable block can appear irregular and be mislabeled as fibrillation; careful inspection of inferior leads for repeating flutter waves changes rhythm diagnosis and ablation planning.