What ECG (electrocardiogram) pattern is characterized by a shark tooth appearance?

Atrial Flutter: The Sawtooth ECG Pattern

Atrial flutter produces the characteristic "sawtooth" ECG pattern, most prominently visible in leads II, III, aVF, and V1, consisting of regular flutter (f) waves without an isoelectric baseline between deflections. 1, 2

ECG Characteristics of the Sawtooth Pattern

The sawtooth appearance in typical atrial flutter has specific morphologic features:

• The pattern consists of a downsloping segment, followed by a sharper negative deflection, then a sharp positive deflection with a positive 'overshoot' leading to the next downsloping plateau 1
• Flutter waves are most characteristically inverted in leads II, III, and aVF, and upright in lead V1 1
• The atrial rate typically ranges from 240-320 beats per minute 1, 2
• The relative size of each component can vary markedly between patients 1

Clinical Presentation and Ventricular Response

Atrial flutter commonly presents with 2:1 AV block, resulting in a regular ventricular rate of approximately 150 beats per minute (range 120-160 bpm) 1, 2

Key distinguishing features from atrial fibrillation:

• Unlike atrial fibrillation, atrial flutter shows organized atrial activity with a regular sawtooth pattern rather than chaotic fibrillatory waves 2
• The ventricular response in atrial flutter is typically regular (with fixed AV block ratios), whereas atrial fibrillation produces an irregularly irregular ventricular response 2

Reverse Typical Atrial Flutter

When the direction of atrial activation reverses (ascending the anterior wall and descending the posterior wall), flutter waves become upright in leads II, III, and aVF and inverted in lead V1 1

• This occurs in approximately 10% of clinical cases 1
• The reentry circuit remains the same, only the direction changes 1

Common Diagnostic Pitfalls

Atrial fibrillation may be misdiagnosed as atrial flutter when atrial activity is prominent on the ECG in more than one lead 1

Critical distinction: Atrial flutter maintains regular flutter waves without an isoelectric baseline, while other atrial tachycardias show discrete P waves separated by an isoelectric baseline in one or more leads 1

Clinical Context

Atrial flutter may arise during treatment with antiarrhythmic agents prescribed to prevent recurrent atrial fibrillation 1

• The ECG pattern may fluctuate between atrial flutter and atrial fibrillation, reflecting changing activation patterns in the atria 1
• Approximately 80% of patients who undergo radiofrequency catheter ablation of typical atrial flutter will develop atrial fibrillation within 5 years 2