Atrial Flutter
ECG Features
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Narrow Complex Tachycardia: Generally presents with a regular atrial activity at ~300 bpm.
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Isoelectric Baseline Loss: Absence of a flat baseline between waves.
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Saw-Tooth Pattern: Inverted flutter waves in leads II, III, aVF, and upright in V1.
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Ventricular Rate: Depends on AV conduction ratio.
Note: This pattern occurs due to anticlockwise reentry (90% cases).
AV Conduction Ratios
Fixed AV Conduction Ratio
- 2:1 Block: 150 bpm
- 3:1 Block: 100 bpm
- 4:1 Block: 75 bpm
Variable AV Conduction Ratio
- Irregular ventricular response, may mimic atrial fibrillation.
- Alternating 2:1, 3:1, and 4:1 conduction ratios can occur.
Pathophysiology
- Re-entry Circuit: Occurs within the right atrium, typically resulting in an atrial rate of ~300 bpm.
- Ventricular Rate: Determined by the AV conduction ratio.
- 1:1 Conduction: Can result in severe haemodynamic instability and is associated with ventricular fibrillation.
Note: The term AV block in atrial flutter implies a physiological response to rapid atrial rates.
Classification
Typical Atrial Flutter (Type I)
- Anticlockwise Reentry: Most common, inverted flutter waves in II, III, aVF.
- Clockwise Reentry: Positive flutter waves in II, III, aVF, broad inverted in V1.
Atypical Atrial Flutter (Type II)
- Does not meet typical criteria, associated with higher atrial rates and instability.
Recognition Tips
- Suspect flutter if narrow complex tachycardia at 150 bpm.
- Use vagal maneuvers or adenosine to reveal flutter waves.
- Check for identical R-R intervals along the strip for block patterns.
ECG Examples
- Example 1: Atrial Flutter with 2:1 Block, inverted waves in II, III, aVF.
- Example 2: Variable block, flutter waves in II, III, aVF.
- Example 3: 4:1 Block, slow ventricular response.
- Example 4: Variable block with clockwise reentry circuit.
- Example 5: High-grade AV block, possibly due to digoxin toxicity.
- Example 6: 1:1 block with rapid tachycardia, prioritize resuscitation.
- Example 7: 2:1 Block, narrow complex tachycardia.
- Example 8: 3:1 Block with negative flutter waves in inferior leads.
Related Topics
References
- Dr Smith’s ECG Blog
- ERCast Podcast on Atrial Flutter, Fibrillation and Ablation
- Studies on atrial flutter patterns and classifications.
Further Reading
- ECG Mastery Courses: Yellow, Blue, Black Belt
- ECG Textbooks and Clinical Interpretation Guides
- LITFL ECG Library and related resources
Authors
- Ed Burns: Emergency Physician with a focus on ECG interpretation.
- Robert Buttner: Advanced Trainee in Emergency Medicine with interests in ECGs and ultrasound.