Typical atrial flutter

Introduction

Atrial flutter is a type of supraventricular tachycardia which originates from a macro-re-entrant circuit in the atria. The atrial rate is typically between 250-350 beats/min with 2:1 conduction ratio the ventricular rate is 150 beats/min.

Conduction to ventricles:

• AV node cannot conduct at rates greater than 200 bpm > ventricular rate is a fraction of atrial rate
• 2:1 conduction – most often in atrial flutter, ventricular rate around 150 bpm
• 3:1 conduction – ventricular rate around 100 bpm

Atrial flutter usually starts with trigger beats that initiate the arrhythmia.

Classification

Types of atrial flutter depend on anatomical position and direction of the macro-re-entrant circuit.

Typical atrial flutter - common (counter-clockwise) and reverse (clockwise)

Typical atrial flutter involves counterclockwise, or less commonly clockwise, conduction in the right atrium in a circuit around the cavotricuspid isthmus (tissue that lies between the tricuspid valve annulus and the inferior vena cava). 

Counter-clockwise typical flutter (Common typical flutter)

• most common type, 90% of typical atrial flutters
• F waves – typical sawtooth pattern
• negative flutter waves in inferior leads (II, III, aVF)
• positive F waves in lead V1 (these may resemble broad P waves)

Clockwise typical flutter (Reverse typical flutter)

• the ECG image is reversed
• positive flutter waves in inferior leads (II, III, aVF) 
• inverted flutter waves in lead V1 (often broad, resembling P waves)
• this type is hard to distinguish from atypical flutter

‍ECG findings:

• Narrow complex tachycardia at a rate around 150 bpm
• Rate does not change over time
• Typical sawtooth pattern = flutter waves best seen in the inferior leads II, III, aVF
• Absence of isoelectric baseline 
• in rates >150 bpm it can be difficult to identify flutter waves. To slow ventricular response, use vagal maneuvers or medication to slow AV node conduction (adenosine, verapamil)

Picture 1 Mechanism and electrocardiographic pattern of typical atrial flutter (left) and reverse typical atrial flutter (right)

García Cosío F, Pastor A, Núñez A, Magalhaes AP, Awamleh P. Flúter auricular: perspectiva clínica actual [Atrial flutter: an update]. Rev Esp Cardiol. 2006 Aug;59(8):816-31. Spanish. PMID: 16938231.

ECG 1 Typical counter-clockwise atrial flutter

Typical atrial flutter with variable AV-block

• narrow complex typical flutter with ventricular rate at 85 bpm
• variable AV block raging from 1:1 to 4:1
• negative flutter waves in II, III, aVF

• positive flutter waves in V1

ECG 2 Typical clockwise atrial flutter

‍

• narrow complex atrial flutter with ventricular rate at 74 bpm
• positive flutter waves in inferior leads II, III, aVF
• negative flutter waves in lead V1
• absence of isoelectric baseline

ECG 3 Typical counter-clockwise atrial flutter

Typical atrial flutter with 4:1 conduction

• atrial rate 250 bpm with 4:1 conduction to ventricles at rate 63 bpm
• typical negative flutter waves in inferior leads II, III, aVF
• positive flutter waves in lead V1

ECG 4 Adenosine demasking typical atrial flutter

        Typical atrial flutter with conduction 1:1 and ventricular rate at 250 bpm

• adenosine completely blocks the AV node for 5–10 s and slow-downs the ventricular rate while revealing classical flutter waves.

Causes

• Typical atrial flutter has a strong anatomical dependence
• Related to atrial fibrillation and often coexisting in the same patients

Management

- Decreasing atrioventricular (AV) nodal conduction physiologically with a vagotonic maneuver (such as the Valsalva maneuver or carotid sinus massage) or with a rapidly acting drug (such as verapamil, or metoprolol/esmolol) will increase the AV nodal block and reveal the atrial F waves.

‍Acute therapy

1. Hemodynamically unstable patient – urgent synchronized cardioversion
2. Hemodynamically stable – diagnostic use of adenosine and pharmacological termination or cardioversion

 Adenosine

- is useful for diagnostic purposes, - by decreasing atrioventricular (AV) nodal conduction with a vagotonic maneuver or with adenosine the atrial F waves are revealed

  - AV node is not involved in the flutter circuit = adenosine does not terminate the rhythm

  Pharmacological termination

- i.v. ibutilide or i.v. or oral dofetilide (in-hospital) are recommended for conversion to sinus rhythm

  Synchronized cardioversion

- Low-energy (75 J)

  High-rate atrial pacing

- might be considered for termination of atrial flutter in the presence of an implanted pacemaker or defibrillator

  Rate control therapy (not often successful)

- Beta blockers - i.v. esmolol, i. v. metoprolol

- Calcium channel blockers (verapamil/diltiazem i.v.)

Chronic therapy

- Catheter ablation – recommended for all symptomatic or recurrent atrial flutters

- Beta-blockers or non-dihydropyridine calcium channel blockers (verapamil/diltiazem or beta blocker) should be considered if ablation is not desirable or feasible

Anticoagulation

• patients with atrial fibrillation, atrial flutter or any supraventricular tachycardia are at risk of thrombus formation and thromboembolism 
• effective anticoagulation is recommended in acute settings pre-cardioversion as well as chronic oral anticoagulation in persistent arrhythmias
• to estimate embolic risk use CHA2DS2-VASc scoring system
• to estimate bleeding risk use HAS-BLED risk score
• oral anticoagulants – warfarin, NOAC (dabigatran, apixaban rivaroxaban, edoxaban)
• parenteral anticoagulants – unfractionated heparin or low molecular weight heparin

Picture 2 Treatment of atrial flutter as per ESC guidelines

References

1. Camm, AJ, Luscher, T F, Serruys, PW. (2009). The ESC textbook of cardiovascular medicine. Oxford, Oxford University Press
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3. Strauss, David G., et al. Marriott's Practical Electrocardiography. Wolters Kluwer, 2021
4. Bibas, Lior et al. “Diagnosis and management of supraventricular tachycardias.” CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne vol. 188,17-18 (2016): E466-E473. doi:10.1503/cmaj.160079
5. https://litfl.com/atrial-flutter-ecg-library/
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7. García Cosío F, Pastor A, Núñez A, Magalhaes AP, Awamleh P. Flúter auricular: perspectiva clínica actual [Atrial flutter: an update]. Rev Esp Cardiol. 2006 Aug;59(8):816-31. Spanish. PMID: 16938231.