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Rhythm

Atrial flutter

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This is the date the draft was written, not a medical review date.

Atrial flutter is a macro-re-entrant atrial tachycardia, typically circulating around the tricuspid annulus. It gives regular sawtooth flutter waves with an atrial rate near 300 beats/min and, most often, 2:1 AV conduction.

ECG criteria

  • Regular atrial activity at about 300 beats/min in typical flutter.
  • Sawtooth flutter waves, best seen in II, III, aVF (negative in typical counter-clockwise flutter) and as positive deflection in V1.
  • Fixed AV conduction ratio, most often 2:1, giving a ventricular rate near 150 beats/min; 3:1 or 4:1 gives a slower rate.
  • Variable block produces an irregular ventricular response.
  • QRS usually narrow, with no isoelectric baseline between flutter waves.

Mechanism

A single large re-entrant circuit, in typical flutter confined to the right atrium around the tricuspid annulus and dependent on the cavotricuspid isthmus, drives the atria at a regular high rate. The AV node cannot conduct every impulse and passes a fixed fraction, commonly every second one.

Common causes

  • Structural heart disease, heart failure, hypertension and valvular disease.
  • Chronic lung disease and pulmonary embolism, with right atrial dilatation.
  • Previous cardiac surgery or atrial ablation (atypical or scar-related circuits).
  • Thyrotoxicosis, alcohol, acute illness; often coexists with atrial fibrillation.

Management principles

Principles mirror those of atrial fibrillation: assess stroke risk and the need for anticoagulation, control the rate or restore sinus rhythm, and treat underlying causes. Catheter ablation of the cavotricuspid isthmus is often highly effective for typical flutter; unstable patients follow the local advanced life support protocol, and local guidelines apply.

High-level principles for study. Treatment decisions follow local guidelines and the clinical situation.

Pitfalls and mimics

  • A regular narrow-complex tachycardia at about 150 beats/min should always prompt a search for flutter waves with 2:1 conduction; they are easily hidden in the T wave.
  • Vagal manoeuvres or adenosine transiently slow the ventricular rate and unmask flutter waves, helping diagnosis.
  • Flutter with variable conduction can be mistaken for atrial fibrillation, and coarse atrial fibrillation for flutter.

Practise in the ECG trainer — Recognise this pattern on generated tracings.

References

  1. 2019 ESC Guidelines for the management of patients with supraventricular tachycardia. European Society of Cardiology (2019) — Tier 2 (guidelines / primary literature)
  2. 2020 ESC Guidelines for the diagnosis and management of atrial fibrillation developed in collaboration with the European Association for Cardio-Thoracic Surgery (EACTS). European Society of Cardiology (2020) — Tier 2 (guidelines / primary literature)
  3. Wagner GS, Strauss DG. Marriott's Practical Electrocardiography. Wolters Kluwer, 12th edition (2013) — Tier 3 (textbook)

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