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Flecainide-induced 1:1 Flutter — EECC MCQ

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ModerateArrhythmia & ElectrophysiologyFlecainide-induced 1:1 FlutterEECC

A 45-year-old man with paroxysmal AF maintained on flecainide 100 mg bd develops sustained atrial flutter with 1:1 conduction at a ventricular rate of 220 bpm. He presents with pre-syncope and hypotension. What has occurred and how should it be managed?

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Correct answer: E — Flecainide has organised AF into atrial flutter with a slower atrial rate (~220 bpm vs AF 400-600 bpm), which then conducts 1:1 through the AV node because flecainide's vagolytic effect enhances AV conduction — treat with urgent DC cardioversion and add or optimise rate-limiting agent

Class IC antiarrhythmics (flecainide, propafenone) can convert AF into atrial flutter by slowing the atrial rate (from chaotic 400-600 bpm to organised 200-250 bpm). The slower flutter rate can then conduct 1:1 through the AV node (unlike faster AF which creates functional AV node refractoriness), causing dangerously fast ventricular rates. This risk is compounded by: (1) flecainide's vagolytic effect (enhances AV conduction); (2) flecainide slowing ventricular conduction (wide QRS → haemodynamic compromise). Prevention: ALWAYS co-prescribe a rate-limiting agent (beta-blocker or non-DHP CCB) with flecainide (Class I recommendation in ESC AF Guidelines). Acute management: urgent DC cardioversion for haemodynamic compromise. IV isoprenaline or atropine may be needed for extreme bradycardia if cardioversion reveals underlying conduction disease.

Reference: ESC (2024): AF Guidelines