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Pre-flecainide Exercise Testing — EECC MCQ

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ModerateArrhythmia & ElectrophysiologyPre-flecainide Exercise TestingEECC

A 65-year-old man with paroxysmal AF and normal LV function is prescribed flecainide for rhythm control. Before starting, his cardiologist orders an exercise stress test. Why?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Flecainide can slow atrial rate and organise AF into atrial flutter, which may conduct 1:1 during exercise — exercise testing unmasks this risk and also excludes underlying CAD, which is a contraindication to flecainide use

Before initiating flecainide (or propafenone), the 2024 ESC AF Guidelines recommend: (1) exclude structural heart disease (echocardiography) — flecainide is contraindicated in ischaemic heart disease, HFrEF, and significant LVH; (2) exclude CAD (exercise testing or imaging) — flecainide increases mortality in post-MI patients (CAST trial); (3) exercise testing to assess for: (a) use-dependent sodium channel block causing QRS widening at fast heart rates (flecainide slows conduction, and excessive QRS prolongation >25% of baseline at peak exercise indicates toxicity risk); (b) 1:1 flutter conduction during exercise (flecainide may organise AF into flutter with a slower atrial rate that can conduct 1:1 at the AV node during adrenergic stimulation). A rate-limiting agent (beta-blocker or diltiazem) must be co-prescribed to prevent 1:1 flutter conduction.

Reference: ESC (2024): AF Guidelines