A 50-year-old woman with paroxysmal atrial fibrillation (CHA₂DS₂-VASc score 3) is in sinus rhythm on rate control. She prefers rhythm control. Flecainide is chosen. Which condition would CONTRAINDICATE flecainide use?
- A Paroxysmal AF with normal cardiac function and no structural heart disease
- B Structural heart disease (post-MI or LV dysfunction) ✓
- C Thyroid-induced AF in euthyroid patients
- D Lone AF in patients under 60 years
Explanation
Flecainide and propafenone are Class IC antiarrhythmics recommended only for AF in patients with NO structural heart disease (normal LVEF, no prior MI, no significant LV hypertrophy). The CAST trial demonstrated that Class IC drugs (flecainide, encainide) significantly increased mortality in post-MI patients with asymptomatic ventricular ectopy due to proarrhythmia—converting non-lethal VT to lethal ventricular arrhythmias. In structural heart disease or impaired LV function, Class III agents (amiodarone, sotalol, dofetilide) are used for rhythm control. This is a critical contraindication to remember.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.