Which intravenous medication is most appropriate for a young female with Wolff‑Parkinson‑White syndrome presenting in atrial fibrillation with rapid ventricular response (~200 bpm) and wide QRS complexes?

Amiodarone is Contraindicated – Use Procainamide or Ibutilide

In a young female with WPW syndrome presenting with atrial fibrillation, wide QRS complexes, and rapid ventricular response (~200 bpm), the most appropriate intravenous medication is procainamide (Option C is incorrect; the answer should be procainamide, which is not listed, making amiodarone the least harmful of the options given, though still contraindicated). However, based on the options provided and guideline evidence, none of the listed medications (metoprolol, digoxin, amiodarone, or diltiazem) are appropriate first-line choices.

Critical Contraindications in WPW with Pre-excited AF

The wide QRS complexes indicate pre-excitation (conduction through the accessory pathway), which makes this a life-threatening emergency requiring specific management:

• AV nodal blocking agents are absolutely contraindicated in WPW patients with pre-excited atrial fibrillation, as they can accelerate conduction through the accessory pathway and precipitate ventricular fibrillation 1, 2, 3

• Specifically contraindicated medications include:

  • Metoprolol (Option A) – beta-blockers are Class III contraindicated 1, 2
  • Digoxin (Option B) – digitalis glycosides are Class III contraindicated 1, 2, 3
  • Diltiazem (Option D) – non-dihydropyridine calcium channel antagonists are Class III contraindicated 1, 2, 3

Amiodarone: Controversial but Not First-Line

Amiodarone (Option C) occupies a gray zone in the guidelines:

• The ACC/AHA guidelines list amiodarone as Class IIb (may be reasonable) for hemodynamically stable patients with AF involving an accessory pathway, but this is a weak recommendation 1, 3

• More recent Praxis Medical Insights explicitly state that amiodarone should be avoided in WPW patients with pre-excited AF, as it can accelerate the ventricular rate (Class III: Harm) 3

• The mechanism of harm is that amiodarone has AV nodal blocking properties that can facilitate antegrade conduction along the accessory pathway 1, 2, 3

Correct First-Line Therapy (Not Listed in Options)

The guideline-recommended medications are:

• Procainamide – Class I recommendation for stable patients with WPW and pre-excited AF 1, 3, 4
• Ibutilide – Class I recommendation as an alternative 1, 2, 3, 4

These agents work by slowing conduction through the accessory pathway itself, rather than blocking the AV node 2, 3, 4

Hemodynamic Status Determines Management

Since vital signs are not provided, you must assess:

• If the patient shows hemodynamic instability (hypotension, altered mental status, acute heart failure, ongoing chest pain), immediate electrical cardioversion is the treatment of choice, not pharmacological therapy 1, 3, 5

• If the patient is hemodynamically stable, proceed with intravenous procainamide or ibutilide 1, 3

Answering the Question as Asked

Given only the four options provided and forced to choose:

• Amiodarone (Option C) is the "least wrong" answer, though it carries significant risk and is not guideline-recommended as first-line therapy 1, 3

• The other three options (metoprolol, digoxin, diltiazem) are absolutely contraindicated and could precipitate ventricular fibrillation 1, 2, 3

Common Pitfalls

• Never assume wide-complex tachycardia is ventricular tachycardia in a young patient with palpitations – consider WPW with pre-excited AF 4, 6, 7

• The irregularity of the rhythm, very rapid rate (>200 bpm), and wide QRS complexes are classic ECG features of pre-excited AF in WPW 4, 7

• Administering AV nodal blockers can be fatal – they remove the "brake" on the accessory pathway and allow extremely rapid ventricular rates that degenerate into ventricular fibrillation 1, 2, 3, 6