What medication should be given to a patient with Wolf-Parkinson-White (WPW) syndrome presenting with tachycardia and an electrocardiogram (ECG) showing atrial fibrillation (A-fib) with a wide QRS complex?

Management of WPW Syndrome with Atrial Fibrillation and Wide QRS Complex

The correct answer is B - Amiodarone, though procainamide or ibutilide are the preferred first-line agents according to ACC/AHA/ESC guidelines; amiodarone receives a Class IIb recommendation for hemodynamically stable patients with pre-excited atrial fibrillation. 1

Critical First Step: Assess Hemodynamic Stability

• If the patient is hemodynamically unstable (hypotensive, altered mental status, chest pain, acute heart failure), perform immediate electrical cardioversion to prevent ventricular fibrillation and sudden cardiac death 1, 2
• This patient with HR 250 and wide QRS complex in WPW with A-fib is at high risk for deterioration into ventricular fibrillation 1, 3

Pharmacologic Management for Stable Patients

First-Line Agents (Class I Recommendation)

• Intravenous procainamide is the preferred first-line pharmacologic agent for hemodynamically stable patients with WPW and pre-excited atrial fibrillation (wide QRS ≥120 ms) 1, 2
• Intravenous ibutilide is an equally acceptable first-line option 1, 2
• These agents work by slowing conduction through the accessory pathway and increasing its refractory period 4, 5

Second-Line Agents (Class IIb Recommendation)

• Intravenous amiodarone receives a Class IIb recommendation (may be considered) for hemodynamically stable patients with AF involving conduction over an accessory pathway 1, 2
• Other Class IIb options include quinidine and disopyramide 1

Absolutely Contraindicated Medications (Class III)

Never administer the following in WPW with pre-excited atrial fibrillation:

• Beta-blockers (Option A) - Contraindicated because they block the AV node but not the accessory pathway, potentially accelerating conduction through the bypass tract and precipitating ventricular fibrillation 1, 2, 6
• Calcium channel blockers (Option C) - Diltiazem and verapamil are absolutely contraindicated for the same mechanism 1, 2
• Digoxin (Option D) - Contraindicated as it can enhance conduction through the accessory pathway and trigger ventricular fibrillation 1, 2, 6

Why These Medications Are Dangerous

The pathophysiology is critical to understand: AV nodal blocking agents (beta-blockers, calcium channel blockers, digoxin) slow conduction through the normal AV node but do not affect the accessory pathway 1, 5. This creates preferential conduction down the accessory pathway, allowing extremely rapid ventricular rates that can degenerate into ventricular fibrillation and sudden cardiac death 1, 3.

Clinical Recognition Features

ECG findings that confirm pre-excited atrial fibrillation in WPW:

• Irregularly irregular rhythm (atrial fibrillation) 3, 7
• Very rapid ventricular rate (often >250 bpm) 8, 3
• Wide QRS complexes (≥120 ms) 1, 2
• Presence of delta waves (slurred QRS upstroke) 3, 7
• Bizarre, varying QRS morphology due to varying degrees of pre-excitation 3

Answer to the Multiple Choice Question

Among the four options provided:

• Option A (Beta-blocker) - Class III contraindication 1
• Option B (Amiodarone) - Class IIb recommendation (acceptable but not first-line) 1
• Option C (CCB) - Class III contraindication 1
• Option D (Digoxin) - Class III contraindication 1

Therefore, B (Amiodarone) is the only acceptable answer among the choices given, though it is important to note that procainamide or ibutilide would be preferred if available 1, 2.

Common Pitfalls to Avoid

• Do not assume all wide complex tachycardias are ventricular tachycardia - The triad of very rapid rate (>250 bpm), wide QRS, and irregular rhythm should raise suspicion for WPW with atrial fibrillation 8, 3
• Do not use adenosine when QRS is wide (≥120 ms) - Adenosine is only safe when QRS is narrow (<120 ms), indicating conduction through the AV node 1
• Do not delay cardioversion in unstable patients - Attempting pharmacologic conversion in an unstable patient wastes critical time 1

Definitive Management

After acute stabilization, catheter ablation of the accessory pathway is the definitive treatment (Class I recommendation) with >95% success rate and should be performed in all symptomatic WPW patients 1, 2, 6.