A 45-year-old man with WPW syndrome develops atrial fibrillation with rapid ventricular response (260 bpm) showing irregular wide QRS complexes. Which drug is ABSOLUTELY CONTRAINDICATED?
- A IV procainamide
- B DC cardioversion
- C IV adenosine ✓
- D IV ibutilide
Correct answer: C. IV adenosine
Explanation
In WPW with AF (pre-excited AF), AV nodal blocking agents (adenosine, beta-blockers, calcium channel blockers, digoxin) are absolutely contraindicated. By blocking the AV node, they preferentially shunt conduction through the accessory pathway (shorter refractory period), dramatically increasing ventricular rate and risking degeneration to ventricular fibrillation. Procainamide (Class IA) is the drug of choice as it slows accessory pathway conduction. DC cardioversion is safe and preferred in unstable patients. Ibutilide can be used but procainamide is standard.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.