A patient with Wolff-Parkinson-White (WPW) syndrome develops atrial fibrillation. Verapamil and digoxin are contraindicated. Which drug is the preferred treatment to terminate the AF and why?

• A Adenosine; it blocks AV conduction and terminates the accessory pathway reentry
• B Procainamide; it depresses conduction in the accessory pathway (Kent bundle) and slows ventricular rate ✓
• C Amiodarone; its broad-spectrum action blocks all pathways equally
• D Metoprolol; beta-blockade preferentially slows the accessory pathway

Explanation

In WPW with AF, verapamil and digoxin are contraindicated because blocking AV node conduction redirects impulses exclusively through the accessory pathway (Kent bundle), which has a shorter refractory period and can conduct at very rapid rates, potentially precipitating ventricular fibrillation. Procainamide (a class Ia antiarrhythmic) is preferred as it prolongs the refractory period of both the accessory pathway and the AV node, slowing conduction in the Kent bundle and reducing ventricular rate. IV procainamide or DC cardioversion is the standard of care. Adenosine blocks only the AV node and does not suppress accessory pathway conduction.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.