In WPW syndrome with acute arrhythmia, which drug is used to terminate the arrhythmia?

• A. Adenosine
• B. Procainamide
• C. Amiodarone
• D. Verapamil

Answer: (B)

In WPW with an acute tachyarrhythmia, the aim is to block conduction through the accessory pathway and disrupt the reentrant circuit. Procainamide is a class IA antiarrhythmic that blocks sodium channels and prolongs the refractory period, including in the accessory pathway. By lengthening the pathway’s refractory period, it terminates the tachycardia and prevents rapid ventricular rates, effectively converting the rhythm toward normal.

Why this works better than the others: adenosine and calcium channel blockers slow conduction through the AV node, which can paradoxically promote conduction over the accessory pathway and worsen the situation, potentially leading to dangerous rapid ventricular rates. Amiodarone is a backup option in some WPW scenarios, but procainamide is classically preferred for acute termination because of its direct effect on the accessory pathway and reentrant circuits.