Which antiarrhythmic drug classes are preferred for medical prophylaxis of reentrant tachycardia in Wolff-Parkinson-White syndrome?

• A. IA or IC
• B. Class III only
• C. Class II only
• D. Vasopressors

Answer: (A)

In Wolff-Parkinson-White syndrome, reentrant tachycardias arise because of conduction through an accessory pathway that bypasses the normal AV node. To prevent recurrence, you want drugs that reduce conduction and increase the refractory period of that pathway, making it harder for the reentrant circuit to sustain itself. Sodium channel blockers in the Class I family, particularly the IA and IC agents, do exactly that. They slow conduction and lengthen refractory periods in the accessory pathway, which suppresses reentrant circuits and lowers the chance of recurrence.

Beta-blockers (Class II) or calcium channel blockers slow AV nodal conduction but don’t affect the accessory pathway, so they don’t reliably prevent reentry and can even worsen preexcitation in some scenarios, especially if atrial fibrillation courses rapidly down the pathway. Vasopressors don’t address the arrhythmia mechanism at all. Amiodarone (Class III) can be used in some WPW patients, but for medical prophylaxis of recurrent AVRT, Class I agents are preferred due to their more direct effect on the accessory pathway’s conduction and refractoriness. Therefore, using an IA or IC antiarrhythmic is the best choice.