In patients with WPW syndrome, verapamil can have what effect on conduction?

In patients with WPW syndrome, verapamil can have what effect on conduction?

• A. It always prevents tachyarrhythmias
• B. It has no effect on conduction
• C. It may increase conduction of the accessory pathways
• D. It slows conduction uniformly in the heart

Answer: (C)

In WPW, there is an extra conduction pathway that directly connects the atria to the ventricles, bypassing the normal AV node route. Verapamil blocks calcium channels, which slows conduction primarily through the AV node and lengthens its refractory period. Because the AV node is inhibited while the accessory pathway remains unaffected, impulses are more likely to travel via the accessory pathway relative to the AV node. This can increase conduction down the accessory pathway, especially during rapid atrial rhythms, and can lead to dangerously high ventricular rates or even malignant arrhythmias. So, verapamil may increase conduction through the accessory pathways rather than reliably preventing tachyarrhythmias. It does not slow conduction uniformly across the heart, and it does have a significant effect on AV nodal conduction.

In WPW, there is an extra conduction pathway that directly connects the atria to the ventricles, bypassing the normal AV node route. Verapamil blocks calcium channels, which slows conduction primarily through the AV node and lengthens its refractory period. Because the AV node is inhibited while the accessory pathway remains unaffected, impulses are more likely to travel via the accessory pathway relative to the AV node. This can increase conduction down the accessory pathway, especially during rapid atrial rhythms, and can lead to dangerously high ventricular rates or even malignant arrhythmias. So, verapamil may increase conduction through the accessory pathways rather than reliably preventing tachyarrhythmias. It does not slow conduction uniformly across the heart, and it does have a significant effect on AV nodal conduction.