Which combination best describes the fast pathway's conduction and repolarization characteristics?

• A. Fast conduction and slow repolarization
• B. Slow conduction and fast repolarization
• C. Fast conduction and fast repolarization
• D. Slow conduction and slow repolarization

Answer: (A)

When thinking about two AV nodal pathways, the key is that conduction speed and recovery time are set independently. The fast pathway carries impulses quickly, but it has a longer recovery period after activation, meaning repolarization takes longer and it remains refractory for a longer time. The slow pathway, in contrast, conducts more sluggishly but recovers more quickly.

So the combination that fits the fast pathway is fast conduction with slow repolarization. This pairing—rapid impulse propagation coupled with a longer refractory period—explains why the fast pathway can conduct swiftly when ready, yet cannot be reactivated immediately after a beat. It also helps account for reentry dynamics in situations where the slow pathway can still conduct while the fast pathway remains refractory.