Asked by Anonymous
AV node contains 2 pathways:
1. Alpha pathway (Slow):
- Slow conduction
- Short refractory period
2. Beta pathway (Fast):
- Fast conduction
- Long refractory period
Normal condition: Anterograde conduction occurs down the fast pathway
Atrial extrasystole:
- An extrasystole during the long refractory pathway of fast (beta) pathway propagates exclusively down the slow pathway
- By the time the impulse reaches down the distal end of fast pathway, it is no longer refractory and it conducts retrogradely
- A re-entrant circuit is formed:
- Anterograde conduction down the slow pathway
- Retrograde conduction up the fast pathway
- Almost simultaneous activation of atria and ventricles
