Differential developmental effects of acute hypoxia on the rabbit atrioventricular conduction axis

The differential developmental effects of hypoxia on antegrade fast and slow and retrograde conduction through the atrioventricular junction are unknown. This study describes the effects of hypoxia on fast and slow antegrade atrioventricular node, infra-Hisian and retrograde conduction in immature and mature hearts during premature pacing protocols in excise, perfused adult and neonatal rabbits. The results are: (1) antegrade conduction delay through the atrioventricular node is the same developmentally, but delay through the His-Purkinje system is greater in adults; (2) hypoxia reduces the extra delay in the His-Purkinje system in adults; (3) fast atrioventricular node conduction is more sensitive to hypoxia in neonates than in adults, and slow atrioventricular node conduction is more sensitive to hypoxia in adults than in neonates, and (4) retrograde atrioventricular node conduction is more resistant to hypoxia in neonates than in adults.