Developmental changes of atrioventricular nodal recovery properties

Atrioventricular (AV) nodal recovery properties can be studied by a periodic premature stimulation protocol performed at a slow basic rate. Developmental aspects of these properties have not been determined. The purpose of this study was to determine the developmental changes of AV nodal recovery properties. Forty-three children and young adults (male:female ratio 25:18) without AV nodal disease (aged 3.3 to 21.9 years) were studied by delivering premature atrial extrastimuli coupled to basic driven atrial beats. The individual recovery curve was tilted to the equation: A₂H₂ = Aorta + exp(α -H₁A₂/τ) for H₁A₂ ≤θ, where A₀H₀ is the minimum AH interval, H₁A₂ is any recovery interval that exceeds the nodal effective refractory period, A₂H₂ is the corresponding nodal conduction time at any given H₁A₂, α is a constant, τ is the recovery time constant, and θ is the nodal effective refractory period. We found that: (1) A₀H₀ and a constant did not change significantly with age, (2) both τ (r = 0.324; p <0.05) and θ (r = 0.401; p <0.05) had a positive correlation with age; and (3) the maximum change in A₂H₂ with a 10-ms decrement in H₁A₂ was 32 ms and did not change significantly with age. Our results suggest that AV nodal recovery properties are age-dependent and both the recovery time constant and effective refractory period lengthen with age.