Inert characteristic and functional refractory period of the atrioventricular node in rabbit heart preparation.

The effect of heart rate on the functional refractory period (FRP) of the atrioventricular node (AVN) is studied. A conclusion is reached that FRP, being a complex characteristic of AVN, should not be directly related to conduction time, but it can serve as a measure of the maximum moment acceleration which AVN is capable of transmitting to the lower-lying structures. It is proposed to use the coefficient of relative acceleration for quantitative estimation of the inert (dynamic) properties of the node at different heart rates. It is concluded that for a longer basic cycle length (BCL) AVN is characterized by greater reserve possibilities for transformation of accelerations of the input rhythm.