Introduction : The aim of this study is to obtain new insight into possible relation between functional properties of slow concealed pathway and rate-dependent properties of AV-node.

  Methods : Rate-dependent nodal properties of recovery, facilitation, and fatigue were characterized by stimulation protocols in one groups of (N=7) isolated superfused AV-Nodal rabbits. Small miniature lesions were made by delivering constant voltage (110 V-100 s) with unipolar silver electrode.

  Results : Fast pathway ablation significantly decreased facilitation and had no effect on fatigue and nodal refractoriness. The most important effect of fast pathway ablation was prolongation of minimum conduction time.

  Conclusion : The FP-ablation revealed the presence of the concealed SP. Rate-dependent property of node is dependent to dynamic interaction between concealed slow with slow pathway. Fast pathway involved in the mechanism of facilitation.