Billette J
Am J Physiol. 1987 Jan;252(1 Pt 2):H163-77. doi: 10.1152/ajpheart.1987.252.1.H163.
To study the intranodal origin of the functional properties of the atrioventricular node, progressive changes in nodal cell activation time and cycle length occurring during complete sequences of periodic premature stimulation of the atrium were determined for 419 nodal cells recorded in 11 isolated rabbit heart preparations. The conduction time in proximal nodal cells including the N cells increased only at very short coupling intervals. Conduction time in the distal node (NH and H cells) first increased and then decreased with increasing prematurity. The major fraction of the basic and premature delays developed between N and NH cell activation, a period devoid of upstrokes. The effective and functional refractory periods were related to the minimum intervals between successive upstrokes at the node entrance and outlet, respectively. These results suggest that the cycle-length dependency of nodal conduction is the result of complex changes in propagation time occurring at three levels in the node, whereas the effective and functional refractory periods reflect reactivation limits of cells located at the node entrance and outlet, respectively.
为研究房室结功能特性的结内起源，在11个离体兔心标本中记录了419个结细胞，测定了心房周期性早搏刺激完整序列期间结细胞激活时间和周期长度的渐进性变化。包括N细胞在内的近端结细胞的传导时间仅在非常短的耦联间期增加。远端结（NH和H细胞）的传导时间随早搏增加先增加后减少。基本延迟和早搏延迟的主要部分发生在N细胞和NH细胞激活之间，这一时期没有上升支。有效不应期和功能不应期分别与结入口和出口处连续上升支之间的最短间期有关。这些结果表明，结传导的周期长度依赖性是结内三个水平传播时间复杂变化的结果，而有效不应期和功能不应期分别反映了位于结入口和出口处细胞的再激活极限。
