Feedback mechanisms and dynamics of atrioventricular node propagation.
Feedback mechanisms and dynamics of atrioventricular node propagation.
复制标题
房室结传播的反馈机制和动力学。
DOI：
10.1111/j.1749-6632.1990.tb15076.x
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发表时间：
1990
影响因子：
5.2
通讯作者：
Levy,MN
中科院分区：
文献类型：
--
作者：
Cheng,J;Levy,MN
The atrioventricular (AV) node is a key element of the specialized conduction system of the heart. Normally, it is the sole egress for the propagation of atrial impulses to the ventricles. The AV node may be affected by a number of factors, such as cardiac cycle length, autonomic neural activity, and drugs. In this paper, however, we will consider only the effects of varying the cardiac cycle length on AV conduction. The conduction time (AV interval) of a cardiac impulse from atria to ventricles increases as the cardiac cycle length (AA interval) is diminished. I4 This effect becomes more pronounced the shorter the AA interval. Thus, the AV node constitutes a nonlinear system, because its response depends not only on the magnitude of the input change but also on the level of the input at which such a change is imposed. Another important characteristic of the AV conduction system is its dependence on the AV recovery time. 5-" The AV recovery time represents the time available for the AV node to recover before its next excitation. This time may be approximated by the VA interval, which is the time from the beginning of a given ventricular excitation (V) until the beginning of the next atrial excitation (A). The graph of the AV interval plotted as a function of the preceding VA interval has been referred to as the" AV recovery c~ rve.''~~~'~~~ Thus, the VA interval reflects the refractoriness of the AV node at the arrival time of the next atrial impulse. The shorter the AV recovery time, the more refractory may be the AV conduction system. A shortening of the VA interval may prolong the next AV interval, because the atrial impulse may reach the AV node earlier in the AV nodal refractory period.Moreover, a change in the AV interval has an inverse effect on the VA interval. By definition, the VA interval is the algebraic difference between the cardiac cycle length and the AV conduction time for any complete cardiac cycle. Consequently, positive feedback may prevail when the AA interval remains~ onstant.',~ For example, during atrial pacing at a constant AA interval, a perturbation that increases the AV interval
