Abildskov J A, Lux R L
Nora Eccles Harrison Cardiovascular Research and Training Institute and the Division of Cardiology, University of Utah, Salt Lake City 84112, USA.
J Electrocardiol. 1997 Oct;30(4):307-13. doi: 10.1016/s0022-0736(97)80043-x.
Effects of heart rate on refractory period (RP) duration and disparity have opposing actions on vulnerability to fibrillation. Both bradycardia and tachycardia have been reported to increase vulnerability to fibrillation, and the role of their effects on RP duration and disparity in producing that effect is uncertain. That role has been investigated with a computer model of propagated excitation having nonuniform, cycle length-dependent refractoriness and slow propagation during incomplete recovery of excitability. Vulnerability was assessed as fibrillation threshold (FT), defined as the duration of train stimulation required to initiate simulated fibrillation. When measured as a function of train onset time during a cycle, FT initially decreased to a minimum and then increased to the original level. Slower rates shifted that curve upward and to the right, so that the FT was higher during early portions of the cycle but lower in later portions. Longer mean duration of RPs increased FT during all portions of the cycle, increased the difference of FT at various rates during early portions of the cycle, and decreased differences later in the cycle. Greater RP range reduced the FT and decreased the difference of FT with varied rate in early portions of the cycle, while increasing the difference in later portions. Accelerating rate had additional effects on FT-related to nonuniform propagation of responses prior to train stimulation. The findings defined mechanisms based on established effects of rate on RP, by which either tachycardia or bradycardia could increase vulnerability to fibrillation, and demonstrated the effects of RP range and duration on the mechanisms.
心率对不应期（RP）时长及差异的影响，在对颤动易感性方面有着相反的作用。据报道，心动过缓和心动过速都会增加颤动易感性，而它们对RP时长及差异产生该效应的作用尚不确定。利用一个具有非均匀、周期长度依赖性不应期以及兴奋不完全恢复期间缓慢传导的传播性兴奋计算机模型，对该作用进行了研究。将颤动阈值（FT）作为易感性的评估指标，颤动阈值定义为引发模拟颤动所需的串刺激时长。当作为一个周期内串刺激起始时间的函数进行测量时，FT最初会降至最低，然后又升至原始水平。较慢的心率会使该曲线向上并向右移动，这样在周期的早期部分FT较高，而在后期部分较低。较长的RP平均时长会使整个周期各部分的FT增加，使周期早期部分不同心率下的FT差值增大，而使周期后期的差值减小。更大的RP范围会降低FT，并减小周期早期部分不同心率下的FT差值，同时增大后期部分的差值。加速心率对FT还有额外影响，这与串刺激前反应的非均匀传导有关。这些发现基于心率对RP的既定影响确定了相关机制，据此心动过速或心动过缓都可能增加颤动易感性，并证明了RP范围和时长对这些机制的影响。
