Purkinje-mediated Effects in the Response of Quiescent Ventricles to Defibrillation Shocks
Purkinje-mediated Effects in the Response of Quiescent Ventricles to Defibrillation Shocks
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DOI：
10.1007/s10439-009-9829-4
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发表时间：
2010-02-01
影响因子：
3.8
通讯作者：
Vigmond, Edward J.
中科院分区：
文献类型：
--
作者：
Boyle, Patrick M.;Deo, Makarand;Vigmond, Edward J.
在正常的心脏功能中，浦肯野系统(PS)促进了心脏的有序激活，浦肯野系统是排列在脑室内的一个由快速传导纤维组成的专门网络。它在室性除颤中的作用尚不清楚。PS的物理特性使其不太适合使用现代实验技术进行直接电学观测。本研究使用计算机模拟的方法来评估PS对电刺激反应的贡献。模拟正常的窦性心律，心外膜穿透部位的分布与实验结果一致。对有无PS的静止室施加不同强度和方位的除颤电击，并分析电激活情况。所有的激波都在平行于电场的PS分支中引起局部极化，从而导致激励在整个网络中迅速传播。这在心肌部位产生了早期的激活，那里的组织不被电击所激发，并与PS相连。当PS存在时，沿心脏心尖-基底轴的电击导致激活时间的显著缩短；这些电击特别令人感兴趣，因为内部心律转复除颤器产生的磁场往往具有相同方向的强分量。PS诱导的改变的程度，无论是时间上还是空间上，都受到休克激活心肌数量的限制。增加场强减少了浦肯野-心肌交界处PS和心室组织之间的传输延迟，但这对器官水平的反应没有重大影响。较弱的电击直接影响较小的心肌组织，但容易刺激PS，这使得PS对远场兴奋的贡献比较强的电击更大。
In normal cardiac function, orderly activation of the heart is facilitated by the Purkinje system (PS), a specialized network of fast-conducting fibers that lines the ventricles. Its role during ventricular defibrillation remains unelucidated. Physical characteristics of the PS make it a poor candidate for direct electrical observation using contemporary experimental techniques. This study uses a computer modeling approach to assess contributions by the PS to the response to electrical stimulation. Normal sinus rhythm was simulated and epicardial breakthrough sites were distributed in a manner consistent with experimental results. Defibrillation shocks of several strengths and orientations were applied to quiescent ventricles, with and without PS, and electrical activation was analyzed. All shocks induced local polarizations in PS branches parallel to the field, which led to the rapid spread of excitation through the network. This produced early activations at myocardial sites where tissue was unexcited by the shock and coupled to the PS. Shocks along the apico-basal axis of the heart resulted in a significant abbreviation of activation time when the PS was present; these shocks are of particular interest because the fields generated by internal cardioverter defibrillators tend to have a strong component in the same direction. The extent of PS-induced changes, both temporal and spatial, was constrained by the amount of shock-activated myocardium. Increasing field strength decreased the transmission delay between PS and ventricular tissue at Purkinje-myocardial junctions (PMJs), but this did not have a major effect on the organ-level response. Weaker shocks directly affect a smaller volume of myocardial tissue but easily excite the PS, which makes the PS contribution to far field excitation more substantial than for stronger shocks.