Conduction disturbances caused by high current density electric fields.
Conduction disturbances caused by high current density electric fields.
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DOI：
10.1161/01.res.66.5.1190
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发表时间：
1990-05
影响因子：
20.1
通讯作者：
S. Yabe;William M. Smith;J. Daubert;P. Wolf;D. Rollins;R. Ideker
中科院分区：
文献类型：
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作者：
S. Yabe;William M. Smith;J. Daubert;P. Wolf;D. Rollins;R. Ideker
在内部除颤期间，除颤电极附近出现大于100 V/cm的电位梯度。这种强磁场可能会导致有害影响，包括心律失常。这项研究确定了1）这种强场对激活传播的影响，以及2）这些影响对于单相和双相电击是否不同。电击过程中的电压和电位梯度，以及电击前后的激动序列，从放置在6只犬右心室3 x 3 cm区域上的117个心外膜电极标测。从标测区域右侧的狭长电极以350 msec的周期长度进行起搏，以生成平行激动等时线。在最后一次起搏刺激后300 msec，通过标测区域左侧的网状电极作为阴极，以右心房为阳极，输送持续时间为10 msec的单相电击或两个相位持续时间为5 msec的双相电击。给出70-850 V的冲击，并且通过使用有限元法从测量的电势和纤维取向计算每个记录电极处的电势梯度和电流密度。电击后200 msec恢复起搏，并绘制激活序列长达5分钟。电位梯度范围为1 - 189 V/cm，标测区域左侧高场，右侧低场。在电位梯度较弱的地方，电击后的第一个激活序列与电击前相似，但激活被阻断，而没有传导到单相电击梯度大于64 +/- 4（平均值+/- SD）V/cm和双相电击梯度大于71 +/- 6 V/cm的区域。这些值存在显著差异（p <0.003）。电位梯度越高，传导恢复前阻滞持续时间越长。但是，在相同场强下，双相波形的阻滞持续时间通常短于单相波形。总之，传导阻滞可以跟随任一波形，但双相波形比单相波形引起更少的阻滞。这种效应可以部分解释双相电击除颤效果的增加。
During internal defibrillation, potential gradients greater than 100 V/cm occur near defibrillation electrodes. Such strong fields may cause deleterious effects, including arrhythmias. This study determined 1) the effects of such strong fields on the propagation of activation and 2) whether these effects were different for monophasic and biphasic shocks. Voltages and potential gradients during the shock, as well as activation sequences before and after the shock, were mapped from 117 epicardial electrodes placed over a 3 x 3-cm area on the right ventricle in six dogs. Pacing at a cycle length of 350 msec was given from a long narrow electrode on the right side of the mapped area to generate parallel activation isochrones. A monophasic shock, 10 msec in duration, or a biphasic shock with both phases 5 msec in duration was delivered 300 msec after the last paced stimulus via a mesh electrode on the left side of the mapped area as the cathode, with the anode on the right atrium. Shocks of 70-850 V were given, and the potential gradient and current density at each recording electrode were calculated from the measured potentials and fiber orientation by using a finite element method. Pacing was resumed 200 msec after the shock, and activation sequences were mapped for up to 5 minutes. Potential gradients ranged from 1 to 189 V/cm with high fields on the left side and low fields on the right side of the mapped area. Where the potential gradient was weak, the first activation sequence after the shock was similar to that before the shock, but activation blocked without conducting into areas where the gradient was greater than 64 +/- 4 (mean +/- SD) V/cm for monophasic and greater than 71 +/- 6 V/cm for biphasic shocks. These values are significantly different (p less than 0.003). The higher the potential gradient, the longer was the duration of block before conduction returned. Block duration, however, was generally shorter for biphasic than for monophasic waveforms of the same field strength. In conclusion, conduction block can follow either waveform, but biphasic waveforms cause less block than monophasic waveforms. This effect may partially explain the increased defibrillation efficacy of biphasic shocks.