Abstract：
Recently, polarity-dependent shock failures were reported in implantable cardioverter-defibrillators caused by structural failure in the high-voltage feedthrough. Short circuits may occur when the right ventricular coil is cathodal for phase 1 of biphasic shocks (cathodal shock). This viewpoint proposes a mechanism for observed polarity dependence and considers whether the same mechanism may apply in other shock-induced, short circuits. Implantable cardioverter-defibrillator connections to the lead traverse feedthroughs into the hermetically sealed housing (\"Can\"). The feedthrough comprises 2 concentric, conducting metal cylinders, the inner pin-conductor to the right ventricular coil and outer Can, separated by impermeable insulation. Shock failure depends on 3 conditions: 1) development of a fluid layer in the feedthrough, creating a conduction path in parallel with the shock pathway; 2) the radial gradient of the electric field in the fluid, so resistive heating during a shock vaporizes water to form a high-resistance gas bubble around the pin; and 3) field emission of electrons at the cathode, with rate and energy dependent on the field\'s strength and the cathode\'s potential-energy barrier to emission. For cathodal shocks, electrons emitted at the metal pin may initiate an ionization avalanche in the gas until it \"breaks down\" into a low-resistance plasma, resulting in a short circuit. For anodal shocks, the effective cathode is the liquid-gas interface, where the field is weaker than at the pin. Additionally, solvated electrons in aqueous solution must overcome a higher potential-energy barrier to be emitted. This permits the high-resistance gas bubble to stabilize so that the shock is completed.
摘要：
最近,据报道，植入式心脏复律除颤器中的极性依赖性电击失败是由高压馈通的结构故障引起的。当右心室线圈在双相电击（阴极电击）的1阶段处于阴极状态时，可能会发生短路。这种观点提出了一种观察到的极性依赖性的机制，并考虑了相同的机制是否可能适用于其他冲击引起的，短路。植入式心律转复除颤器与导线的连接穿过馈通进入密封外壳(“Can”)。馈通包括2个同心，导电金属圆筒，右心室线圈和外部Can的内部引脚导体，由不透水的绝缘隔开。冲击失效取决于3个条件：1）馈通中流体层的发展，创建与冲击路径平行的传导路径；2）流体中电场的径向梯度，因此，冲击过程中的电阻加热使水蒸发，在引脚周围形成高电阻气泡；3）阴极处电子的场发射，速率和能量取决于场的强度和阴极的势能势垒发射。对于阴极冲击，在金属引脚处发射的电子可能会在气体中引发电离雪崩，直到它“分解”为低电阻等离子体，导致短路。对于阳极电击，有效的阴极是液-气界面，其中磁场比引脚处弱。此外,水溶液中的溶剂化电子必须克服更高的势能势垒才能发射。这允许高阻力气泡稳定,从而完成冲击。
