Blanchard S M, Ideker R E
Department of Biomedical Engineering, Duke University, Durham, NC.
Am Heart J. 1994 Apr;127(4 Pt 2):970-7. doi: 10.1016/0002-8703(94)90075-2.
Six possible explanations for why some biphasic waveforms have lower defibrillation thresholds than monophasic waveforms of the same duration are as follows: (1) the impedance for the second phase of the biphasic shock is very low because electrode polarization develops during the first phase; (2) the large change in voltage between the first and second phases of a biphasic waveform is responsible for the increased defibrillation efficacy; (3) biphasic waveforms cause less severe detrimental effects in regions of high potential gradient; (4) the first phase of the biphasic waveform restores activity of the sodium channels, which makes defibrillation easier for the second phase; (5) the potential gradient required for defibrillation is less for biphasic waveforms than for monophasic waveforms; and (6) biphasic waveforms are better able to stimulate the myocardium to induce new action potentials or to cause refractory period prolongation. Evidence shows that, while a few of these proposed mechanisms are incorrect, several of the others may together contribute to the general superiority of biphasic waveforms.
对于为何某些双相波在除颤阈值方面低于相同持续时间的单相波，有六种可能的解释如下：（1）双相电击第二阶段的阻抗非常低，因为在第一阶段会发生电极极化；（2）双相波第一阶段和第二阶段之间的电压大幅变化导致除颤效果增强；（3）双相波在高电位梯度区域产生的有害影响较小；（4）双相波的第一阶段恢复钠通道的活性，这使得第二阶段更容易进行除颤；（5）双相波除颤所需的电位梯度比单相波小；（6）双相波更能刺激心肌诱导新的动作电位或导致不应期延长。有证据表明，虽然这些提出的机制中有一些是错误的，但其他一些机制可能共同促成了双相波的总体优势。
