Johnson E E, Alferness C A, Wolf P D, Smith W M, Ideker R E
Department of Medicine, Duke University Medical Center, Durham, N.C.
Circulation. 1992 Jun;85(6):2267-74. doi: 10.1161/01.cir.85.6.2267.
Two sequential biphasic shocks delivered over separate lead configurations markedly improve defibrillation efficacy compared with a single shock alone. We investigated the effect of varying the intershock interval between sequential biphasic shocks on defibrillation.
Defibrillation thresholds (DFTs) were obtained in six dogs for shock separations ranging from 0.2 to 125 msec. The first shock was given from a catheter electrode in the right ventricular apex to a patch on the left lateral thorax; the second was from a small patch on the left ventricular apex to a catheter electrode in the right ventricular outflow tract. When the interval between shocks was less than or equal to 10 msec or greater than or equal to 75 and less than or equal to 125 msec, the mean DFTs were less than that previously found for the first shock by itself (4.2 versus 7.4 J, p = 0.002). At a separation of 50 msec, however, there was a marked rise in the DFT to 27 J. The mean DFT for the second shock at a delay of 50 msec was not different from the mean DFT previously found for the second shock by itself (7.2 versus 7.0 J). These results were confirmed in another six dogs using defibrillation probability-of-success curves. In 12 other dogs, probability-of-success curves were generated for delays between shocks as a percentage of the activation interval during ventricular fibrillation. Minimum defibrillation energy requirements were at two separations, 0.2 msec and 90% of the activation interval.
The optimal intershock interval between two sequential biphasic shocks is either less than or equal to 10 msec or greater than or equal to 75 and less than or equal to 125 msec. The marked rise in the DFT at a shock separation of 50 msec, requiring more energy than that for the first shock alone, suggests that the second shock at this time delay is likely to reinduce fibrillation after it is halted by the first shock until the second shock is strong enough to defibrillate independently of the first shock.
与单次电击相比，通过不同的导联配置依次给予两次双相电击可显著提高除颤效果。我们研究了依次给予的双相电击之间不同的电击间隔对除颤的影响。
在6只犬中获取了电击间隔从0.2至125毫秒时的除颤阈值（DFT）。第一次电击从右心室心尖的导管电极施加至左侧胸壁的贴片；第二次电击从左心室心尖的小贴片施加至右心室流出道的导管电极。当电击间隔小于或等于10毫秒或大于或等于75且小于或等于125毫秒时，平均DFT低于之前单独第一次电击时测得的值（4.2焦耳对7.4焦耳，p = 0.002）。然而，在间隔为50毫秒时，DFT显著升高至27焦耳。延迟50毫秒时第二次电击的平均DFT与之前单独第二次电击时测得的平均DFT无差异（7.2焦耳对7.0焦耳）。使用除颤成功概率曲线在另外6只犬中证实了这些结果。在另外12只犬中，绘制了电击延迟作为心室颤动期间激活间隔百分比的成功概率曲线。最低除颤能量需求出现在两个间隔时，即0.2毫秒和激活间隔的90%。
两次依次给予的双相电击之间的最佳电击间隔为小于或等于10毫秒或大于或等于75且小于或等于125毫秒。在电击间隔为50毫秒时DFT显著升高，需要比单独第一次电击更多的能量，这表明在此延迟下的第二次电击在被第一次电击终止颤动后可能会再次诱发颤动，直到第二次电击足够强以独立于第一次电击进行除颤。
