Mouchawar G A, Wolsleger W K, Doan P D, Causey J D, Kroll M W
Pacesetter, Inc., Sylmar, California 91392-9221, USA.
Pacing Clin Electrophysiol. 1997 Jan;20(1 Pt 2):163-7. doi: 10.1111/j.1540-8159.1997.tb04835.x.
Pectorally implanted ICDs that defibrillate with the RV electrode and the ICD housing have gained clinical acceptance. However, it is still debatable whether adding an SVC electrode connected to the housing will further reduce the threshold of defibrillation (DFT). This study utilized eight pigs. DFTs were measured with a 50 V step-down protocol starting at 650 V (20 J). Shock strength for 50% success (E50) was estimated with the average of three reversals. In addition to alpha dummy device, Lead I (Pacesetter Models 1558 and 1538) or Lead II (Endotak 72) were used. Leads I are active fixation, true bipolar sensing with 5-cm shocking coils. Lead II has an integrated bipolar sensing with a 4.7-cm RV and 6.9-cm SVC shocking coils. A 95 microF defibrillation system was used to deliver a 44% tilt tuned biphasic 1.6/2.5 ms waveform, and to measure lead impedance. The RV electrode was the anode during phase I. With Lead IRV-->CAN the DFT was 531 +/- 75 V (13.6 +/- 3.8J) and the E50 was 496 +/- 89 (12 +/- 4.3 J). These were not significantly (NS) different than the DFT for RV-->CAN and SVC which was 518 +/- 84 V (13 +/- 4.2 J) or the E50 which was 476 +/- 84 V (11 +/- 3.9 J). Similar results were obtained with Lead II. Despite a decrease in lead impedance there was no apparent benefit from the addition of the SVC electrode. Lead I provided equivalent DFT performance to Lead II.
通过右心室（RV）电极和植入式心律转复除颤器（ICD）外壳进行除颤的胸壁植入式ICD已获得临床认可。然而，连接到外壳的上腔静脉（SVC）电极是否会进一步降低除颤阈值（DFT）仍存在争议。本研究使用了八头猪。采用从650V（20J）开始的50V递减方案测量DFT。通过三次反转的平均值估计50%成功率（E50）时的电击强度。除了α模拟装置外，还使用了I导联（Pacesetter型号1558和1538）或II导联（Endotak 72）。I导联为主动固定，真正的双极感知，带有5厘米的电击线圈。II导联具有集成的双极感知，带有4.7厘米的右心室和6.9厘米的上腔静脉电击线圈。使用95微法的除颤系统输送44%倾斜调谐的双相1.6/2.5毫秒波形，并测量导联阻抗。在第一阶段，右心室电极是阳极。对于I导联右心室→外壳，DFT为531±75V（13.6±3.8J），E50为496±89（12±4.3J）。这些与右心室→外壳和上腔静脉的DFT（518±84V，13±4.2J）或E50（476±84V，11±3.9J）相比无显著差异。使用II导联也获得了类似结果。尽管导联阻抗有所降低，但添加SVC电极并没有明显益处。I导联与II导联提供了相当的DFT性能。
