Ellis J R, Martin D T, Venditti F J
Cardiac Electrophysiology Laboratory, Lahey Clinic Medical Center, Burlington, MA 01805.
Circulation. 1994 Oct;90(4):1820-5. doi: 10.1161/01.cir.90.4.1820.
Reduction in R-wave amplitude immediately after defibrillation shocks in an integrated shock/sense transvenous cardioverter-defibrillator (TCD) lead system has prompted concerns regarding adequate sensing after failed shocks. We therefore studied redetection characteristics for ventricular fibrillation after unsuccessful defibrillation shocks in a TCD system to determine if these observations have clinical relevance.
Fifty patients with this shock/sense TCD lead system underwent conversion testing of their TCD at several time intervals. There were a total of 142 failed shocks events recorded, including 10, 15, 70, and 47 events at implantation, predischarge, and 2- and 6-month testing, respectively. Initial detection time (IDT) and redetection time (RDT) for ventricular fibrillation were measured from event markers for all unsuccessful defibrillation shocks. To assess the effect of failed shocks on electrogram quality, 54 failed shock episodes were evaluated in 37 of the 50 patients by measuring electrograms during VF before and after shock. Mean RDT for the entire group was 5.3 +/- 3.5 seconds compared with an IDT of 4.5 +/- 3.3 seconds (P = NS). There were no significant differences between IDT and RDT at implantation or any follow-up testing period, despite a significant decline in R-wave amplitude from 8.1 +/- 3.5 to 6.8 +/- 2.8 mV (P < .0001) measured 3 to 6 seconds after shock delivery. Analysis of 8 individuals with any extended RDT (> or = 10 seconds) showed no significant differences in clinical or implantation characteristics when compared with 42 individuals without extended RDT.
In this integrated shock/sense TCD lead system, unsuccessful shock delivery has no significant effect on redetection of ventricular fibrillation at device implantation or up to 6 months of follow-up, despite an observed reduction in postshock R-wave amplitude. Therefore, the reported reduction in electrogram quality after a shock is of no practical importance because sensing of ventricular fibrillation does not appear to be compromised in this particular TCD system. Whether this applies to other implantable cardioverter-defibrillator pulse generators and lead systems with different sensing characteristics requires further evaluation.
在集成式电击/感知经静脉心脏转复除颤器（TCD）导联系统中，除颤电击后立即出现的R波振幅降低引发了对电击失败后感知是否充分的担忧。因此，我们研究了TCD系统中除颤电击失败后室颤的重新检测特征，以确定这些观察结果是否具有临床相关性。
50例使用这种电击/感知TCD导联系统的患者在多个时间间隔接受了TCD的转换测试。共记录到142次电击失败事件，其中分别在植入时、放电前以及2个月和6个月测试时发生的事件有10次、15次、70次和47次。对于所有除颤电击失败事件，从事件标记开始测量室颤的初始检测时间（IDT）和重新检测时间（RDT）。为评估电击失败对心电图质量的影响，在50例患者中的37例中对54次电击失败事件进行了评估，通过测量电击前后室颤期间的心电图。整个组的平均RDT为5.3±3.5秒，而IDT为4.5±3.3秒（P = 无显著差异）。在植入时或任何随访测试期间，IDT和RDT之间均无显著差异，尽管在电击后3至6秒测量的R波振幅从8.1±3.5 mV显著下降至6.8±2.8 mV（P <.0001）。对8例任何重新检测时间延长（≥10秒）的个体进行分析，与42例未出现重新检测时间延长的个体相比，在临床或植入特征方面无显著差异。
在这种集成式电击/感知TCD导联系统中，尽管观察到电击后R波振幅降低，但电击失败对设备植入时或长达6个月随访期间室颤的重新检测没有显著影响。因此，所报道的电击后心电图质量降低并无实际重要性，因为在这个特定的TCD系统中，室颤的感知似乎未受影响。这是否适用于其他具有不同感知特征的植入式心脏转复除颤器脉冲发生器和导联系统需要进一步评估。
