Flaker G, Schuder J, McDaniel W
University of Missouri-Columbia 65212.
Pacing Clin Electrophysiol. 1990 Dec;13(12 Pt 1):1580-4. doi: 10.1111/j.1540-8159.1990.tb06857.x.
To determine if multiple shocks adversely affect the success of later shocks compared with early shocks, we analyzed the success rates of initial shocks (defibrillation attempts 1-5), first half shocks (defibrillation attempts 1-20) and second half shocks (defibrillation attempts 21-40) in a canine model. Epicardial patches were placed on the right and left ventricle in 28 dogs. Ventricular fibrillation was induced by a 60-Hz shock. After 30 seconds, defibrillation was attempted using 7, 12, 13, or 18 joules with either a uniphasic or biphasic rectangular waveform. The uniphasic waveform was 5 msec in duration; the biphasic waveform was 10 msec, with the lagging 5-msec pulse one-half the amplitude of the leading 5-msec pulse. For uniphasic shocks, the right ventricular patch was positive; for biphasic shocks, the right ventricular patch was positive during the leading 5 msec of the shock and negative during the lagging milliseconds. A total of 960 fibrillation episodes were evaluated; no dog was involved in more than 40 fibrillation episodes. The success rates of defibrillation attempts 1-5, defibrillation attempts 1-20, and defibrillation attempts 21-40 were similar at 12, 13, and 18 joules. This information supports the continued use of up to 40 fibrillation trials in canine cardiac defibrillation. However, at 7 joules defibrillation attempts 21-40 were more successful than defibrillation attempts 1-5, and 1-20. With our methodology, these data are consistent with the hypothesis that low energy shocks create a "sensitizing" effect on cardiac tissue, allowing more successful defibrillation with repeated shocks.
为了确定与早期电击相比，多次电击是否会对后续电击的成功率产生不利影响，我们在犬类模型中分析了初始电击（第1 - 5次除颤尝试）、前半程电击（第1 - 20次除颤尝试）和后半程电击（第21 - 40次除颤尝试）的成功率。在28只犬的左右心室放置心外膜贴片。通过60赫兹电击诱发心室颤动。30秒后，使用7、12、13或18焦耳的单相或双相矩形波形进行除颤尝试。单相波形持续时间为5毫秒；双相波形持续时间为10毫秒，滞后的5毫秒脉冲幅度是领先的5毫秒脉冲的一半。对于单相电击，右心室贴片为正极；对于双相电击，在电击的前5毫秒内右心室贴片为正极，在滞后的几毫秒内为负极。共评估了960次颤动发作；没有一只犬参与超过40次颤动发作。在12、13和18焦耳时，第1 - 5次除颤尝试、第1 - 20次除颤尝试和第21 - 40次除颤尝试的成功率相似。这一信息支持在犬类心脏除颤中继续使用多达40次颤动试验。然而，在7焦耳时，第21 - 40次除颤尝试比第1 - 5次以及第1 - 20次除颤尝试更成功。根据我们的方法，这些数据与低能量电击对心脏组织产生“致敏”作用的假设一致，即重复电击可使除颤更成功。
