Friedman P A, Foley D A, Christian T F, Stanton M S
Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN 55905, USA.
Pacing Clin Electrophysiol. 1998 Feb;21(2):339-51. doi: 10.1111/j.1540-8159.1998.tb00058.x.
Most patients with implantable defibrillators have diminished cardiac function. Progressive heart failure might impair defibrillation efficacy, leading to interpreted device failure. This study sought to determine the effect of ventricular dysfunction on defibrillation energy using a biphasic endocardial system. Eleven dogs were ventricularly paced at 225 pulses/min for 2 weeks to induce ventricular dysfunction, and five control dogs remained unpaced. Dose response defibrillation probability curves were generated for each animal at baseline, after 2 weeks (at which time the pacemakers were turned off in the paced group), and then 1 week later. The defibrillation thresholds, ED20, ED50, and ED80 (the 20%, 50%, and 80% effective defibrillation energies, respectively) were determined for each dog at each study. In the paced dogs, the mean ejection fraction fell from 55% to 25% after pacing (P < 0.0001), and rose to 46% after its discontinuation (P = 0.0002). The defibrillation threshold, ED20, ED50, and ED80 remained unchanged in both the control and paced groups for all three studies, even after adjustment for dog weight or left ventricular mass. Rapid pacing produced no change in left ventricular mass. It induced ventricular cavity dilatation and wall thinning, which had opposing effects on defibrillation energy requirements, resulting in no net change of the ED50 in heart failure. In conclusion, the defibrillation efficacy of a biphasic transvenous system is not changed by the development of heart failure using the rapid paced canine model.
大多数植入式除颤器患者的心功能会减弱。进行性心力衰竭可能会损害除颤效果，导致被解读为设备故障。本研究旨在使用双相心内膜系统确定心室功能障碍对除颤能量的影响。11只犬以每分钟225次脉冲进行心室起搏，持续2周以诱发心室功能障碍，5只对照犬未进行起搏。在基线、2周后（此时起搏组的起搏器关闭）以及1周后，为每只动物生成剂量反应除颤概率曲线。在每次研究中，为每只犬确定除颤阈值、ED20、ED50和ED80（分别为20%、50%和80%有效除颤能量）。在起搏的犬中，起搏后平均射血分数从55%降至25%（P<0.0001），停止起搏后升至46%（P = 0.0002）。在所有三项研究中，对照组和起搏组的除颤阈值、ED20、ED50和ED80均保持不变，即使在对犬体重或左心室质量进行调整后也是如此。快速起搏未导致左心室质量发生变化。它导致心室腔扩张和室壁变薄，这对除颤能量需求产生相反的影响，导致心力衰竭时ED50无净变化。总之，使用快速起搏犬模型，心力衰竭的发展不会改变双相经静脉系统的除颤效果。
