Ring M E, Huang S K, Gorman G, Graham A R
Department of Internal Medicine, Tucson Veterans Administration Medical Center, Arizona.
Pacing Clin Electrophysiol. 1989 Sep;12(9):1502-13. doi: 10.1111/j.1540-8159.1989.tb06155.x.
Recently, radiofrequency (RF) energy has been used as an alternative energy source to direct-current (DC) electricity for catheter ablation of recurrent tachyarrhythmias. Since delivered energy is inversely related to impedance, factors that cause impedance rise during catheter ablation impede the ability to ablate tissue. To elucidate some of the factors responsible for impedance rise during RF (750 kHz) catheter ablation using a constant voltage RF generator, the effects of the following variables on impedance were studied in an in vitro bovine heart model: power setting (10-70 W), pulse duration (10-60 sec), catheter contact pressure (5-120 gm), repeated applications (2-4), and immersion media (saline vs citrated blood). Baseline impedance in blood was twice that of saline (190 vs 80 ohm) and rises in impedances occurred more rapidly in blood for the same energy settings. Increased power settings (greater than or equal to 30 W) and pulse duration (greater than or equal to 30 sec at 20 W) were associated with impedance rises in blood medium. Typically, impedance rises in blood were associated with blood coagulum on the catheter electrodes. Impedance rises in both saline and blood media were also associated with tissue charring and endocardial surface disruption. Once a rise in impedance occurred at the ablation site, repeated applications to the same site resulted in a more rapid rise in impedance. Catheter contact pressure of 80 gm or more also resulted in rapid impedance rise. These data suggest that factors other than set power and duration may also contribute to impedance rises during RF ablation. These findings may have important clinical implications in performing catheter ablation with RF energy.
最近，射频（RF）能量已被用作替代直流（DC）电的能源，用于复发性快速心律失常的导管消融。由于输送的能量与阻抗成反比，因此在导管消融过程中导致阻抗升高的因素会阻碍组织消融的能力。为了阐明使用恒压射频发生器在射频（750 kHz）导管消融过程中导致阻抗升高的一些因素，在体外牛心模型中研究了以下变量对阻抗的影响：功率设置（10 - 70 W）、脉冲持续时间（10 - 60秒）、导管接触压力（5 - 120克）、重复应用（2 - 4次）以及浸泡介质（盐水与枸橼酸盐血）。血液中的基线阻抗是盐水的两倍（190对80欧姆），并且在相同能量设置下，血液中的阻抗升高更快。功率设置增加（大于或等于30 W）和脉冲持续时间增加（在20 W时大于或等于30秒）与血液介质中的阻抗升高有关。通常，血液中的阻抗升高与导管电极上的血凝块有关。盐水和血液介质中的阻抗升高也与组织炭化和心内膜表面破坏有关。一旦在消融部位出现阻抗升高，对同一部位重复应用会导致阻抗更快升高。80克或更高的导管接触压力也会导致阻抗快速升高。这些数据表明，除了设定的功率和持续时间外，其他因素也可能导致射频消融过程中的阻抗升高。这些发现可能对使用射频能量进行导管消融具有重要的临床意义。
