Ruffy R, Imran M A, Santel D J, Wharton J M
University of Utah Health Sciences Center, Salt Lake City, USA.
J Cardiovasc Electrophysiol. 1995 Dec;6(12):1089-96. doi: 10.1111/j.1540-8167.1995.tb00386.x.
The delivery of radiofrequency (RF) energy through conventional catheter electrodes is often associated with coagulation necrosis at the tissue-electrode interface, with resultant impedance rise and limited lesion size. This study was performed to examine the effects of catheter tip cooling during RF delivery, to test the hypothesis that such cooling would decrease the likelihood if impedance rise and allow the creation of larger endomyocardial lesions.
The experiments were performed in eight open chest, anesthetized sheep. RF lesions were created within both ventricular chambers of each animal through a catheter tip that could be cooled with a saline perfusate. Assignment of cooled versus noncooled RF delivery to either ventricle was alternated from one animal to the next. In each set of experiments, lesion volumes relative to the mode of RF delivery were compared. The mean power delivered via the cooled electrode (22.04 +/- 4.51 W) was significantly higher than that delivered via the noncooled electrode (6.10 +/- 2.47 W; P < 0.001). The mean duration of RF delivery was 42.7 +/- 11.2 sec for noncooled lesions versus 49.2 +/- 6.8 sec for cooled lesions (P < 0.01). Mean lesion volume was 436.07 +/- 177.00 mm3 for noncooled RF delivery versus 1247.78 +/- 520.51 mm3 for cooled RF delivery (P < 0.001). This significantly larger lesion size with cooled RF delivery was associated with no instance of impedance rise in 27 attempts versus 11 impedance rises in 28 attempts with noncooled RF (P < 0.001).
Delivery of RF energy through a cooled catheter tip allows the creation of larger endomyocardial lesions by limiting the occurrence of impedance rise despite the delivery of greater energy. These observations suggest that, under certain conditions, resistive tissue heating at a distance from the site of current delivery may play an important role in RF ablation therapy.
通过传统导管电极输送射频（RF）能量通常会在组织 - 电极界面处导致凝固性坏死，从而导致阻抗升高和病变大小受限。本研究旨在检查在射频输送过程中导管尖端冷却的效果，以验证这样的冷却会降低阻抗升高的可能性并允许形成更大的心内膜病变这一假设。
实验在八只开胸、麻醉的绵羊身上进行。通过可由盐水灌注液冷却的导管尖端在每只动物的两个心室内制造射频病变。从一只动物到下一只动物，交替将冷却与未冷却的射频输送分配到任一心室。在每组实验中，比较相对于射频输送模式的病变体积。通过冷却电极输送的平均功率（22.04±4.51瓦）显著高于通过未冷却电极输送的功率（6.10±2.47瓦；P<0.001）。未冷却病变的射频输送平均持续时间为42.7±11.2秒，而冷却病变为49.2±6.8秒（P<0.01）。未冷却射频输送的平均病变体积为436.07±177.00立方毫米，而冷却射频输送为1247.78±520.51立方毫米（P<0.001）。冷却射频输送时这种显著更大的病变大小与27次尝试中无阻抗升高的情况相关，而未冷却射频在28次尝试中有11次阻抗升高（P<0.001）。
通过冷却的导管尖端输送射频能量可通过限制阻抗升高来形成更大的心内膜病变，尽管输送了更大的能量。这些观察结果表明，在某些条件下，远离电流输送部位的电阻性组织加热可能在射频消融治疗中起重要作用。
