射频消融离体心肌及热场分布的实验研究

Radiofrequency Ablation of Myocardium In Vitro and Thermal Field Distribution

【目的】体外实验探索使用Cool-tipTM射频消融电极进行离体心肌组织射频消融的适宜条件,以及消融灶范围内温度变化趋势,为制定解除梗阻性肥厚型心肌病(HOCM)左心室流出道梗阻,提供安全可靠的射频消融条件参考。【方法】采用针尖裸露端2 cm的Cool-tipTM射频消融电极对30枚新鲜离体猪心进行射频消融,能量输出功率分别采用20、30、40、60和80W,消融时间为2 min、4 min,观察不同消融条件造成的心肌组织凝固范围和形态。采用实时温度测量设备测量消融电极针尖处及距其5 mm、10 mm的热场温度变化。【结果】单次能量输出造成的心肌消融灶范围为横径(0.8~2.3)cm×纵径(2.2~3.2)cm,横径变化范围更大;随输出功率及时间增加,心肌消融灶体积增大,为(0.8~8.1)cm3。消融过程中,各温度测量点温度均随时间增加而升高,针尖处温度迅速升高,最高温度可达(128.5±0.3)℃;距针尖5 mm处最高温度可达(98.1±0.4)℃,距针尖10 mm处最高温度可达(72.9±0.2)℃。【结论】对离体心肌射频消融可得到随时间、功率改变而变化的消融灶,以射频电极为中心的向外部温度逐渐降低的热场分布,为临床采用超声引导下经皮室间隔射频消融技术治疗梗阻性肥厚型心肌病的参数条件选择提供基本依据。

【Objectives】To explore the optimum criteria and temperature change trend of radiofrequency ablation(RFA)with Cool-tipTM electrode for the myocardial tissue in vitro,and to provide a safe and reliable reference for RFA therapy in obstruction relief of hypertrophic obstructive cardiomyopathy(HOCM).【Methods】Thirty pieces of fresh porcine hearts were treated by RFA under echocardiography-guided in vitro.The exposed tip of RFA needle of Cool-tipTM electrode was 2 cm.The output power was 20 W,30 W,40 W,60 W,and 80 W respectively,while the time spending of RFA was 2 min and 4 min.The three paralleled mocouple probes were inserted into myocardia at the place of electrode tip,5 mm from electrode tip,and 10 mm from electrode tip.The range of cardiac tissue coagulation and thermal field distribution were observed in different ablation parameters.【Results】Range of coagulation diameters for single outpower was transverse diameter(0.8~2.3)cm×vertical diameter(2.2~3.2)cm,and the change in the transverse diameter was larger.With the increase in outpower and time spending of ablation,the volume of the cardiac tissue coagulation was enlarged,which was(0.8~8.1)cm3.The temperature of each measuring point increased with the time rising dur-ing ablation.The temperature at the place of electrode tip rose rapidly,and the highest temperature was(128.5±0.3)℃;the highest temperature of 5 mm from electrode tip was(98.1±0.4)℃;and the highest temperature of 10 mm from electrode tip was(72.9±0.2)℃.【Conclusions】The RFA of myocardium in vitro could form focal necrosis lesion,which could change with different time duration and outpower.The thermal distribution showed gradually decrease from the internal to the external.This study provided a basis for condition selection in the treatment of HOCM by ultrasoundguided percutaneous ventricular septal radiofrequency ablation.