Fenelon Guilherme, Pereira Kleber Ponzi, de Paola Angelo A V
Department of Cardiology, Paulista School of Medicine, Federal University of São Paulo, São Paulo, SP, Brazil.
J Interv Card Electrophysiol. 2006 Jan;15(1):57-63. doi: 10.1007/s10840-006-7620-0.
We evaluated the factors affecting epicardial radiofrequency (RF) lesion formation in normal ventricular myocardium. In 16 dogs, a minithoracotomy was made and a sheath was placed in the pericardial space. Standard ablation lesions (4-mm tip catheter; 70 ( composite function) C/60 seconds) were created in each ventricle under fluoroscopy guidance (n = 7) or hand-held with direct visualization of the catheter to assure optimal electrode-tissue contact (n = 6). In the latter, thermally-shielded (TS) electrodes (50% tip surface along its 4 mm length) were used in 3/6 dogs. Catheter tip (4 mm) irrigation (13 mL/minutes; 40 ( composite function) C/60 seconds) was employed with conventional techniques in 3 additional dogs.
With optimal electrode-tissue contact (11 lesions), power (3.4 +/- 2.3 W vs. 16 +/- 13 W; p < 0.001) and pacing thresholds (0.2 +/- 0.0 mA vs. 3.6 +/- 5.7 mA; p = 0.004) were lower than standard RF (25 lesions). However, lesion dimensions were similar and transmural lesions did not occur (depth 2.8 +/- 1.1 mm vs. 3.0 +/- 1.5 mm). Catheter irrigation allowed high power outputs (43 +/- 6.1 W; p < 0.001) generating transmural lesions, 5/9 (55%), depth 6.4 +/- 2.1 mm. At constant power (2 W), catheter-tip temperature (52 +/- 5.2( composite function) C vs. 57 +/- 6.6( composite function) C; p = NS) and lesion (10 in each group) dimensions were similar for conventional and TS electrodes, but damage to parietal pericardium and lungs occurred with conventional electrodes only (70% vs. 0% p = 0.02).
Standard epicardial RF ablation does not produce deep lesions and exhibits a significant energy loss probably due to poor electrode-tissue contact. Catheter irrigation allows delivery of high power outputs to the epicardium consistently creating deeper lesions than standard ablation. TS electrodes may reduce damage to neighboring structures during epicardial RF ablation.
我们评估了影响正常心室心肌心外膜射频（RF）损伤形成的因素。对16只犬进行小开胸手术，并在心包腔内放置鞘管。在透视引导下（n = 7）或手持导管直接观察以确保电极与组织最佳接触的情况下（n = 6），在每个心室中创建标准消融损伤（4毫米尖端导管；70（复合功能）℃/60秒）。在后者中，3/6只犬使用了热屏蔽（TS）电极（沿其4毫米长度的尖端表面的50%）。另外3只犬采用传统技术进行导管尖端（4毫米）冲洗（13毫升/分钟；40（复合功能）℃/60秒）。
在电极与组织最佳接触的情况下（11个损伤），功率（3.4±2.3瓦对16±13瓦；p<0.001）和起搏阈值（0.2±0.0毫安对3.6±5.7毫安；p = 0.004）低于标准射频（25个损伤）。然而，损伤尺寸相似，且未出现透壁损伤（深度2.8±1.1毫米对3.0±1.5毫米）。导管冲洗可实现高功率输出（43±6.1瓦；p<0.001），产生透壁损伤，5/9（55%），深度6.4±2.1毫米。在恒定功率（2瓦）下，传统电极和TS电极的导管尖端温度（52±5.2（复合功能）℃对57±6.6（复合功能）℃；p = 无显著性差异）和损伤（每组10个）尺寸相似，但仅传统电极会对壁层心包和肺造成损伤（70%对0%，p = 0.02）。
标准的心外膜射频消融不会产生深部损伤，且可能由于电极与组织接触不良而存在明显的能量损失。导管冲洗可将高功率输出传递至心外膜，始终产生比标准消融更深的损伤。TS电极可能会减少心外膜射频消融过程中对邻近结构的损伤。
