Nath S, Whayne J G, Kaul S, Goodman N C, Jayaweera A R, Haines D E
Cardiovascular Division, University of Virginia School of Medicine, Charlottesville.
Circulation. 1994 Jun;89(6):2667-72. doi: 10.1161/01.cir.89.6.2667.
We postulated that the late electrophysiological effects of radiofrequency (RF) ablation may be related to microvascular injury extending beyond the region of acute coagulation necrosis.
Eighteen RF lesions created in the left anterior descending coronary artery (LAD) perfusion bed of seven open chest anesthetized dogs were studied. The ablation electrode and surrounding myocardium were imaged using high-resolution two-dimensional echocardiography at x 4 magnification. After 60 seconds of RF delivery, sonicated albumin microbubbles (mean size, 4.3 microns) were injected into the LAD to measure regional myocardial perfusion, and time-intensity plots were generated from simultaneously acquired two-dimensional echocardiography images. The regions with persistent contrast effect on two-dimensional echocardiography were larger than the pathological lesions (mean cross-sectional area, 48.3 +/- 6.3 versus 19.3 +/- 4.7 mm2, respectively; P < .0001). The mean contrast transit rate in the area corresponding to the pathological lesion was 25 +/- 12% of that in the normal myocardium, but it was also reduced beyond the lesion, being 48 +/- 27% and 82 +/- 28% of normal, respectively, in the 3-mm and 3- to 6-mm circumferential rims surrounding the pathological lesion (P < .05). Electron microscopy performed in two additional dogs with similar lesions demonstrated the presence of ultrastructural damage to the microvascular endothelium well beyond the pathological lesion edge.
RF catheter ablation not only results in a marked reduction in blood flow within the acute pathological lesion but also causes reduced flow beyond the borders of the acute lesion because of microvascular endothelial cell injury. The progression or resolution of tissue injury within the region beyond the border of the pathological lesion may explain the late electrophysiological effects of RF ablation.
我们推测，射频（RF）消融的晚期电生理效应可能与微血管损伤有关，这种损伤超出了急性凝固性坏死区域。
对7只开胸麻醉犬左前降支冠状动脉（LAD）灌注床内形成的18个RF损伤灶进行了研究。使用高分辨率二维超声心动图以4倍放大率对消融电极及周围心肌进行成像。在施加60秒RF后，将超声处理的白蛋白微泡（平均大小4.3微米）注入LAD以测量局部心肌灌注，并从同步采集的二维超声心动图图像生成时间-强度图。二维超声心动图上持续出现对比剂增强效应的区域大于病理损伤灶（平均横截面积分别为48.3±6.3与19.3±4.7平方毫米；P<0.0001）。对应于病理损伤灶区域的平均对比剂通过速率为正常心肌的25±12%，但在损伤灶以外区域也降低，在病理损伤灶周围3毫米和3至6毫米的圆周边缘分别为正常的48±27%和82±28%（P<0.05）。对另外两只具有类似损伤灶的犬进行的电子显微镜检查显示，微血管内皮的超微结构损伤远超出病理损伤灶边缘。
RF导管消融不仅导致急性病理损伤灶内血流显著减少，还因微血管内皮细胞损伤导致急性损伤灶边界以外区域血流减少。病理损伤灶边界以外区域组织损伤的进展或消退可能解释了RF消融的晚期电生理效应。
