| 1. BackgroundRadiofrequency catheter ablation ( RFCA )is an effective treatment of a variety of arrhythmia. Idiopathic ventricular tachycardia (IVT) is one of the most popular VT. In the past few years, the RFCA of VT from the left ventricular outflow tract has been made a new progress. Several studies found that IVT of LVOT was originated from the tissues above or below the aorta valve, especially around the opening of the left main coronary artery(LMCA). This area is very close to the origin of LMCA and aortic valve. Left main coronary artery occlusion has assocaited with RF ablation of LVOT tachycardia. This can be caused by extrinsic compression of the vessel, intraluminal thrombosis, intimal dissection, or coronary artery vasospasm. Perforation and prolapse of the aortic or mitral valves also can occur. Temperature controlled RFCA maybe reduced the occurance of complications. But the pathological effects of radiofrequency4energy application in aorta is still unknown . So this study was to investigate:ヾynamic pathological process after temperature controlled RFCA in the aorta root in rabbits, ヽorrelation between the degree of the injury caused by RF enery and temperature or time d) possibility of the animal model which is use for interventive experiment without radiative machine.2. material and methods:? Dynamic Observation Group:The rabbits were anesthetized with thiopental . Then the breast bone was incised along the middle line to expose the mediastina. The pericardium was sheared , and a incision was made in left ventricular wall. The RF catheter was lead into the left ventricle through the section, and put into the aorta root. RF energy was applied in the region (60S *60癈).After the ablation, the incision was sutured. Animals were euthanized at 30mins, 12hrs, 24hrs, 48hrs, 7days and 30days after ablation. The tissue of the aorta were stained with hematoxylin and eosin, and the slides were viewed in light microscopy. ?Instant Injury Group:The operation procedure was almost same with dynamic observation group. There were three levels in temperature(50癈\ 60癈\ 70癈) and two levels in time( 30s and 60s). After ablation, the tissue of aorta and heart were taken down immediately. The slides were stained with hematoxylin and eosin. The value of the lesion depth would be measured in the light microscopy. Correlation betweent lesion depth and temperature or time were analyzed with factorial analysis of variace., with PO.05 considered significant.3. Result? Normal structure of aorta root of rabbits:There are three levels in the rabbits aorta root: tunica intima, tunica media and tunica adventitia. The intima is very thin, and the surface is covered by a layer of endothelial cells. The sub-intima is composed by loose connective tissues. Thirty to fifty layers of elastic membrane can be found in the tunica media. The smooth muscles are visible among the elastic membrane. The structure of adventitia is simple, and transited to the peripheral connective tissue.Sometimes the remains of the valve ring can be seen.? Dynamic Observation Group:At SOminutes, the endothelium was disappeared and the degeneration of the cells could be found. At 12hrs, coagulation necrosis of the cells appeared in the lesion, but the elastic membrane still kept intact. At 24hrs, more typical coagulation necrosis were seen, and acute inflammation was obvious. At 48hrs, a thrombus was found to attached to the lesion of aorta wall. At 7days, endothelium was recovered and fibroblasts were viewed in the margin of the lesion. At SOdays: multiple calcification nodules were visible in the lesion, one of them was in the region of aortic valve.? Instant Injury Group:The result of statistical analysis is demonstrated that there is a significant correlation between the depth of RF lesion and the temperature or the depth and the time(P<0.05). If the time of RF energy application is same, there is a relationship of direct ratio between interface temperature and depth of the RF lesion. |
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