Aneurismas experimentales en ratas / Experimental aneurysms in rats

Objective. 1. The creation of an aneurysm model in an arterial bifurcation for microsurgical training in rats. 2. To verify angiographically the aneurysms patency performing endovascular maneuvers. Material and method. 10 Wistar rats weighted 400-600g were used. Ten aneurysms were performed, 9 in the final aortic bifurcation and one in the origin of the renal artery. The aneurismal sac derived from the external iliac vein. Angiography in each animal was done to examine aneurysm patency. At the same time we tried to manipulate microcateter and microguidewire in the aortic lumen. After that the aneurysm was microscopically inspected in order to verify the angiographic findings. Results. The aneurysms and the angiographic study could be performed in every animal. Four aortic and the renal artery aneurysms were not visualized in the angiography (totally thrombosed). The other five were partially thrombosed. Under microscopic aneurismal inspection could be found thrombus into the sac. The endovascular navigation was difficult due to the animal size. Conclusion. The bifurcation aneurysm model is a good microsurgical training. In our hands the aneurysms created had a high rate of spontaneous thrombosis. Because of animal size it is not a good model for endovascular training.

Aneurismas experimentales en cerdos con la técnica de Varsos / Varsos technique for experimental aneurysms in pigs

Objective. To achieve an aneurysm model in swine with a low rate of sponatneous thrombosis. Material and method. Five swines were operated using a two stages technique (Varsos technique). In the first step ten carotidjugular fistulas in the neck (4 internal and 6 external jugular vein) were performed. The two vessels formed a 45° angle after the anastomosis. After a week the venous component of the fistula was occluded in order to create an aneurysm. The aneurysms patency was angiographically studied fifteen days later. At this time several types of stents and coils could be released. Results . The fistula and the aneuysms could be performed without complications. Seven of 10 aneurysm were angiogaphically patent. Three were thrombosed, all of them were created with the internal jugular vein. A carotid stenosis was observed at the anastomosis site in a thrombosed aneurysm. Conclusions. The Varsos technique in swines, specially when performed with the external yugular vein has a low rate of spontaneous aneurysm thrombosis.

Treatment of experimental saccular aneurysms of carotid arteries with three kinds of covered stents in canine models / 介入放射学杂志

Objective To assess the effectiveness and safety and biocompatibility of balloon-expanding stainless steel stents (SSS) covered with polyurethane membrane (PUM), expanding poly teflon ester membrane(ePTFEM)and biomembrane (BM) in the treatment of experimental saccular aneurysms of carotid arteries in canine models.Methods 36 experimental saccular aneurysms of carotid arteries in 20 canines were created successfully by sugery. Experimental aneurysms were treated with covered stents including twelve PUM-SSS, twelve ePTFEM-SSS and twelve BM-SSS for each twelve canines repectively. They were placed endovascularly in the common carotid arteries covering the orifice of aneurysms. Follow up angiography was performed immediately after the procedure and 2, 4 and 12 weeks afterwards under the control of conventional anticoagulation. The animals were then sacrificed for histopathologic and statistical investigation. Results 36 stents were placed successfully in the target arteries. The complete patency rates of PUM-SSS, ePTFEM-SSS and BM-SSS were 25.0%, 41.7% and 91.7% respectively. Histological analysis indicated that all treated aneurysmal pouches were filled with thrombus. Stent wires were found to be located deep within the vessel wall and encased by extension of the tunica intima. Endothelialization of BM-SSS groups already began at the 2nd week which was earlier than that of PUM-SSS and ePTFEM-SSS. Various degrees of degenerative cells were seen under the transmission electron microscopy without surface erosion of stents. Conclusion Placement of covered stent endovascularly is expedient, safe, and effective. BM-SSS provides the best mechanical behavior, physiochemical stability, anticoagulative ability and biocompatibility.

Microsurgical Creation of Aneurysms in the Carotid Artery of Rats

To investigate the role of internal elastic lamina in the formation of an aneurysm and the pathological progression of the aneurysmal wall and neck area, in a series of 32 adult rats, a small discrete mechanical lesion was made following an arteriotomy on the common carotid artery. Through the arteriotomy site, the lesion was made in the intima of the opposite side of the arterial wall by microsurgical technique at the proximal site to the bifurcation of the common carotid artery. Surgical sites of vessels were inspected grossly and light microscopically at intervals of 1, 4, 8 and 12 weeks(each group : 8 animals). Among the 32 animals, well defined aneurysms were seen in 15. In histological examination of the aneurysms, the internal elastic lamina almost disappeared or fragmented at the level of the aneurysmal neck. The aneurysmal wall was composed of only collagen fibers without evidence of elastic fibers. The aneurysmal wall and neck thickened progressively with collagen deposits. These aneurysms were similar to the human aneurysm histologically. This technique provides an experimental surgical formation of aneurysm and lends support to the important role of internal elastic lamina in the formation of an aneurysm. This experiment also showed progressiv thickening of the aneurysmal wall with collagen deposits.