Fundamental study on safety of cavered retrieval ncetallic stent

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Experimental Study on Covered Retrieval Expandable Metallic Stent.Summary : Purpose is to evaluate the efficasy of bared retrieval expandable metallic stent (REMS) and covered REMS in canine inferior vena cava. Meterials are as follows ; eleven adult dogs underwent the placement of bared REMS and six dogs underwent covered REMS with polyurethance, dacron and polytetrafuluoroethylene. Round stainless steel with diameter 0.35mm, twisted stainless steel thread with diameter 0.2mm and nylon surgical thread were used. The stainless steel wire was made into a cylindrical body with 12 zig zag hairpin bends, six bends of one side were twistcd to form small round loops. The loops were encircled by the stainless steel thread. Every two bends from neighboring bodies were connected by stainless steel thread. The retrieval set consists of a stainless steel hook with a rotating handle, long sheath and a Teflon rod. Results : After 1 week placemcnt, the bared REMS could be removed from IVC but over two weeks bared REMS and covered REMS could not be removed. Angiography showed the patency of the IVC lumen in all cases with bared REMS but occlusion in all cases with covered REMS.Pathological fidings showed incompletely covered intima on the surface of the bared REMS after 1 week placement and completely covered intima over 2 weeks. In covered REMS,the red thrombus and incompletely covered intima were noted. It is not acceptable for covered REMS to be tried to use for the obliterative IVC lesion.