title: Use of covered stents in the central vein: a feasibility study in a canine model.
abstract: OBJECTIVE
  To evaluate the feasibility of using covered stents vs. bare stents in a model of central vein stenosis with an arteriovenous graft created to mimic the conditions in hemodialysis patients.
  
  
  METHODS
  In 7 mongrel dogs, an expanded polytetrafluoroethylene-covered nitinol stent was placed in one common iliac vein and a bare stent was placed in the contralateral vein. Arteriovenous grafts were created bilaterally between the common femoral artery and vein to induce endothelial damage. Neointima formation in the covered stents was compared to the bare stents at 12 weeks using microscopy and histochemical staining.
  
  
  RESULTS
  Two dogs were excluded due to thrombosis and infection of the arteriovenous grafts, but all stents in the remaining 5 dogs were patent. Smooth, complete neointimal coverage was observed on the inner surface of all the covered stents without intraluminal thrombus. In contrast, incomplete neointimal coverage was seen in all bare stents, with small focal thrombi adhering to the neointima on 3 bare stents. Focal nodular neointimal hyperplasia with denudation of the endothelium was observed in only 2 bare stents. Mean neointimal thickening was significantly greater in the covered stents. Eccentric neointimal thickening was observed at the inflow and outflow segments of both types of stents.
  
  
  CONCLUSIONS
  Covered stents are technically feasible for the treatment of central vein stenosis, and they demonstrate complete, smooth neointimal coverage in normal central veins, but they also display greater neointimal thickening than bare stents.
authors.affiliation: Department of Radiology, Chungnam National University Hospital, Daejeon, South Korea.
authors.forename: Byung Seok
authors.initials: BS
authors.lastname: Shin
authors.forename: Mi-hyun
authors.initials: MH
authors.lastname: Park
authors.forename: Gyeong Sik
authors.initials: GS
authors.lastname: Jeon
authors.forename: Byung Mo
authors.initials: BM
authors.lastname: Lee
authors.forename: Kichang
authors.initials: K
authors.lastname: Lee
authors.forename: Dae-Young
authors.initials: DY
authors.lastname: Kang
authors.forename: Sung Gwon
authors.initials: SG
authors.lastname: Kang
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Han
mesh_terms: D000497:Alloys; D000818:Animals; D001163:Arteriovenous Anastomosis / Q000473:pathology*; D001807:Blood Vessel Prosthesis / Q000009:adverse effects*; D003251:Constriction, Pathologic / Q000601:surgery*; D004195:Disease Models, Animal; D004285:Dogs; D005240:Feasibility Studies; D005263:Femoral Artery / Q000601:surgery*; D007084:Iliac Vein / Q000473:pathology* / Q000601:surgery; D058426:Neointima / Q000473:pathology*; D011138:Polytetrafluoroethylene; D011474:Prosthesis Design; D006435:Renal Dialysis / Q000009:adverse effects / Q000295:instrumentation*; D015607:Stents / Q000009:adverse effects
chemical_list: D000497:Alloys; C013616:nitinol; D011138:Polytetrafluoroethylene