title: Retrievable IVC square stent filter: experimental study.
abstract: OBJECTIVE
  In vitro and in vivo evaluation of a new retrievable, home-made, inferior vena cava (IVC) Square stent filter (SSF) with two trapping levels.
  
  
  METHODS
  In vitro, the SSF was compared in a flow model with the stainless steel Greenfield filter (SGF) for emboli-trapping efficiency by serially passing 300 emboli of 3 and 6 mm in diameter and 15-30 mm in length in each type of filter. Nine swine were used for the in vivo testing of the SSF for deployment and retrievability, emboli-trapping efficiency, stability, and self-centering ability and two were used (total of 11 swine) for testing repositioning and retrievability of the SSF at 2 weeks and for gross and histologic IVC changes at 2 months.
  
  
  RESULTS
  In vitro, the SSF and SGF had similar efficiency in trapping large emboli but the SSF had significantly better efficiency than the SGF for trapping all sizes of emboli (91.7% vs 81%), medium size emboli (93% vs 80%), and small emboli (86% vs 69%). Efficiency decreased in both filters from the first to the fifth embolus in each series but was still significantly better for the SSF. With the SSF, 89% of emboli were caught at the primary and 11% at the secondary filtration level. In the nine animals used for acute studies, the SSF was easily placed in all 27 attempts, assumed a central position 26 times, and was easily retrieved in 21 of 22 attempts. One tilted filter needed additional manipulation for retrieval. During emboli injection in five swine, the SSF had 97.2% emboli-trapping efficiency and demonstrated good stability. In the two animals used for longer-term evaluation, the filters were easily retrieved 2 weeks after implantation. Histologic evaluation at 2 months showed neointimal proliferation around the SSF wires in contact with the IVC wall, which was otherwise normal.
  
  
  CONCLUSIONS
  The SSF is a promising filter. It is easy to place and retrieve, is stable after placement, and has high efficiency for trapping emboli. Promising results justify further experimental and eventual clinical studies with a commercially manufactured SSF.
authors.affiliation: Dotter Interventional Institute, Oregon Health Sciences University, Portland 97201, USA.
authors.forename: D
authors.initials: D
authors.lastname: Pavcnik
authors.forename: B T
authors.initials: BT
authors.lastname: Uchida
authors.forename: F S
authors.initials: FS
authors.lastname: Keller
authors.forename: C L
authors.initials: CL
authors.lastname: Corless
authors.forename: J
authors.initials: J
authors.lastname: Rösch
mesh_terms: D000818:Animals; D004867:Equipment Design; D011655:Pulmonary Embolism / Q000517:prevention & control; D013193:Stainless Steel; D013552:Swine; D016306:Vena Cava Filters; D014682:Vena Cava, Inferior / Q000473:pathology
chemical_list: D013193:Stainless Steel