The effect of nonporous PTFE-covered stents on intimal hyperplasia following balloon arterial injury in minipigs

Purpose:To report an experimental study investigating the ability of nonpor ous polytetrafluoroethylene (PTFE) covering on a metallic stent to retard t he development of neointimal hyperplasia (NIH). Methods: Three groups of Hanford miniature swine underwent standardized bal loon injury to both external iliac arteries. Group I animals (control) rece ived balloon injuries only. Group II had the site of balloon injury support ed by a properly sized, balloon-expandable Palmaz stent placed directly ove r the injury site. Group III animals received a Palmaz stent covered with P TFE graft. All animals underwent arteriography immediately after interventi on and again prior to sacrifice and specimen harvest at 4 weeks. The specim ens were examined grossly and histologically at he proximal, middle, and di stal segments for NIH development. Results: Uncovered stents developed significantly more NIH (p < 0.0001) and greater luminal narrowing (p < 0.001) than the controls. PTFE-covered sten ts (group ill) exhibited less NIH (p < 0.001) and luminal reduction (p < 0. 01) than bare stents (group II) at the middle portion of the stent-graft, b ut the PTFE cover had no effect on NIH and lumen reduction at the proximal or distal ends of the prosthesis. Conclusions: PTFE-covered stents retarded NIH at 4 weeks, but only at the m idportion of the devices; the covering did not prevent neointimal pannus in growth at the proximal and distal ends.