Comparison of a Microporous Thermoplastic Polyurethane–covered Stent with a Self-expanding Bare Nitinol Stent in a Porcine Iliac Artery Model
Received 3 February 2008; received in revised form 4 April 2009; accepted 7 April 2009. published online 04 June 2009.
Purpose
To compare outcomes with a thermoplastic polyurethane (TPU)–covered self-expanding nitinol stent-graft (TPU graft) with those of a bare self-expanding nitinol stent in a porcine model.
Materials and Methods
Fourteen TPU grafts and 14 commercially available bare nitinol stents were implanted, one each, in the iliac arteries of 14 minipigs. Follow-up was performed at 1 week (six animals), 4 weeks (four animals), and 12 weeks (four animals). The primary study endpoint was in-stent stenosis assessed with quantitative angiography and microscopy. Secondary endpoints were injury, inflammation, and endothelialization.
Results
After 1 week, the maximum percentage luminal loss was significantly greater in TPU grafts (average, 16.2%; range, 0.0%–35.8%) than in bare nitinol stents (8.2%; 0.0%–17.3%) (P = .04). Three of the four TPU grafts were occluded after 4 weeks, and all four TPU grafts were occluded after 12 weeks. Binary stenosis was seen in three of four bare nitinol stents after both 4 and 12 weeks. At 4-week follow-up, the average percentage luminal loss was significantly greater in TPU grafts (85.2%; 40.8%–100%) than in bare nitinol stents (49.5%; 37.9%–62.4%) (P = .003). The difference in neointimal height and percentage average stenosis between TPU grafts (1,028.7 μm and 68.4%) and bare nitinol stents (1,033.6 μm [918.0–1,118.40 μm] and 68.1% [60.44%–71.99%]) was not statistically significant. After 12 weeks, the average percentage luminal loss was 100% in TPU grafts due to occlusion of all stent-grafts and 24.9% (8.0%–63.9%) in bare nitinol stents (P = .011).
Conclusions
TPU grafts failed to provide improved patency compared with the bare nitinol stents because of excessive neointimal growth and subsequent occlusion. In addition, the bare nitinol stents showed considerable in-stent stenosis at angiography and microscopy.
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