Comparison of a Microporous Thermoplastic Polyurethane–covered Stent with a Self-expanding Bare Nitinol Stent in a Porcine Iliac Artery Model

• Published in: Journal of vascular and interventional radiology Vol. 20; no. 7; pp. 927 - 935
• Main Authors: Radeleff, Boris, MD, Grenacher, Lars, MD, PhD, Christoph, Patricia, MD, Sommer, Christof M., MD, Stampfl, Ulrike, MD, Ramsauer, Stefanie, MD, Henn, Tina, MD, Kurz, Patrick, MD, Lopez-Benitez, Ruben, MD, Berger, Irina, MD, PhD, Richter, Goetz M., MD, PhD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2009
• Subjects: Alloys - adverse effects; Alloys - chemistry; Animals; Blood Vessel Prosthesis - adverse effects; Coated Materials, Biocompatible - chemistry; Disease Models, Animal; Equipment Design; Equipment Failure Analysis; Graft Occlusion, Vascular - diagnosis; Graft Occlusion, Vascular - etiology; Hot Temperature; Humans; Iliac Artery - diagnostic imaging; Iliac Artery - pathology; Iliac Artery - surgery; Plastics - adverse effects; Plastics - chemistry; Polyurethanes - adverse effects; Polyurethanes - chemistry; Porosity; Radiography; Radiology; Stents - adverse effects; Swine; TPU; thermoplastic polyurethane
• ISSN: 1051-0443; 1535-7732
• DOI: 10.1016/j.jvir.2009.04.044

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.