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Availability of graft material suitable for stent graft application is rather limited and ePTFE remains almost the only choice for small profile stent grafts. Here we demonstrate in a 90 days animal study based on ovine model peripheral artery stenting, that an UHMWPE membrane (Dyneema Purity® Membrane) shows great promise as an alternative graft material for use in vascular stent graft applications. In comparison to typical ePTFE, this thin and highly porous UHMWPE membrane is mechanically strong and isotropic with a breaking strength of ∼20 MPa, and hence is particularly suitable for making low profile stent grafts.
UHMWPE Membrane is manufactured via a proprietary gel-extrusion and bi-axially stretching process which leads to a highly porous and thin (3 g/m2 and < 20 μm thick) membrane. The UHMWPE Membrane covered stents used in this study were produced via a proprietary lamination process that encapsulates the nitinol stent. Four sheep (Ovis aries) weighing 50-60 kg were used for the current animal study. For each sheep, one test article and one control article Gore® Viabahn® covered-stent with CARMEDA® bioactive heparin surface (Gore-CA) were introduced via femoral access to the carotid or iliofemoral artery. On the day of termination (day 90) angiography was performed, where after animals were sacrificed and the target artery segments containing the test articles or the control articles were explanted. Before processing samples for further histological analysis, explanted arteries were grossly radiographed and photographed for macroscopic evaluation of vessel intactness and stent expansion.
Angiography shows that all implanted stent grafts, both test articles and control articles, in all four sheep were widely patent at 90 days. Histological analysis of both longitudinal and transverse sections of all implanted stent grafts, both test articles and control articles, show comparable graft apposition, tissue reaction and inflammatory response. In addition, histological results corroborate the widely patent status of the implanted stent graft at 90 days. Fig3 gives an example of the histological images of longitudinal and transverse sections of the stent graft in the right carotid artery for both UHMWPE covered stent and Gore-CA.
The results from angiographical, radiographical and histological analyses performed on all implanted stent grafts show that the UHMWPE covered stent does not exhibit inferior performance when compared to Gore-CA. Such findings suggest great promise of Dyneema Purity® Membrane to be used as an alternative synthetic graft material for vascular covered-stent, particularly low profile covered-stent applications.
ENDOVASCULAR: Peripheral Vascular Disease and Intervention