PURPOSE: To report an in-progress experiment in a canine model in which two types of small-diameter stent-grafts-one constructed of polytetrafluoroethylene (PTFE) and the other of a new, type I collagen material-were compared regarding vessel patency, intimal hyperplasia formation, and tissue reaction. MATERIALS AND METHODS: Six mongrel dogs weighing 30-35 kg were used. Stent-grafts of 4-mm diameter and 20-mm length were constructed with use of balloon-expandable stainless-steel stents wrapped with either PTFE or a new type 1 collagen graft. Stent-grafts were placed in deep femoral arteries bilaterally (PTFE on one side, collagen on the other). Animals were followed for 2 weeks (n = 2), 6 weeks (n = 2), or 12 weeks (n = 2). Percent stenosis based on angiographic findings as well as thickness and area of neointimal hyperplasia were compared at each time point and compared with use of the Student t test. RESULTS: All devices were patent in the immediate postimplantation period. Five of six collagen stent-grafts and five of six PTFE implants were patent at follow-up. In-stent stenosis was undetectable angiographically in all five patent collagen stent-grafts. All five patent PTFE stent-grafts showed demonstrable in-stent stenosis (10%-60%), indicating a trend toward improved patency in collagen stent-grafts versus PTFE stent-grafts (P = .07). Neointimal hyperplasia was absent at 2 weeks in the collagen stent-grafts. Neointimal thickness increased to a maximum of 360 mum at 12 weeks in the collagen stent-grafts. For PTFE stent-grafts, neointimal hyperplasia was present in all samples and reached a maximum of 770 mum at 12 weeks (P = .03). CONCLUSIONS: Even in small-diameter vessels, type 1 collagen stent-grafts demonstrate excellent patency rates and favorable histologic findings. The type I collagen stent-graft technology merits further developmental efforts in preclinical models.
