Dr. Gary J. Becker Young Investigator Award: Comparison of small-diameter type 1 collagen stent-grafts and PTFE stent-grafts in a canine model - Workin progress

PURPOSE: To report an in-progress experiment in a canine model in which two types of small-diameter stent-grafts-one constructed of polytetrafluoroeth ylene (PTFE) and the other of a new, type I collagen material-were compared regarding vessel patency, intimal hyperplasia formation, and tissue reacti on. 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 ballo on-expandable stainless-steel stents wrapped with either PTFE or a new type 1 collagen graft. Stent-grafts were placed in deep femoral arteries bilate rally (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 bas ed on angiographic findings as well as thickness and area of neointimal hyp erplasia were compared at each time point and compared with use of the Stud ent 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 f ive patent collagen stent-grafts. All five patent PTFE stent-grafts showed demonstrable in-stent stenosis (10%-60%), indicating a trend toward improve d patency in collagen stent-grafts versus PTFE stent-grafts (P = .07). Neoi ntimal hyperplasia was absent at 2 weeks in the collagen stent-grafts. Neoi ntimal thickness increased to a maximum of 360 mum at 12 weeks in the colla gen 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 d emonstrate excellent patency rates and favorable histologic findings. The t ype I collagen stent-graft technology merits further developmental efforts in preclinical models.