Healing response of normal canine aorta and iliac artery to a nitinol stent encapsulated in carbon-lined ePTFE

Purpose: To evaluate the healing response of normal canine arteries to a se lf-expanding nitinol stent encapsulated in carbon-lined expanded polytetraf luoroethylene (ePTFE). Methods: Twenty-eight dogs were divided into aortic (n = 18) or iliac (n = 10) groups. In the latter, 2 animals were assigned to implantation interval s of 7, 30, and 90 days, respectively; 4 were designated for 180-day implan tation. Half of the animals in each subgroup received a second overlapping stent-graft in one iliac artery. In the aortic cohort, 6 animals were assig ned to the 180-day implantation group (2 with dual devices) and 3 to each o f the others (1 dual implantation in each group). The devices were evaluate d with angiography and intravascular ultrasound at implantation and explant ation. After harvesting and gross examination, the specimens were examined microscopically and with scanning electron microscopy. Results: The 49 implanted devices (24 aortic and 25 common iliac) were all widely patent at explantation, save for 2 iliac stents that had moderate (< 40%) stenosis. No neointima was present at the 7-day interval. All stents w ere covered by thin neointima (<150 mum) at 30 days. At 180 days, an endoth elial lining was present in the proximal and distal segments of all stents; in 4 of the 6 aortic stents, this endothelial lining was complete, whereas none of the iliac devices had endothelium in the midsegment at 180 days. A t 1 year, 2 of the aortic specimens had an incomplete endothelial lining, w hereas the lining was complete in the third. There was no evidence of stent -graft migration or inflammation associated with any device. Conclusions: The carbon-lined ePTFE-encapsulated stent is a novel approach to arterial stenting. The progressive endothelialization and lack of inflam matory reaction may provide improved long-term patency. Further study of th is stent-graft design is warranted.