Polytetrafluoroethylene-encapsulated stent-grafts: Use in experimental abdominal aortic aneurysm

PURPOSE: To evaluate expanded polytetrafluoroethylene (ePTFE) encapsulated stents for the treatment of aortic aneurysms with emphasis on the blood and tissue-material interactions. MATERIALS AND METHODS: Experimental aortic aneurysms were created in dogs b y enlarging the aortic lumen with an abdominal fascial patch. Twenty animal s underwent endoluminal repair after allowing the surgically created aneury sm to heal for 2 months prior to transluminal aneurysmal exclusion. The dev ice used consisted of an 8-cm-long ePTFE encapsulated stent graft. The anim als were killed in groups at 1 week and at 1, 2.25, 6, and 12 months. Speci mens were processed for histologic and luminal surface studies. RESULTS: Before the animals were killed, aortography demonstrated two throm bosed aortae in the 6-month group and two endoleaks in the 12-month group. Endothelialized neointima extended into the proximal and distal portions of the prosthetic lumen, with minimal cell coverage in the center of the graf t. The overall percent surface area covered by endothelialized neointima wa s 22% +/- 6% at 6 months and 18% +/- 10% by 1 year (P = .75), Histologic ex amination demonstrated minimal tisue penetration into the ePTFE, CONCLUSION: Transluminal exclusion of abdominal aortic aneurysms by encapsu lated stent-graft is easily acomplished, With this device, tissue coverage and penetration of the stent graft is limited and does not tend to increase with time.