Endovascular Repair of Thoracic Aortic Aneurysm in Dogs: Evaluation of a Nitinol-Polyester Self-Expanding Stent-Graft

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Abstract
Purpose: To validate the ease of deployment and in vivo healing performance of a nitinol-polyester self-expanding stent-graft using a canine thoracic aortic aneurysm model. Methods: Arterial aneurysms were surgically created in 8 dogs by sewing a polyester patch onto the anterior side of the thoracic aorta. The nitinol-polyester self-expandable stent-grafts (Cragg EndoPro System 1) were implanted transluminally via the femoral route and deployed at the site of the thoracic aneurysm. Aneurysm exclusion and endograft patency were assessed by angiography after implantation and before animal sacrifice at scheduled periods ranging from 1 week to 3 months. The explanted specimens were examined with magnetic resonance imaging (MRI) to study the position of the stent-graft with respect to the aneurysmal sac. Histological analysis using light microscopy and scanning electron microscopy was performed to examine the inflammatory response and healing characteristics of the device. Results: Seven of 8 stent-grafts were implanted successfully; a bend occurred within the aneurysmal sac in 1 dog, which led to continued perfusion of side branches. This endoleak sealed spontaneously within 1 week, and complete exclusion of the aneurysms in all 8 animals continued throughout implantation. At the time of explantation, all devices were structurally intact and well positioned in the aneurysmal sac. At 1 week, the luminal surface displayed a thin layer of thrombotic matrix, which was gradually replaced by a collagenous internal capsule with endothelial-like cell coverage along both ends of the stent-grafts at 2 and 3 months. No exacerbated inflammatory reaction due to either the nitinol wires or the polyester sleeve was observed after 3 months of implantation. Conclusions: This short-term in vivo study of a nitinol-polyester self-expanding endograft demonstrated the effective exclusion of thoracic aneurysms with a satisfactory healing response and no excessive tissue or inflammatory reactions.

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