Tissue Responses to Endovascular Stent Grafts for Saccular Abdominal Aortic Aneurysms in a Canine Model

We investigated tissue responses to endoskeleton stent grafts for saccular abdominal aortic aneurysms (AAAs) in canines. Saccular AAAs were made with Dacron patch in 8 dogs, and were excluded by endoskeleton stent grafts composed of nitinol stent and expanded polytetrafluoroethylene graft. Animals were sacrificed at 2 months (Group 1; n = 3) or 6 months (Group 2; n = 5) after the placement, respectively. The aortas embedding stent grafts were excised en bloc for gross inspection and sliced at 5 to 8 mm intervals for histopathologic evaluation. Stent grafts were patent in all except a dog showing a thrombotic occlusion in Group 2. In the 7 dogs with patent lumen, the graft overhanging the saccular aneurysm was covered by thick or thin thrombi with no endothelial layer, and the graft over the aortic wall was completely covered by neointima with an endothelial layer. Transgraft cell migration was less active at an aneurysm than at adjacent normal aorta. In conclusion, endoskeleton stent grafts over saccular aneurysms show no endothelial coverage and poor transgraft cell migration in a canine model.