Abdominal aortic healing associated with a thin-walled Dacron-covered endovascular graft in a canine model.

Purpose: To characterize the healing response associated with an experimental endovascular graft (EVG) by examining the lumen of the prosthesis and the native vessel wall responses after implantation in a canine model. Methods: An endovascular graft (EVG) constructed of hookless self-expanding nitinol springs covered by an ultrathin Dacron fabric was placed in the abdominal aorta of 8 dogs following femoral artery catheterization. After 12 weeks, specimens were subjected to histological and immunocytochemical testing to quantitatively and qualitatively analyze the cellular makeup of the luminal and abluminal tissues. Results: Gross examination revealed a glistening, thrombus-free luminal surface on all prostheses, which was confirmed by scanning electron microscopy. The EVGs were well incorporated into the aortic wall, leaving a concentric, smooth flow surface. Immunocytochemistry verified the presence of von Willebrand factor-positive endothelial cells on the luminal surface and alpha-smooth muscle cell actin-positive smooth muscle and/or fibroblast cells in the subendothelial space. A sparse inflammatory response and a paucity of proliferating nuclear cell antigen-positive cells were noted within the neomedial lining adjacent to the graft material. In addition, a rich vaso vasorum-like plexus of microvessels was evident within the neomedial tissue. The native vessel wall upon which the EVG impinged was largely unaffected. Conclusions: These data demonstrate that placement of an experimental EVG in the canine abdominal aorta elicits a healing response that is distinct from interpositional vascular grafts. Results from this study have particular relevance to the proximal and distal anastomotic neck regions.