GRAFT HEALING OF STRETCHED ePTFE IMPLANTED WITHIN A BABOON MODEL

摘要

Arterial grafts need to exhibit two properties: a flow surface with low thrombogenicity and minimal intimal thickening. For well over thirty years, researchers focused their attention upon the healing properties of graft material. Beginning with Wesolowski's 1961 work, researchers concluded that porous synthetic grafts demonstrated improved healing properties (1). Most recently, Clowes, et al., documented that ePTFE with a nominal porosity of 60 μm healed at one month with complete endothelial coverage, uniformly distributed pseudointimal growth, and improved intimal stability (2). These results contrasted to what was found when porosity was deceased to an internodal distance of 10 or 30 μm. Hemodynamic parameters significantly impact graft healing. For native vessels, researchers established that high flow environments inhibit intimal thickening (3-5). For ePTFE grafts, Clowes, et al., documented that a high shear environment (24+-8 dynes/cm~2) decreased intimal thickening by about 50% and notably decreased smooth muscle cell proliferation and volume (6). Within an ePTFE graft, a newly introduced high shear environment was shown to reduce the area of already formed intima (7). While very illustrative, these studies failed to completely describe how the healing properties of ePTFE change with alterations in the material's ultrastructure. With the growing popularity of endovascular stent grafts, this question has assumed greater importance. When deploying an endovascular stent graft, the angioplasty balloon dilatation radially stretches the surrounding ePTFE and changes its ultrastructure. We therefore investigated how changes in graft ultrastructure affected healing in comparison to unaltered graft material exposed to a high shear stress environment.