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The arterial grafts currently in use are classified into five basic categories; 10 different commercially available prostheses were chosen to represent these categories. The Vascutek and Bionit are made from knitted Dacron and have medium porosity, requiring preclotting by the surgeon. The DeBakey Soft Woven and Plasma TFE grafts are made from woven Dacron and have low porosity, not requiring preclotting under most circumstances. Also studied were woven and knitted grafts with leakage resistance referred to as "impervious" Dacron grafts: the Vascutek Gelseal, the Bard Albumin Coated DeBakey Vasculour II, the Microvel with Hemashield, and the albumin saturated, autoclaved DeBakey Soft Woven graft. Gore-Tex and Impra are expanded polytetrafluoroethylene grafts which do not require preclotting. For each type, five grafts 6 cm long and 8 mm in diameter were implanted in the descending thoracic aorta of healthy adult dogs for 16 weeks. The physical characteristics, biocompatibility, and healing patterns varied according to the structure and treatment of the grafts. Pretreatment with biomaterials during manufacture is quite effective in preventing transinterstices blood loss during implantation, but results in altered physical qualities, increased thrombogenicity and delayed healing in comparison to the effects of preclotting with autogenous blood at the time of implantation.

Longitudinal elasticities of whole human blood clot, whole canine blood clot, Factor XIII cross-linked fibrin, glutaraldehyde-fixed human albumin, and formaldehyde-fixed collagen, gelatin and collagen/gelatin were determined and normalized to human whole blood clot. Matrices of a knitted Dacron graft were then impregnated with albumin, collagen, and collagen/gelatin and their longitudinal elasticities were determined and normalized to a preclotted graft. Comparisons were also made for the longitudinal elasticities of a virgin graft, a manipulated control for a preclotted graft, and a manipulated control for the matrix-impregnated grafts. Flexibilities were then calculated based on the weights and elasticities of these grafts and normalized to the flexibility of the preclotted graft. Fibrin had twice and 39 times more longitudinal elasticity than human blood clot and collagen, respectively. The preclotted graft has longitudinal elastic properties similar to a virgin graft, and is 2.8, 2, and 1.4 times more elastic than the albumin, collagen and collagen/gelatin grafts, respectively. The preclotted graft was 2.5, 2, and 1.4 times more flexible than the albumin, collagen and collagen/gelatin grafts, respectively.

This paper compares the healing of supported knitted Dacron prostheses implanted in the descending thoracic aorta and in the subcutaneous carotid-femoral positions in each of 10 dogs. The descending thoracic aorta prostheses were 6 cm long and the carotid-femoral prostheses averaged 76 cm in length. The healing of four porous clinical axillofemoral grafts is compared to that of the experimental carotid-femoral grafts. There was little similarity between the healing observed in the descending thoracic aortic and subcutaneous positions; the descending thoracic aorta grafts healed rapidly and completely by eight weeks, with thrombus-free flow surfaces covered with confluent endothelial cells. However, the inner wall of the carotid-femoral grafts remained largely unhealed at one year, with endothelialization largely confined to a limited pannus ingrowth across the anastomoses. This indicates that the implant site in the dog is a primary determinant of the rapidity and completeness of healing. The clinical axillofemoral grafts explanted after 20 months to six and one-half years exhibited healing characteristics that were similar to those seen in the carotid-femoral position in the dog. These findings suggest that valid comparisons of interspecies healing require data obtained from similar implant locations. They present a challenge to the previously held concepts of major interspecies differences in speed and extent of tissue ingrowth based on data obtained from noncomparable implant sites.

A new carotid-femoral experimental model has been developed which has significant clinical relevance to human limb salvage bypass grafting in the areas of graft length, hemodynamics and tissue environment. More significantly, the graft healing pattern observed with this model is similar to what is seen in humans. Therefore, this experimental model provides a challenging and critical site for dynamic healing studies and comparisons of different types of vascular prostheses.

The effects of tissue ingrowth on the compliance of porous Dacron grafts were studied in 8 mm external-velour warp-knit Dacron grafts implanted in the canine descending thoracic aorta. The compliance of these grafts was measured before implantation and after implant periods of two weeks and one, two, four, and six months. Compliance, which initially was 0.043 +/- 0.008% mm Hg, decreased less than 10% after implantation (no statistical difference at p less than 0.05). No anastomotic neointimal hyperplasia was observed. Although the total thickness of the graft wall increased two- to three-fold after implantation, the benign healing process observed in this study had very little influence on graft compliance followed to six months.