In Vivo Study of a High-Porosity Polytetrafluoroethylene Graft: Endothelialization, Fluid Leakage, and the Effect of Fibrin Glue Sealing

Abstract

Standard polytetrafluoroethylene (PTFE) grafts (30-microns internodal distance, ID) (ST grafts), high-porosity PTFE grafts (90 microns ID) (HP grafts), high-porosity PTFE grafts preclotted with autogenous blood (BHP grafts), and high-porosity PTFE grafts presealed with fibrin glue (FHP grafts) were implanted in both common carotid and femoral arteries of 18 dogs. Of the three high-porosity groups, the FHP graft showed the shortest bleeding time. Seromas and/or hematomas occurred as follows: ST grafts 1, HP grafts 7 (P < .05 vs ST), BHP grafts 5 and 2 with FHP grafts. Fibrin glue was observed in all histological sections of 1-week samples, but by 4 weeks it was almost totally absorbed. No endothelialization (ET) was measurable at 2 weeks. By 4 weeks ET extended for a short distance from each anastomosis and there were no significant differences between the four graft groups. At 18 weeks, the HP, BHP, and FHP grafts showed a significant increase in ET compared with the ST graft (P < .01) but there were no significant differences between the three types of high-porosity graft. The differences in patency rates and neointimal thicknesses did not reach statistical significance. High-porosity PTFE grafts showed superior endothelialization in dogs; however, the enlarged ID of PTFE grafts increased intraoperative bleeding and postoperative seroma formation. Fibrin glue sealant controlled bleeding through the graft wall without affecting graft healing, but its sealant effect was not enough to prevent late fluid leakage.

Lipid uptake in expanded polytetrafluoroethylene vascular grafts

“…In addition, the permeability tests point out that ePTFE vascular grafts may undergo postleakage as, for example, perigraft seroma formation (a collection of clear, sterile fluid), which has been observed when using vascular prostheses made of PTFE. [28][29][30] This fluid may therefore act as a de facto wettability medium, allowing not only its own transport through the wall of the vascular prosthesis, but also that of other molecules.…”

Accelerated neovascularization and endothelialization of vascular grafts promoted by covalently bound laminin type 1

“…For this reason, many investigations have evaluated methods to accelerate formation of a new endothelium using techniques such as endothelial cell transplantation,17–19 accelerated pannus ingrowth, and the focus of the present study, accelerated transinterstitial ingrowth 20, 21. Stimulants for transinterstital ingrowth have concentrated previously on two major efforts, namely incorporation of soluble endothelial cell growth factors to stimulate angiogenesis22 and physical changes in polymers to make them more porous and less restrictive to endothelial cell penetration 3, 5, 23, 24. Our efforts in the present study have focused on the use of immobilized extracellular matrix proteins to accelerate spontaneous endothelialization.…”

“…These studies also provide evidence that the mechanism responsible for the observed inhibition of spontaneous endothelialization of commercially available ePTFE is not a physical barrier to cell penetration through the interstices of this material. Several investigations have evaluated the use of experimental ePTFE of increased porosity with the hypothesis that this increased porosity is necessary for endothelialization 3, 5, 23, 24. The current study was performed using ePTFE with internodal distances identical to clinically used ePTFE vascular grafts.…”

“…20,21 Stimulants for transinterstital ingrowth have concentrated previously on two major efforts, namely incorporation of soluble endothelial cell growth factors to stimulate angiogenesis 22 and physical changes in polymers to make them more porous and less restrictive to endothelial cell penetration. 3,5,23,24 Our efforts in the present study have focused on the use of immobilized extracellular matrix proteins to accelerate spontaneous endothelialization. The rationale for the use of extracellular matrix proteins in these studies is based on significant evidence that endothelial cell function is regulated by extracellular proteins through the transmembrane protein integrin system.…”

“…Several investigations have evaluated the use of experimental ePTFE of increased porosity with the hypothesis that this increased porosity is necessary for endothelialization. 3,5,23,24 The current study was performed using ePTFE with internodal distances identical to clinically used ePTFE vascular grafts. The penetration of endothelial cells, and as illustrated, intact microvascular networks into the interstices of laminin type 1-treated ePTFE, provides evidence that porosity is not the critical element controlling polymer neovascularization.…”