Polytetrafluoroethylene Microprosthesis in the Venous System of the Rat

Abstract

In this study, a 2 mm internal diameter (i.d.) polytetrafluoroethylene (PTFE) microprosthesis was used in the venous system of the rat, to determine whether or not it could serve as an acceptable microvenous substitute. Forty Long-Evans rats were divided into four groups: Group 1-10 rats with autotransplant of an inferior vena cava segment; Group 2-10 rats with a segment substitution of the inferior vena cava by a 2 mm i.d. PFTE microprosthesis; Group 3-10 rats with a laterolateral portacaval shunt; and Group 4-10 rats with a portacaval shunt and interposition of a 2 mm i.d. PTFE microprosthesis (new model). The rats were sacrificed at different time intervals up to 100 days, with cavography (femoral access) in Groups 1 and 2 and spleenoportography (direct puncture of the spleen) in Groups 3 and 4, before sacrifice. In Group 1, a 100 percent patency was observed at a mean of 49 days; in Group 2, a 70 percent patency with a 30 percent stenosis at a mean of 39.4 days (p less than 0.05); in Group 3, a 100 percent patency at a mean of 42.5 days; and in Group 4, a 30 percent patency at a mean of 38.4 days (p less than 0.01). Results showed that the 2 mm i.d. PTFE microprosthesis placed in the venous system of the rat is not an efficacious procedure, and that the search for better microvenous substitutes should focus on those of biologic origin.

Hyaluronan‐based scaffold for in vivo regeneration of the rat vena cava: Preliminary results in an animal model

“…The most important novel finding is represented by the ability of proposed vascular prostheses to sequentially orchestrate vascular regeneration events needed for small vein reconstruction. The development of reconstructive venous surgery has been hampered by the lack of suitable graft materials 1–12. There are only few evidences in the literature about the possibility to substitute a vein tract with prosthesis 1–12.…”

“…As preliminary results have been very discouraging, a minimal number of studies have been carried out and much more research is needed in this area. small‐diameter prostheses have not left the laboratory, as they have been disappointing in their high rate of thrombosis, and are still considered unreliable 1–12. Several factors are thought to play an important role in prosthetic microvenous occlusion, such as the low‐flow state combined with the thrombogenity of the graft material.…”

“…Harvesting such grafts prolongs the operation time and may compromise free tissue transfers or replantations, and so it would be advantageous to have reliable synthetic microvascular prostheses of various sizes readily available 1–3. Synthetic vascular prostheses, such as Dacron fabric grafts and Polytetrafluoroethylene (ePTFE), have been developed to supplement the limited supply of native graft materials 4–12. They perform satisfactorily in high‐flow, low‐resistance conditions in peripheral arteries larger than 5 mm, but they are not bioactive and suitable for small caliber arterial and venous reconstructions.…”

“…Thus far, both clinical and experimental replacements of microvenous segments with prosthetic conduits have been largely unsuccessful due to thrombosis. Several factors are thought to be responsible such as the thrombogenicity of the graft material and the low‐flow‐rate 4–12. At present, microvascular prostheses have proved highly unsatisfactory once inserted in the venous system, and small‐diameter prostheses have not left the laboratory, as they have been disappointing in their high rate of thrombosis, and are still considered unreliable 4–12.…”

“…Several factors are thought to be responsible such as the thrombogenicity of the graft material and the low‐flow‐rate 4–12. At present, microvascular prostheses have proved highly unsatisfactory once inserted in the venous system, and small‐diameter prostheses have not left the laboratory, as they have been disappointing in their high rate of thrombosis, and are still considered unreliable 4–12. Recent studies have focused on ECM‐based biomaterials, such as proteoglycans and glycosaminoglycans (GAGs), which could be useful as scaffolds for vascular endothelial cell (EC) regeneration, due to their presence in the vascular intima and media, and their frequent amenability to chemical stabilization with little biological alteration 13–15.…”