Polyester arterial prostheses. Recent developments from the Czech Republic and Poland.

To evaluate recent developments in the design and production of polyester vascular prostheses in eastern Europe, a series of in vitro physical and chemical tests and an in vivo study was performed on three new prototype devices from the Czech Republic and one from Poland. The in vitro results for these four prostheses, referred to as the Ra-1n (warp knitted, uncrimped), Ra-1v (warp knitted, crimped), Mikrofroté (weft knitted, uncrimped), and Dallon (warp knitted, crimped) prostheses, were compared against values for three commercial devices of western origin, namely the Triaxial, the Vasculour II, and the Cooley II grafts. The animal trial involved implanting the four prototype devices as a thoracoabdominal bypass in dogs for eight different periods ranging from 4 hrs to 6 months and undertaking histologic and structural investigations on the retrieved grafts. Because of its poor long-term dimensional stability in vivo, the continued use of a weft knitted structure, like the Mikrofroté prosthesis, is to be deprecated. Conversely, the introduction of a more dimensionally stable warp knitted structure in three prototypes is to be acknowledged. However, the presence of surface contaminants was most likely responsible for the excessive inflammatory reaction generated by all four prostheses during the first month in vivo, which resulted in delayed healing performance. In addition, an unusually high surface carbon-oxygen ratio suggests that the crimping process needs further refinement. Improved cleaning and packaging procedures are essential before these products can complete against existing commercial prostheses of western origin. In conclusion, these new developments illustrate that the technology of warp knitting, which is now spreading worldwide, should be evaluated.

Soft filamentous woven polyester arterial prosthesis from China.

Woven polyester arterial prostheses have traditionally been known for their tight construction and smooth surface which has limited their healing capacity and resulted in poor attachment of their internal and external capsules. A new woven prototype has recently been developed in the Peoples' Republic of China. Among its unique features are its high physical porosity, softness and flexibility. This study undertook a series of in vitro tests to characterize its structure and physical properties in comparison with four commercial polyester grafts of North American origin. In addition, an animal trial was completed in which the new prototype was implanted as an infrarenal aortic substitute in 20 dogs for periods ranging from 4 h to 12 month. The in vitro tests confirmed a unique lightweight, highly porous, satin weave construction. Because of its high water permeability, preclotting was necessary before implantation. Once preclotted and installed, no significant blood loss was observed, and 19 of the 20 grafts remained patent at the sacrifice. Rapid full-width healing was achieved with tightly bound capsules, and more extensive tissue ingrowth was observed. Further work is needed to evaluate its long-term durability as an arterial substitute.

Cytocompatibility of albuminated polyester fabrics.

An alternative to the usual technique of preclotting porous textile vascular prostheses prior to surgical implantation is to render them impermeable to blood by impregnation with a cross-linked albumin filler matrix. This material subsequently becomes the foundation for cellular development. The compatibility of such impregnated fabrics with newly formed endothelial cells has been evaluated by an in vitro organotypic culture method. This technique enables the characterization and numeration of cells that develop on blood contact surfaces and enables determination of their rate of development. Woven, knitted, and velour fabrics were evaluated following coating with albumin and either storage in Tyrode solution or 40% ethanol or desiccation by critical point drying. Preclotted cardiovascular repair fabrics prepared according to conventional surgical protocol served as controls. The identification of the newly formed cells was confirmed histologically. The most extensive and rapid cellular development was observed on the woven fabric and is believed may have resulted from the smoother surface topography of this substrate. Good cellular development was noted particularly on fabrics which had been stored in Tyrode solution. Ethanol had a deleterious effect on the apparent compatibility.