Search

Woven and knitted cardiovascular prostheses are tubular structures made of polyester filaments. They present particular mechanical properties linked to the wavy form of their walls, allowing them to be used in curved configurations. Pulsatile blood flows have been studied in bent textile prosthesis. The results obtained showed velocity peaks involving high-shear stress zones and turbulence phenomenon inside the graft. The flow velocity distribution near a prosthetic surface is strongly influenced by the crimping morphology. A local flow analysis is imperative in understanding pathologies implying hemodynamic factors and in optimizing the prosthesis design. [ABSTRACT FROM AUTHOR]

The article describes a concept of heart valve prosthesis, based on the use of textile material. The goal of the work is to make a fabric prosthesis by using woven yarns made up of polyester. The method for prothesis manufacturing is described. Fabric prosthesis shows encouraging behavior in vitro such as good flexibility, reduced permeability with adapted fabric parameters.

The article examines the nature of morphological changes induced by ageing on polyethylene terephthalate fibers extracted from explanted prostheses. The method for testing a commercial Warp-knitted prosthesis is described. It was found that the implantation involves a transformation of the original crystalline structure as shown by the modulate differential scanning calorimetry scans of yarns extracted from different prostheses.

The article reports on the development of a device that is able to follow the total constraint in the textile structure, the field of deformation of a face and the thermal losses generated in the filaments by friction and deformation in vascular textile prostheses (VTP). The construction of the device on a classical dynamometer is described. Load-elongation curves provide a general knowledge of the mechanical properties of the prostheses.

The prosthetic explants collection in PET knitted prosthesis enabled us to count a great number of longitudinal ruptures close to the looping wale. Previous studies showed modifications of the polymer organization after a stay in the human body. To supplement these studies, we undertook circumferential traction tests, which partly simulated the action of a pressure in the prosthesis. As the localization of a rupture is often caused by a localization of the constraints, we used a video camera to make films of the knitting structure in order to highlight the behavior of a mechanical heterogeneity. This device also allowed us to define a global coefficient related to the deformability of the textile structure. The overall results showed that for similar prostheses, a structural heterogeneity existed. It then generated various behaviors which were constraint sources and thus of ruptures by mechanical fatigue. Therefore, our approach highlighted the possibility of an early study of the rupture zones' localization. For that study, the investigation methods require improvement. However, the heterogeneity of the mechanical behavior was not able to explain the entire ageing phenomenon. For example, the guide-line ruptures are not yet well understood. [ABSTRACT FROM AUTHOR]

Percutaneous aortic valve implantation has become an alternative technique to surgical valve replacement in patients with high risk for surgery. This technique is at its beginning and stents used for valve prostheses remain standard vascular stents. These stents are, however not designed to undergo heart valve stress. They do not match the aortic environment geometry, and induce exaggerated tissue traumatism. Reduced implant lifetime may therefore be expected. The purpose of the present work is to evaluate in vitro the technical feasibility of noninvasive aortic valve replacement with a novel more specific stent. This stent is especially adapted to its implantation environment with a design that matches the shape of the aortic root while respecting the valve functions. We present a design, a manufacturing process and in vitro peiformances for the stent under static pressure loading and pulsatile flow. The stent shows good dynamic behavior in keeping position imposed at implantation time and in matching the aortic root dimensions changes. Prosthesis static and dynamic regurgitation are evaluated and show values close to those obtained with other commercially available prostheses. [ABSTRACT FROM AUTHOR]