Heart valves from polymeric fibers: potential and limits

Transcatheter aortic valve implantation (TAVI) has become today a popular alternative technique to surgical valve replacement for critical patients. However, with only six years follow-up on average, little is known about the long-term durability of transcatheter implanted biological tissue. Moreover, the high cost of biological tissue harvesting and chemical treatment procedures favor the development of alternative synthetic valve leaflet materials. In that context, thin, flexible and porous textile constructions could be considered as interesting candidates. However, these constructions must be strong enough to withstand the load applied on the leaflet especially in aortic position. Moreover, the interaction of textile material with living tissue should be comparable to biological valve tissue, and the foreign body reaction (FBR) as well as the calcification mechanisms should be controlled. In the frame of heart valve tissue engineering strategies, the use of bioresorbable polymer scaffolds is expected to limit that FBR. However, to precisely control the degradation of the polymer is not trivial. Conversely, when permanent textile polymers are considered, the porosity of the fibrous scaffold tends to induce exaggerated tissue ingrowth which may prevent the implants from remaining flexible. In that context, the ideal synthetic fibrous valve leaflet remains to be found. The purpose of this study was to investigate the possible strategies which have been adopted over the last 50 years regarding the use of textile as heart valve leaflet material. Results showed that textile presented potential, despite remaining strong challenges. It came out that hybrid textiles combining bioresorbable and permanent polymer fibers arranged in both non-woven and woven or knitted way could probably help providing strength and generating appropriate tissue ingrowth.