Textile transcatheter heart valve prosthesis: state of the art

Abstract

Today, transcatheter aortic valve replacement (TAVR) has become a largely considered alternative technique to surgical valve replacement in patients who are not operable or patients with high risk for open chest surgery. However, the biological valve tissue used in the devices implanted clinically appears to be a fragile material when folded for lowdiameter catheter insertion purpose and released in calcified environment with irregular geometry. Textile polyester material is characterised by outstanding folding and strength properties combined with proven biocompatibility. It could therefore be considered to replace biological valve leaflets in the TAVR procedure. Different issues must, however, be addressed concerning the development of the fabric construction in order to make the material compatible with the valve-requested durability. The performances of a textile valve mainly depend on the ability of the fabric to undergo repeated cyclic loading, the ability of the fibrous construction to resist exaggerated tissue ingrowth with leaflet stiffening and the ability to be crimped into the catheter sheet. The purpose of the present work is to present how a polyester fabric material can address these critical issues, and how the material can be tuned in order to optimise the performance of the device. IntroductionToday, non-invasive valvular surgery, also called percutaneous surgery or transcatheter aortic valve replacement (TAVR), has become a technology of choice to relieve patients from valvular diseases like stenosis. Far less traumatic for the patient, this technique is also less expensive and less time-consuming, which makes it very attractive for the medical world.1,2 Its use is, today, limited to either non-operable patients or patients with high risk for open chest surgery. But the part of transcatheter procedures is expected to increase by 20% a year up to 2017 alone in Europe according to market forecast studies.3 Thus, non-invasive procedures can be expected to concern non-critical patients in the very future. However, in this context, one of the main limitations of existing devices is related to the fragility of the biological tissue, which is used as the valve material (chemically treated bovine or porcine tissue). Actually, the crimping process, at low diameter for catheter insertion purpose, and the distortion of the stent once the device is implanted induce specific stress in the leaflets. [4][5][6] Compression at low diameter is particularly interesting for the trans-femoral approach, which requires bringing the valve through the tortuous and already diseased vessel network from an incision in the leg. The advantage of this approach is the need for only light anaesthesia for the patient compared to the trans-apical approach, which requires a mini thoracotomy and a cut in the ventricle apex.Due to the lack of long-term experience with TAVR, today there are only a few results available in the literature that demonstrate the limited durability of biological tissue implanted with the non-invasive pro...