In Vitro Durability and Stability Testing of a Novel Polymeric Transcatheter Aortic Valve

Abstract

Transcatheter aortic valve replacement (TAVR) has emerged as an effective therapy for the unmet clinical need of inoperable patients with severe aortic stenosis (AS). Current clinically used tissue TAVR valves suffer from limited durability that hampers TAVR’s rapid expansion to younger, lower risk patients. Polymeric TAVR valves optimized for hemodynamic performance, hemocompatibility, extended durability, and resistance to calcific degeneration offer a viable solution to this challenge. We present extensive in vitro durability and stability testing of a novel polymeric TAVR valve (PolyNova valve) using 1) accelerated wear testing (AWT, ISO 5840); 2) calcification susceptibility (in the AWT)—compared with clinically used tissue valves; and 3) extended crimping stability (valves crimped to 16 Fr for 8 days). Hydrodynamic testing was performed every 50M cycles. The valves were also evaluated visually for structural integrity and by scanning electron microscopy for evaluation of surface damage in the micro-scale. Calcium and phosphorus deposition was evaluated using micro-computed tomography (μCT) and inductive coupled plasma spectroscopy. The valves passed 400M cycles in the AWT without failure. The effective orifice area kept stable at 1.8 cm2 with a desired gradual decrease in transvalvular pressure gradient and regurgitation (10.4 mm Hg and 6.9%, respectively). Calcium and phosphorus deposition was significantly lower in the polymeric valve: down by a factor of 85 and 16, respectively—as compared to a tissue valve. Following the extended crimping testing, no tears nor surface damage were evident. The results of this study demonstrate the potential of a polymeric TAVR valve to be a viable alternative to tissue-based TAVR valves.

Transcatheter Heart Valves: A Biomaterials Perspective

“…In vitro hydrodynamic tests show that the polymeric valve outperforms its bioprosthetic counterparts. [ 48,138 ] Moreover, the valve survived 400 m cycles in the accelerated wear testing without failure while maintaining 1.8 cm 2 EOA, 10.4 mmHg ∆P , and 6.9% RF.…”

“…In this process, the polymeric ( x SIBS) pellets are poured into a mold with heat and pressure. [ 48 ] The mold is also connected to a vacuum line to enhance the density and quality of the leaflets. After fabrication, the molded valve was sutured to a laser‐cut nitinol stent.…”

“…However, balloon‐expandable and self‐expandable THVs have been constructed for academic testing and design where the manufacturing details are available. [ 48,188 ] In general, the process of manufacturing stents for THVs consists of precise laser cutting from a cylinder into the metallic frame followed by a polishing and shape setting if the stent is made with nitinol. Shape setting nitinol involves deforming the cylindrical cut stent into its final shape and preventing it from returning while it is heated to a high temperature; the stent is then quenched, which permanently sets its memory shape.…”

“…For instance, the PolyNova valve showed promising durability by maintaining valvular functionality for 400 million cardiac cycles in the fatigue tester. [ 48 ] The in vitro testing is performed in an accelerated wear tester following the ISO 5840 standard. This standard minimum requirement is 200 million cardiac cycles.…”

Transcatheter Aortic Valve Implantation Current Indications and Future Directions

“…Most recently, a glimpse into the future was provided from biomedical engineering with novel and innovative devices consisting of bio-polymeric heart valves. In-vitro testing has shown promising results (60)(61)(62)(63), and it remains to be seen if, and when the technology can be implemented in clinical studies.…”