Replacement heart valves offer substantial benefits to the patients with severe valvular heart disease. However, current prosthetic heart valves are still unable to meet the needs for more durable tissue valves and less thrombogenic mechanical valves. The aim of this research was to develop and evaluate a new generation heart valves made from a new shape-memory nitinol scaffold and a novel nanocomposite material known as polyhedral oligomeric silsesquioxanes poly(carbonateāurea) urethane (POSS-PCU). During the course of this research, the biomechanical properties of POSS-PCU nanocomposite were evaluated and compared to those of the materials currently used to fabricate bioprosthetic valves. Moreover, POSS-PCU nanocomposite was chemically engineered to improve its oxidative stability and minimise biodegradation. A novel artificial aortic valve was devised and transferred from a stented design into a semi-stented concept and then a retrievable and repositionable valve suitable for transcatheter implantation. The proposed surgical and transcatheter valves were manufactured by an innovative automated dip-coating technique. An industrial-scale automated dipping mechanism was designed to improve the reproducibility of polymeric valve leaflets with no need to suturing or adhesives. The POSS-PCU valves were assessed in vitro for their hydrodynamic performance in a test setup complying with ISO 5840 standards and were shown to have an advanced function compared to clinically available prosthetic valves. The transcatheter POSS-PCU valves (Triskele valves) were then subjected to preliminary acute animal study in ovine model and successfully implanted, retrieved and repositioned in orthotopic position with excellent valve function. The promising results from the in vitro functional tests and the preliminary in vivo study encourage the use of POSS-PCU nanocomposite material and superelastic nitinol wire-frame to develop a new generation transcatheter heart valves which can overcome the main limitations experienced with current solutions. Although further durability and long-term animal studies are required which are currently under investigation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:639657 |
| Date | January 2015 |
| Creators | Rahmani, B. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1460756/ |
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