Development of a reinforced synthetic heart valve for percutaneous delivery

Research output: ThesisDoctoral Thesis

Abstract

Approximately 30% of patients with aortic stenosis over the age of 75 years are refused surgery on the grounds of technical or high risk complications. Following the onset of symptoms, prognosis is very poor if left untreated. Transcatheter aortic valves intervention (TAVI) has paved the way for valve replacement in high risk patients without the need for open heart surgery. The current market approved valves can be delivered percutaneously through the femoral artery or transapically to the beating heart, deployed over the calcified leaflets and begin functioning immediately.
Complications with the current TAVI valves include a requirement for a large delivery sheath which leads to major vascular bleeding. Additionally, these valves use pericardial leaflets, which are too thick to collapse into a small catheter and have a propensity to calcify. It is therefore the objective of this thesis to develop an ultra-thin reinforced synthetic leaflet to reduce the delivery profile and facilitate deployment though a peripheral artery. Polyurethane films reinforced with multi-walled carbon nanotubes were solvent cast and tested for changes to the mechanical properties. Dip coated composite valves with varying content of carbon nanotubes were then developed and tested in a high cycle durability tester.
The stiffness of composites was found to improve overall with increasing nanotube content. However, fatigue life was found to be compromised, with only the 0.125% MWNT-TPU composite material having similar fatigue life to the neat TPU. The durability of the leaflets was also severely compromised when the thickness was dropped below 50 μm. Leaflet stresses were also reportedly highest at the commissures and the belly region. A valve having sufficiently thin leaflets (130 μm) was developed from a harder grade of polyurethane and has survived 23 million cycles to date. It is believed that a thin and durable leaflet can be achieved using harder grades of polyurethanes reinforced with low carbon nanotube concentrations.
Original languageEnglish
Awarding Institution
  • Biomedical Engineering
  • University Of Strathclyde
Supervisors/Advisors
  • Gourlay, Terry, Supervisor
  • Wheatley, David, Supervisor
Place of PublicationGlasgow
Publisher
Publication statusPublished - 2013

Keywords

  • synthetic heart valve
  • aortic stenosis
  • valve replacement

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