Polymer heart valves have been under investigation since the 1960s, but their success has been hampered by an overall lack of durability mainly due to calcification of the leaflets and a relatively high rate of thromboembolic complications. A new polymer (Quatromer) trileaflet design was tested for its thrombogenic potential and was compared to that of existing prosthetic heart valves routinely implanted in patients: a St. Jude Medical bileaflet mechanical heart valve (MHV) and a St. Jude porcine bioprosthetic tissue valve. The valves were mounted in a left ventricular assist device and the procoagulant activity of the platelets was measured using a platelet activation state (PAS) assay. The PAS measurements indicated that the platelet activation level induced by the polymeric valve was very similar to that induced by the St. Jude Medical MHV and the St. Jude tissue valve. No significant difference was observed between the three valves, indicating that they have a comparable thrombogenic potential. Key Words: Thrombogenic-Polymer trileaflet valve-Bioprosthetic tissue valve-Left ventricular assist device-Mechanical heart valve.

A novel polyolefin, poly(styrene-b-isobutylene-b-styrene) (Quatromer), is being proposed as a viable polymer for use in trileaflet heart valves because of its oxidative stability. The current study was designed to assess the polymer's hemocompatibility and mechanical durability. Mechanical characterization included static tensile tests and dynamic tension-tension and bending fatigue tests, where the properties of isotropic and composite (polypropylene (PP) embedded) Quatromer specimens were compared with those of a polyurethane (PUR) approved for cardiovascular applications. It was found that by embedding PP fibers into the Quatromer matrix, the tensile and fatigue properties of the polymer could be improved, making them comparable, if not better than the PUR. The thrombotic potential of Quatromer was compared with the PUR, glutaraldehyde-fixed porcine valve material, and a positive and negative control by measuring platelet deposition with radiolabeled platelets in a parallel plate flow configuration. The porcine valve material was found to have significantly higher platelet deposition under all flow regimes, while no significant difference existed between Quatromer and PUR. In conclusion, Quatromer is shown to have suitable hemocompatibility and mechanical durability for use in polymer trileaflet heart valves, and fiber reinforcement can effectively be used to tailor the mechanical properties.

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Heart valve prostheses have been used successfully since 1960 and generally result in improvement in the longevity and symptomatology of patients with valvular heart disease. However, NIH’s Working Group on Heart Valves reports that 10-year mortality rates still range from 30–55%, and that improvements in valve design are required to minimize thrombotic potential and structural degradation and to improve morbidity and mortality outcomes.

Polymer trileaflet valves have been under investigation for the past 40–50 years in an attempt to produce a valve alternative that is both durable and non-thrombogenic. Most have met with limited success due to oxidative reactions and high dynamic stresses borne by the material [1]. With this knowledge, an oxidatively stable polyolefin, poly(styrene-b-isobutylene-b-styrene) (SIBS), was selected for the design of a fiber-reinforced polymer trileaflet heart valve. The hydrodynamic properties of prototype SIBS valves have been encouraging, but some valves failed prematurely as a result of insufficient durability during in vivo implantation in a sheep model or during accelerated in vitro fatigue.