Mechanical cardiac valve prostheses: wear characteristics and magnitudes in three bileaflet valves

Three different bileaflet mechanical heart valves were evaluated for wear and durability characterization. The designs of the three mechanical heart valves encompass both geometrical and material interface differences. The St. Jude Medical mechanical heart valve is partially characterized by a flat-on-flat leaflet-to-orifice closing stop interface with the orifice constructed of a graphite substrate with pyrolytic carbon coating. The CarboMedicsTM mechanical heart valve is partially characterized by a flat-on-cylindrical leaflet-to-orifice closing stop interface and the orifice is constructed of solid pyrolytic carbon. The Sorin Biomedica BicarbonTM mechanical heart valve is characterized by a flat-on-flat leaflet-to-orifice closing stop interface with the leaflets constructed of pyrolytic carbon and the orifice constructed of a titanium alloy. In vitro mechanical wear analysis was performed in accordance with current FDA and ISO guidelines for accelerated life and durability testing. Comparisons revealed that the St. Jude Medical mechanical heart valve had the lowest magnitude of wear, but both the St. Jude Medical and CarboMedics mechanical heart valves proved to be very wear resistant. The Sorin Biomedica Bicarbon mechanical heart valve showed an extremely high wear rate and magnitude. The overall mechanism for material removal and wear must be fully determined to assess the long term efficacy of the mechanical heart valve.