Material properties, biocompatibility, and wear resistance of the Medtronic pyrolytic carbon

Pyrolytic carbon is the material of choice for components in the majority of heart valves available today. Many manufacturers have vertically integrated their manufacturing capabilities to include their own carbon manufacturing facilities. Medtronic is no exception. Because of the critical nature of pyrolytic carbon to the success of a valve design, a series of in vitro tests were conducted to determine the relative equivalence of Medtronic and CarboMedics, Inc. (CMI) pyrolytic carbon based on the Medtronic HallTM design. Correlation between in vivo and in vitro pyrolytic carbon wear is provided based on an analysis of explanted Medtronic Hall discs manufactured by CMI. Material, physical, chemical, and biocompatibility proprieties for Medtronic carbon were determined using standardized techniques. Structural integrity of the discs was evaluated by accelerated cyclic testing to determine depth of wear characteristics. Explanted valves were subjected to identical depth of wear analysis. No statistical difference was found between CMI and Medtronic pyrolytic carbon discs based on mechanical and physical properties and depth of wear on both inflow and outflow disc surfaces. Furthermore, evaluation of CMI discs after explant from human subjects confirms similar wear characteristics with a half life in excess of the 570 years projected from the in vitro experiments. In summary, material properties, structural integrity and biocompatibility testing conducted on heart valve discs made by Medtronic showed results virtually identical to those from testing of discs made by CMI.