On the durability of pyrolytic carbon in vivo.

The durability of pyrolytic carbon heart valve components was examined from the point of view of number implanted, documentation of wear on explanted components, and from the aspect of fatigue. Failures of pyrolytic carbon components were found to be few in number. A model describing the time course of events and successful usage of pyrolytic carbon components in heart valves was developed. The model is based on the yearly shipments of pyrolytic carbon components or valves, starting with 1969. The model indicates that about 2 million components have been successfully implanted, resulting in accumulative experience of over 10 million patient years. The wear of pyrolytic carbon, based on analysis of explanted heart valves, was found to be minimal. Additional wear data obtained on explanted components confirms the earlier observation that wear in vivo in less than that observed in vitro. The recently discovered fatigue behavior of pyrolytic carbon was found to have no demonstrated practical impact on the durability of pyrolytic carbon components used in existing mechanical heart valves.