On-X Carbon Cardiovascular Applications
Pyrolytic carbon was originally developed for the nuclear power industry in the 1960's. It is created by heating a hydrocarbon gas to release carbon atoms onto a solid substrate material. Under the right conditions a uniform, isotropic carbon coating is formed exhibiting high strength and durability.
For more than thirty years, mechanical heart valve manufacturers have used pyrolytic carbon in valve construction. Because of deficiencies in process control, these pyrolytic carbons had to be alloyed with silicon carbide to ensure needed wear resistance. Silicon carbide, however, compromises biocompatibility and material properties.
In the early 1990’s, On-X LTI (formerly MCRI) developed a sophisticated closed loop process control technology for pyrolytic carbon coating to replace the open loop process controls typically used. This breakthrough made it possible to produce a wear resistant pyrolytic carbon without the silicon alloying element. This new form of pure pyrolytic carbon was called On-X carbon and offers the following advantages over other pyrolytic carbons:
- Less thrombogenic
- Better surface finish
- 25% greater fracture strength
- 50% greater toughness
On-X LTI’s On-X Prosthetic Heart Valve utilizes On-X carbon. Its innovative design along with the thromboresistant surface of On-X carbon is yielding outstanding clinical results. It is the first mechanical valve to receive FDA approval to conduct low dose anti-coagulation studies.
The outstanding blood compatibility of On-X carbon together with its biostability and wear resistance makes it ideal for the construction of heart valve prostheses and components used in artificial hearts and cardiac assist devices. Other cardiovascular applications include vessel connectors, ducts for special blood handling devices and percutaneous access ports.
On-X carbon is a structural carbon coating that is most often deposited on a graphite substrate pre-form. Alternatively for some geometries, deposition techniques can be employed to produce components of solid On-X carbon. Required thickness of the deposited carbon depends on the design requirements of the product. The surface can be polished to a high gloss where articulation or thromboresistance is required. The surface can also be left in an as deposited state providing some surface topography for bone and or tissue on-growth.