Serendipity and the development of heparin and carbon surfaces.

In the early 1960s, bileaflet valves fabricated with polymer housings routinely thrombosed within a few hours after implantation in the canine heart. In a serendipitous series of events, the authors found a way to bond heparin to these bileaflet valves using a coating of graphite-carbon and benzalkonium chloride. Over the ensuing 30 years, improved heparin coatings have been developed by other investigators for bonding to various biomedical devices; currently, about 25% of oxygenators used in this country utilize heparin coatings to minimize surface activation of clotting factors. Also, and somewhat serendipitously, a pyrolytic carbon material developed in the 1960s as a coating for nuclear fuel rods was submitted to the authors' laboratory for possible coating with benzalkonium and heparin. This carbon coating, developed at Gulf General Atomic, Inc, would not bond heparin, but it proved to be the best rigid material available for prosthetic valve construction; more than one million pyrolytic carbon valves have been clinically implanted over the last 29 years.