Investigation of three‐surface properties of several metals and their relation to blood compatibility

Organic‐free specimens of 5 metals were prepared and characterized by parameters indicating their relative surface charge, surface texture, and surface energy prior to evaluation of their degree of thromboresistance. For the materials studied, there was no predictive correlation between the pre‐implatation electrical rest potentials and ultimate thromboresistance when standard prosthetic rings were placed in the canine inferior vena cava. Surface textural inhomogeneities greater thatn a micrometer or so made thrombus formation a certainty. There was a positive postimplantation correlation between the presence of a thin, labile, proteinaceous deposit on the prosthetic ring lumens and the passivation of the “high‐energy” materials towards thrombus accumulation. The metals which did consistently passivate, 316 Stainless Steel and Stellite 21, did so dynamically by acquiring an organic film within 2 hr after implantation. During continued residence in fresh, flowing blood these metals ultimately became dominated by an apparently monodisperse protein component of low critical surface tension. These findings were confirmed when thromboresistant pyrolytic carbon having initial surface properties similar to the metals but lacking reactivity and corrosivity was used as a comparison standard.