Development of a ceramic heart valve

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A durable, thromboresistant tilting flat disk-type valve was developed. It is comprised of a thin (0.6 mm) single-crystal alumina ceramic disk and titanium nitride housing. The housing was milled from a single piece of titanium and coated with titanium nitride by ion plating.(1) Critical surface tension was 32 dyne/cm for titanium nitride, and 26 dyne/cm for single crystal alumina and LTI carbon. These are nearly equal to the value of 20-30 dyne/cm in which the critical surface tensions of most blood compatible biomaterials range.(2) The single-crystal alumina and titanium nitride showed excellent blood compatibility in vena cava ring tests. Two weeks after implantation one alumina ring showed no thrombi, and the other 4 rings showed a small amount of clot formation at the edges. Three titanium nitride rings showed no thrombi, and the other 2 rings showed a small amount of clot formation at the edges after 2 weeks.(3) Durability testing under high pressure ( up to 1750 mmHg) pulsatile conditions showed that the safety factor appears to be at least 7 times what could be experienced in vivo.(4) Pin on disk wear testings were conducted for measuring the wear rates of the single-crystal crystal alumina and titanium nitride. The wear factor of titanium nitride ( vs single crystal alumina ) was 1.8 X <10^(-7)> <mm^3> /Nm, which would indicate a long life of the valve.(5) The pressure gradient of the ceramic valve was lower than that of the Bjork-Shiley, and nearly equal to those of the Omni-Science and SJM valves. The opening time of the valve disk was measured by optical sensor. The ceramic valve opened most quickly among commercially available valves.(6) The ceramic valve was incorporated into a pneumatic assist pump as an outflow valve and was implanted in 2 sheep. After 5 days, no thrombi were observed on the ceramic valves although a thrombus was found on the conventional valves used as an inflow valve.The ceramic valve is a promising heart valve.