AN IN-VIVO METHOD FOR TESTING HEMOCOMPATIBILITY OF MATERIALS USED IN PROSTHETIC HEART-VALVES

Background and aims of the study: An in vivo method for testing hemoco mpatibility of materials used in mechanical heart valves was developed . Methods: Discs of test materials were glued to specially designed pl astic (Delrin(R)) buttons and implanted into the superior and inferior venae cavae of sheep through a right thoracotomy. The button and disc had such configuration that the blood flow was minimally disturbed. U p to four different materials could be tested simultaneously in each a nimal: two in superior vena cava and two in inferior vena cava. The ma terials and their respective implantation sites were changed between d ifferent animals according to the Latin square principle. Ten animals were used. Three materials currently used in mechanical heart valve pr ostheses - titanium, cobalt-chromium alloy (Haynes 25(R)) and pyrolyti c carbon (Pyrolite(R) - together with a surface modified (methylated) titanium were evaluated. No heparin was given during the experiment. A fter two hours of testing, the discs were explanted and evaluated for hemocampatibility. The thrombus area on each disc was measured with ph otography and planimetry. Platelet and leukocyte adhesion on the surfa ces were quantitatively assessed by scanning electron microscopy (SEM) . The results showed that there were significant differences in thromb us formation (p = 0.001) and leukocyte adhesion (p = 0.002) between th e materials tested. There was no difference between implantation sites bur significant differences between individual animals (p < 0.05). Co nclusion: The results indicate that the method can be used to evaluate early hemocompatibility of biomaterials.