Experimental Observation on Antithrombotic Property of A New Bileaflet Mechanical Heart Valve in Sheep

Objective: To observe the antithrombotic property of a new all-pyrolytic car-bon bileaflet mechanical heart valve so as to provide evidence for clinical practice. Meth-ods: 15 sheep underwent mitral valve replacement (MVR) with this new mechanical valve. Each animal was placed on cardiopulmonary bypass. All of the sheep were given in an anticoagulation protocol and followed for three months. Final studies were performed on all animals surviving for more than 12 weeks. Results: 10 sheep died within 48 h after op-eration, 5 sheep survived. The long-term survivors were killed for autopsies,2 sheep were killed after 1 week, 1 after 12 weeks and 2 after two and half years. Pathological examina-tion of 10 sheep which died early after operation revealed that there was neither evidence of thrombosis nor any failure of the mechanical valve. Autopsy studies in the 5 long-term survivors revealed that the sewing ring was covered by a thin layer of microthrombi consis-ted most of platelets and fibrin after 1 week. The sewing ring was covered by a tissue lay-er, with partial organized microthrombi and endothelialization after 12 weeks. Two and half years after operation, the complete endothelialization presented around the sewing ring without restriction of bileaflet motion. The tissue ingrowth tends to stop at the pyrolytic carbon-fabric interface on both surfaces of left atrium and ventricle. This study demonstra-ted that the new prosthetic heart valve had not promoted thrombosis and thrombembolism.