Development of an Orthotopic Pulmonary Valve Replacement Porcine Model for Mechanical Heart Valve Thrombosis Research

Abstract Objective Animal models play a vital role in preclinical cardiovascular testing of materials. While sheep have traditionally served as the standard for preclinical cardiovascular testing, pigs are considered a superior option due to a more comparable coagulation system. This study aimed to compare the thrombogenicity of sheep and pigs in a pulmonary valve replacement model. Methods Pigs (n = 12) and sheep (n = 5) underwent pulmonary valve replacement using a bileaflet mechanical valve without any antithrombotic postoperatively. The follow-up period extended to 5 months or until valve thrombosis. Valve performance was evaluated through by cardiac ultrasounds complemented by post-mortem macro- and microscopical analysis of the valve and downstream organs. Results In the pig cohort, terminal valve thrombosis occurred in all but one animal within a month. In the sheep cohort, all animals completed the 5-month follow-up period and post-mortem examination revealed thrombi-free valves with both leaflet mobile. Conclusion Sheep demonstrated insufficient thrombogenicity to induce mechanical valve thrombosis, while pigs exhibited rapid and substantial thrombosis on mechanical valves. These findings support the recommendation to transition to pigs as the standard model for valve thrombosis research.