Thrombogenicity of polyethylene oxide-bonded dacron sewing ring in a mechanical heart valve

Background and aim of the study: The aim of the study was to evaluate the e ffect of binding hydrophilic polyethylene oxide (PEO) onto Dacron fibers in the sewing ring of a mechanical heart valve (MHV), in terms of thrombogeni city of the prosthesis. Methods: The study was performed in blinded fashion. Six Yorkshire-cross pi gs (bodyweight 35-45 kg) were implanted with MHVs, in the mitral annulus, w ith the PEG-treated sewing ring. An additional five pigs implanted with ide ntical MHVs, hut with untreated sewing rings, served as controls. PEO of ch ain-length 10,000 Da was grafted to Dacron fibers using gamma irradiation. PEG-bonded Dacron fibers (diameter 100 mu m) were Used to weave the sewing ring, which was then assembled on a titanium stent (OD 25 mm). Autologous p latelets were labeled with In-111-tropolone and injected intravenously (850 -1250 mu Ci per injection) into the pigs on removal from cardiopulmonary by pass (CPB). At 20-24 h after surgery, platelet thrombi adherent to MHV comp onents, and shed emboli trapped in the brain, lung, heart, kidneys and othe r organs/connective tissues were imaged using a gamma camera. The animals w ere killed and the amounts of thrombi adherent to MHV components and organ- trapped emboli quantified using an ionization chamber and gamma counter. Results: There was no statistically significant difference in the adhesion of In-111-labeled platelets to either control sewing rings (0.08 +/- 0.06% dose) or PEG-treated rings (0.19 +/- 0.21% dose). The thrombogenicity of MH V components in both animal groups was in the ascending order: Dacron ring > Teflon pledgets > polypropylene sutures > titanium housing > pyrolytic ca rbon. The number of platelet-emboli trapped in the organs was not significa ntly different between the two groups. Conclusions: Simple modifications may not reduce platelet thrombosis or wou nd-healing of the sewing ring in the acute phase, at which time several com plex processes are activating and inactivating platelets and coagulant fact ors during CPB and implantation of MHVs.