PETU-PDMS small-diameter vascular graft experimented as by-pass in the sheep carotid model: functional evaluation and histological results

The ideal arterial substitute should be resistant, easy to suture, biocompatible and should have a non-thrombogenic luminal surface. A prosthetic graft serves adequately as a large vessel substitute, while such a substitute has not yet been found in by-pass applications and reconstructions in lower extremities. A new polyether-urethane (PEtU) elastomeric material based on polydimethylsiloxane (PDMS) was synthesised to realise small-diameter (I.D. 5.O mm) vascular graft: the original idea was to combine into this material the optimal chemical-physical characteristics of polyurethanes with those of biostability and hemocompatibility of silicones (POMS). The hemocompatibility of PEtU-POMS vascular grafts, realized by a peculiar instrument named "spray-machine", was first assessed by in vitro experiments of human blood circulation. Then PEtU-PDMS grafts were implanted both in acute experiments (up to 24 hours), to test the surgical feasibility of by-pass graft technique, and in chronic experiments (up to 2 years) to test the long-tenn perfornlance in the sheep carotid model. The PEtU-POMS grafts were explanted at different time points, cut longitudinally and grossly examined on the luminal side for aneurysm fonnation, thrombosis and anastomotic failure; they were photographed and then processed for histological analysis. The grafts showed the following characteristics: no bleeding and thus no pre-clotting requirement, easy to suture, good elastic properties and mechanical resistance (no kinking or failure were observed), absence of toxicity and calcification, excellent patency and neointima/neoadventitia formation.