Hydrodynamic function of a biostable polyurethane flexible heart valve after six months in sheep

Survival to six months for sheep with a non-biostable polyurethane mitral h eart valve prosthesis has been reported previously, however, with surface d egradation and accumulation of calcified fibrin/thrombus that impaired leaf let motion and compromised hydrodynamic function. Newly available biostable polyurethanes may overcome this problem. Six adult sheep with biostable polyurethane trileaflet heart valve prosthes es of documented hydrodynamic performance, implanted in the mitral position , were allowed to survive for 6 months. Explanted valves were photographed, resubmitted to hydrodynamic function testing, and studied by light and ele ctron microscopy. Explanted valves were structurally intact and differed little in appearance from their preimplant state. Hydrodynamic testing showed no deterioration in pressure gradient or energy losses compared with pre-implant values. Biostable polyurethanes demonstrated improved blood compatibility leaving l eaflets flexible and valve function unimpaired. Biostable polyurethanes may thus improve prospects for prolonged function of synthetic heart valve pro stheses.