Five polyurethane vascular grafts with three different chemistries were investigated in terms of device function, healing characteristics and material stability in a canine abdominal aorta model for prescheduled periods of 1 and 6 months. Corvita-reinforced grafts, with walls made of poly(carbonate urethane) (PCU) filaments, displayed a relatively thin, uniform and partially endothelialized inner capsule with good tissue in-growth. The external polyester mesh separated from the underlying PCU wall due to the degradation of the melt adhesive between these two layers. Three types of Thoratec access graft exhibited a high degree of thrombus and little tissue in-growth, and were non-adhesive to both the inner and external capsules as the solid layer beneath their lumens completely blocked any transmural communication. The microporous poly(ether urethane urea) degraded extensively. Pulse-Tec grafts at one month also demonstrated non-adhesive properties because the external skin served as a barrier to tissue in-growth. At 6 months, its poly(ether urethane) wall displayed the most severe degradation, damaging graft structural integrity and causing significant tissue deposition in the degradation areas. This study shows the importance of multiple factors in vascular prosthesis design and demonstrates that collective and comprehensive thinking will be key in the future development of creative and novel approaches.

Three polyurethane (PU) vascular grafts with novel designs were investigated and compared in terms of the microporous structure, reinforcement technology, polymer chemistry, microphase separation, and mechanical properties. The Corvita graft, composed of a poly(carbonate urethane) polymer, displayed a helically wound filament structure with communicating inter-fiber spaces. The reinforced model contained an external PET mesh impregnated with a protein sealant, and displayed good microphase separation, the highest Young's modulus in the longitudinal direction, and the second highest in the radial direction. The Thoratec graft was made of a polyetherurethaneurea with an average micropore size of 15 microns. Silicone was observed on both surfaces of the graft. The Thoratec device displayed a low degree of hydrogen-bonding among the urethane groups and had no well-organized hard-segment domains. Its mechanical strength was superior to that of the Pulse-Tec graft. A solid PU layer underneath the luminal surface precluded any communication between the luminal and adventitial sides. The Pulse-Tec prosthesis was composed of polyetherurethane, with an average micropore size of 28 microns. It offered the highest radial compliance, a high degree of hydrogen-bonding, a narrow molecular weight distribution, and a certain degree of microphase separation. Its tensile strength and hysteresis loss were inferior to those of the other two grafts.