[Development of artificial blood vessel suitable for cerebrovascular surgery: improvement in the mechanical...

Saphenous vein interposition grafts have been commonly used for the reconstruction of occlusive lesions in the extracranial cerebral arteries, such as carotid or vertebral arteries. In contrast, cerebral revascularization using an artificial blood vessel has not been so common. This is due to the fact that conventional artificial blood vessels have been too stiff for use in the cerebrovascular surgery. Another reason is that the patency rate of small-caliber artificial blood vessels has usually been inferior to that found in autologous vein grafts. The purpose of this study was to develop a pliable and compliant artificial blood vessel suitable for the reconstructive cerebrovascular surgery. This new artificial blood vessel is made of polyurethane, porous in structure (porous polyurethane). Thus, multiple small-sized pores exist both in the inner and outer surfaces, and in the wall of the graft. To test its mechanical properties, stress-strain curves and compliance were evaluated. In comparison to expanded polytetrafluoroethylene graft, which has been one of the most commonly used artificial blood vessels in the cardiovascular surgery, the mechanical properties of the porous polyurethane graft more closely resembled those of the common carotid artery in dogs. This means not only that it can be maneuvered with technical ease for anastomosis but also that there is a reduction of compliance mismatch between the host vessel and the artificial vessel. Compliance mismatch has been documented as a major factor in the inducement of intimal hyperplasia, which causes a delayed occlusion of the grafts. In the in vivo animal experiments, a porous polyurethane graft (2.3-3.2 mm in diameter, 40-50 mm in length) was transplanted into the common carotid artery of dogs. The mean size of pore varied from 0 (group 1), 1.7 (group 2), 4.4 (group 3), 5.5 (group 4), 7.4 (group 5), and 30.0 microns (group 6). In the follow-up study conducted 2 months after the transplantation, all grafts in group 4, 5, and 6 were shown to be patent, whereas no patency could be obtained in groups 1, 2 and 3. In addition, all grafts in group 6 were patent 6 months after transplantation, though one showed remarkable stenosis due to anastomotic intimal hyperplasia. Histological examination showed that the luminal surface of the graft was covered with monolayer of endothelium-like cells. Neoadventitia made of collagen developed around the external surface of the graft. Foreign body reactions were minimal. In conclusion, a porous polyurethane graft could be developed, which has improved mechanical properties suitable for the reconstructive surgery of the extracranial cerebral arteries.