When an arterial prosthesis is implanted in a patient, the prothesis must maintain a pathway for blood along its entire length. At the present time, the vascular prostheses with a diameter larger than about 6mm are clinically used successfully, but there is continued need for the vascular prostheses with a smaller internal diameter. The major problem is that the thrombogenicity of vascular prostheses frequently limits their clinical usefulness. In developing vascular prostheses, it would be important to understand the mechanisms of thrombus formation and blood coagulation. Also, it would be important to develop new techniques for evaluating antithrombogenicity of artificial materials in vitro prior to implantation. In this paper, the trend in designing and developing the vascular prostheses including hybrid vascular prostheses will be outlined. Also, the mechanisms of blood coagulation and thrombus formation, and functions of endothelial cells will be outlined. A new rheological method to measure the process of coagulation of blood in contact with foreign surface is shown, which will be available for in vitro evaluation of antithrombogenicity of vascular prostheses as well as for elucidating the mechanisms of thrombus formation and blood coagulation.
