ABSTRACT
Catheters are fabricated from various polymeric materials, including polyethylene, plasticized polyvinylchloride, polytetrafluoroethylene, Nylon and silicone rubber, as well as from polyurethanes. Polyurethanes have very high flexural endurance compared to most elastomers, making them prime candidates for cardiovascular implants. The insulating material for a pacemaker lead needs to be tough and long-lasting, and provide stable insulation over a long period of time. Thromboresistance is required of a vascular prosthesis to retain graft patency so that thrombi do not form and occlude the vessel or embolize and lodge in a distal site. Endothelial cell seeding of vascular prostheses has been performed to try and promote neointima formation after implantation and complete endothelialization of the luminal surface. The natural heart valves are essentially unidirectional check valves which allow blood flow in one direction.
