ABSTRACT
Blood comes in contact with foreign materials for a short term in extracorporeal devices such as dialysers, blood oxygenators, ventricular assist devices, and catheters. Synthetic vascular grafts implanted as large-vessel replacements have resulted in reasonable degrees of success. The details of the development of heart valve prostheses, design considerations, in vitro functional testing, and durability testing of valve prototypes can be found in several monographs. The initial designs of mechanical valves were of centrally occluding caged ball or caged disc type. The geometry of the valve affords true central flow characteristics with reduced backflow. Accelerated fatigue tests have also shown good wear characteristics for the design and the valve is undergoing further evaluation including animal studies. Most tissues other than bone and cartilage are of the soft category. Non-blood-interfacing soft tissue implants are used to augment or replace natural tissues or to redirect specific biological functions.
