Chapter 6 Materials selection
Abstract Cardiovascular devices have diverse requirements for the materials used in their construction. A range of physical and biological properties must be evaluated along with the materials' processability in order to fabricate an economical, safe, and effective device. The materials used in cardiovascular devices include a broad range of commercially available materials; however, these materials must meet stringent requirements to be acceptable for use in the body. Specifically, these biomaterials include synthetic polymers, biodegradable polymers, biologically derived materials, bioderived macromolecules, passive coatings, bioactive coatings, tissue adhesives, metal alloys, ceramics, and carbons. Applications for these blood-contacting materials include extracorporeal devices, catheters, and tubing devices, which are inserted into a blood vessel, or permanently implanted devices. In the most basic sense, the materials constituting the device, as fabricated and sterilized, must be nontoxic, noncarcinogenic, nonantigenic, and nonmutagenic. Implanted devices impose a new set of requirements, both biologically and from a materials viewpoint. The effect of a foreign body in the cardiovascular system essentially involves the study of thrombosis and wound healing in the presence of a sterile foreign material in flowing blood. The outcome of this healing process can have profound implications for the success of a device and can be dependent on material properties. The durability of the device will be determined by its fatigue resistance and its resistance to biodegradation. Designs will be increasingly scrutinized for durability by regulatory agencies. Each class of biomaterial for cardiovascular applications is categorized by the material properties. The biologic and physical criteria need to be evaluated in the context of the entire device, its application and duration of use, and how it interfaces with the body.