Problems of materials in mechanical heart systems

Abstract

SummaryCiirrently available materials for mechanical heart systems are surveyed, particularly m-ith respect, to long-term implantation, from the viewpoints of availability and workability, mechanical and biological durability, and compatibilit'y with blood and tissue. Some materials have one or more desirable physical properties, btit none offers perfect blood and tissue compatibility. Medical grade Silastic, considered best, for blood handling parts, has produced promising results in auxiliary ventricle patency exneriments. The insufficient tensile stiength of Silastic should be increased, and it may be possible to accomplish this while maintaining the present resilience, elongation, and inertness. No long-term data on thrombus formation are available, but clot-retarding quality is essential and may perhaps be obtained by incorporating heparin. Developments in polymer chemistry may also lead to other surfaces with the requisite mechanical properties with blood.

The Biocompatibility Challenges in the Total Artificial Heart Evolution

“…Most materials were borrowed from the mechanical industry and, therefore, were not suitable for medical purposes, which required contact with one of the most hostile and aggressive environments (i.e., the human body). Furthermore, few aspects of TAHs' mechanical behavior and biological stability were known or tested, even though the fundamental requirements had already been identified (114,115).…”

An introduction to blood compatible polymer surfaces for use in artificial internal organs

“…While the foregoing is intended to show that tissuepolymer interactions are indeed a problem, materials such as Dacron@ and Mylar@ ( DuPont polyethylene terephthalate ) , Silasticn ( Dow Corning polydimethylsiloxane), and Teflon@ ( DuPont polytetrafluoroethylene ) are nevertheless sufficiently resistive to be considered for use in mechanical heart systems ( 8 ) .…”

“…A nonthrombogenic surface suitable for all applications is still in the future. For further information on the topics discussed here the reader is referred to several related articles on the theories of blood coagulation (59), of the effects of implants on blood (60), surface activity in blood coagulation (61), biomedical polymers (62, 6 3 ) , materials in mechanical heart systems (8) and artificial organs (64), thrombus formation on polymeric materials (53), and the mechanical surface and gas layer effects on moving blood (65). For original research articles the reader is referred to the .lournu1 of Biomedical Materials Research and the Transactions of the American Society for Artificial Internal Organs.…”

Purchase specifications for biomedical materials. I. Sheet or film of polytetrafluoroethylene plastic

“…The polymer has a long and generally successful history of clinical application. [1][2][3][4][5] This class of polymer is available to the clinician in a variety of forms; homogeneous sheet or film, woven and nonwoven fabric, monofilamentary and braided fiber, arid knitted fabric are examples.…”