Artificial Heart Components

In this study, we have attempted to obtain a detailed, quantitative estimate of the surface chemical composition of two commercially available polyurethanes, i.e., Biomer and Avcothane, which have demonstrated a reasonable degree of blood compatibility. For example, Avcothane has been used as an intraaortic balloon pump for post-operative patients (5). Biomer also has been successfully used for artificial heart components in calves (14). 

Stevens. [Stevens Elastomerics] Polyurethane film for headphone ear pads, wheelchair pads, IV xessure infiisers, inflatable splints, artificial heart components, scuba divers buoyancy compensators, diaphragms, cable jacketing, pkg., fabric laminates, adhesive tapes, noise/vibration dampers. 

Thrombotic complications are frequently encountered when blood is exposed to the surfaces of hemodialysis devices, heart-lung machines, arterial grafts, artificial heart components and other prosthetic devices. The blood platelets are particularly vulnerable to these adverse effects which may include a decrease in platelet count, shortened platelet survival and attendant higher platelet turnover, and altered platelet function. However the interaction of platelets with an artificial surface exposed to blood must be preceded by the interaction of the molecular components of plasma, particularly the plasma proteins, with the surface (1,2). This is due to the prepon-... 

Nonlimb Prosthetic Devices. Other prosthetic devices include artificial eyes, breasts, heart valves, and pacemakers. The body s natural heart valve may need to be surgically replaced if it no longer functions properly because of disease, aging, or a birth defect. This vital prosthetic heart component is made from plastic, metal, or pig tissue. Calcification of the prosthetic heart valves is the major cause of product problems, and efforts have been aimed at constructing artificial valves with surfaces that resist calcification. Technological advancements in the durability of the tissue heart valves are also an area of research and could be more applicable to younger patients. 

Materials used in biomedical applications (that is, in intimate contact with living organisms) are called biomateriats. We ll see that a biomaterial must meet many requirements to be suitable for such applications as heart valves, artificial tissue, or hip replacement components. 

One successful total artificial heart is ABIOMED s electric TAH. This artificial heart consists of two seamless blood pumps which assume the roles of the natural heart s two ventricles (Fig. 7). The pumps and valves are fabricated from a polyurethane, Angioflex. Small enough to fit the majority of the adult population, the heart s principal components are implanted in the cavity left by the removal of the diseased natural heart. A modest sized battery pack carried by the patient suppHes power to the drive system. Miniaturized electronics control the artificial heart which mns as smoothly and quietly as the natural heart. Once implanted, the total artificial heart performs the critical function of pumping blood to the entire body (6). 

Wear of medical devices and biomaterials can affect quality of life. Wear of tooth fillings, artificial joints and heart valves can be inconvenient, costly (more frequent replacement) or even life-threateiiiiig (premature breakdowns). Wear of components can also cause accidents. Worn brakes and tires can cause automobile accidents, worn electrical cords can result in electrocution and fires and worn out seals can lead to radiation leaks at nuclear power plants. 

AVE stands for artificial viral envelope [17]. In fact, the lipid components of the AVE liposomes are similar to the HIV envelope and mimic the red blood cell membrane [17]. HVJ-AVE liposomes gave gene expression in liver and muscle that was 5 to 10 times greater than observed with conventional HVJ liposomes [16]. HVJ-AVE liposomes were effective for gene delivery to isolated rat heart by way of the coronary artery. LacZ gene expression was observed in the entire heart, whereas no expression was observed with empty HVJ-AVE liposomes. 

Partial or complete replacement of natural organs with prosthetic components will someday be commonplace. For instance, the design of the total artificial heart, which has had limited clinical success, involved an application of many fundamental principles already discussed as they relate to hemodynamics, biomaterials, and control. Most would agree, however, that the materials-blood-tissue interface is the nidus for some of the most serious problems preventing the development of a safe and reliable artificial heart. This reinforces the importance of investigating at the molecular level the complex interactions that occur between artificial surfaces and the physiological environment. 

That does not exhaust it. On the side of mechanics, the future of IT in everyday life potentially also includes biorobotics (recall that robotics is a current industry term that first appeared in the science fiction novels of Isaac Asimov), and hence more subtle forms of half robotics that mean enhancive replacements of ailing human parts. For many years patients have already been able to have artificial replacement materials, pins, joints, various prosthetics, pacemakers, and artificial hearts. They have also received transplantations and insertions made of natural materials. This trend will doubtless continue to chips and robotic components to restore lost and damaged physiological, neurological and biochemical functions. 

Complex III - Complex III contains a diversity of electron carrying proteins. They include cytochrome b, iron sulfur centers, and cytochrome cl. Cytochrome b is the first of the heme-carrying proteins (Figure 15.6) involved in electron transport. Passage of electrons from cytochrome b to the iron sulfur centers can be blocked by antimycin A. Also, the artificial electron acceptor phenazine methosulfate can accept electrons from cytochrome b and 2,6-dichlorophenol-indophenol can accept electrons from the iron sulfur proteins (Figure 15.9). The crystal structure of the redox components of complex III from bovine heart mitochondria is shown in Figure 15.16... 

Interest in the properties, structure, chemical modification, and application of thin films of organic polymers has grown enormously in recent years. The impetus for this rebirth derives from the relevance of such materials to adhesion (J,), microelectronics (2) lubrication ( ), and biocompatibility (specifically the Interface between living and nonliving components as occurs with Joint replacements or artificial hearts (4.5 ). These materials have also gained increasing importance in the construction of sensors that are based on electrochemical and... 

Development of a drug-loaded nanofibrous material with a slow-releasing antimicrobial agent has significant potential for use in medical devices such as wound dressings, catheter cuffs, repair mesh, prosthetic vascular grafts, sewing cuffs and the artificial heart, all of which have polyester components. 

Central venous catheters, intraaortic balloon pump balloons (polyurethanes), artificial heart bladders (polyurethanes), carrier for drug-delivery coatings, insulators for pacemaker leads, vascular grafts (e.g., biostable polyurethanes), heart-valve components (silicones), extracorporeal tubing... 

Structural components for bioprosthetic heart valves (poly(acetals)], artificial heart housings, catheter components, two-part systems for adhesives (e.g., epoxies)... 

Silicone elastomers have a long history of use in the medical field. They have been applied to cannulas, catheters, drainage tubes, balloon catheters, finger and toe joints, pacemaker lead wire insulation, components of artificial heart valves, breast implants, intraocular lenses, contraceptive devices, burn dressings and a variety of associated medical devices. A silicone reference material has been made available by the National Institutes of Health to equate the blood compatibility of different surfaces for vascular applications. This material is available as a silica-free sheet. Contact the Artificial Heart Program, NHBLI, NIH, Bethesda, Md. for further information. 

Nuclear synthesis became feasible after invention of the cyclotron and the discoveries of neutrons and artificial radioactivity. In early thirties a few artificial radioisotopes of known elements were synthesized. Syntheses of heavier-than-uranium elements were even reported. But physicists just did not dare to take the challenge of the empty boxes at the very heart of the periodic system. It was explained by a variety of reasons but the major one was enormous technical complexity of nuclear synthesis. A chance helped. At the end of 1936 the young Italian physicist E. Segre went for a post-graduate work at Berkley (USA) where one of the first cyclotrons in the world was successfully put into operation. A small component was instrumental in cyclotron operation. It directed a beam of charged accelerated particles to a target. Absorption of a part of the beam led to intense heating of the component so that it had to be made from a refractory material, for instance, molybdenum. 

Polyurethanes have a wide range of applications. Polymers with relatively little cross-linking produce stretchable fibers (Spandex and Lycra) used for bathing suits. Polyurethane foams are used in furniture, mattresses, and car seats and as insulation in portable ice chests. Cross-linked polyurethanes form very tough surface coatings in paints and varnishes. The major component of the Jarvik-7 artificial heart is also a polyurethane. 

DLC deposited on stainless-steel and titanium alloys used for components of artificial heart valves has been found to be biologically and mechanically capable of improving their performance (McHargue, 1991). Devlin etal. (1997) showed improvements to carbon—carbon composite prostheses with DLC coating. 

Prosthetics is the branch of mechcine focused on the replacement of missing body parts with artificial substitutes so that an individual can function and appear more natural. Prostheses are commonly used to replace hands, arms, legs, and feet however, examples of other prosthetic devices developed to improve one s quality of life are heart valves, pacemakers, and components of the ear. Some prosthetic devices, including eye and breast implants, are developed primarily for cosmetic reasons. Several health care professions work together as a team in this process, and teams include a surgeon, a nurse, a prosthetist, and physical and occupational therapists. 

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