Prostheses Cardiac

Nose, Y., et al., "Development and Evaluation of Cardiac Prostheses", Annual Report, NIH-NHLB NOl-HV-4-2960-5, Cleveland Clinic Foundation, Cleveland, Ohio, 1979. 

This concept is similar to our "Biolization" philosophy, which was proved in the cardiac prostheses. Transient leukopenia in hemodialysis was reviewed from a material blood compatibility point of view. 

Since 1970 biolized materials have been utilized in our cardiac prostheses. Long term survival of TAH (total artificial heart) and LVAD (left ventricular assist device) implanted in animals has shown successful application of these materials without the use of anticoagulants (29). 

Biolized materials have been used in our cardiac prostheses since 1969. The first application utilized glutaraldehyde treated bovine aortic valves in a Dacron fabric pump termed a "partially biolized heart". Since thick pseudoneointima (PNI) formation and calcification was observed, the Dacron covered surface was replaced with natural tissue material (9). This original totally biolized heart was a sac-type with a flexing element of natural rubber lined on the blood side with aldehyde treated bovine pericardium. The outside case of the device was made from polyurethane. Early in 1973, a calf implanted with this artificial heart lived for a then-remarkable seventeen days (10). Termination of the experiment was caused by a crack in the flexing sac. A passive implant of this device in the aorta did not show any thrombus formation during 5.5 years implantation. 

Y. Nose, R. Kiraly, G, Jacobs, C. Arancibia, K. Nakiri, G. Picha, H, Kambic, N. Morinaga, Y, Mitamura, and T. Washizu, "Development and Evaluation of Cardiac Prostheses", Report N01-HV-4-2960-1 (1975)... 

Chronic in vivo hemolysis produces serum lactic dehydrogenase elevations in patients with mitral or atrial valve cardiac prosthesis (J2). In a series of 11 such patients these increases ranged from 1.1 to 1.6 times the upper limit of normal (S29). Blood pH is altered in hemolyzcd specimens because carbonic anhydrase is liberated from the erythrocytes and presumably alters the distribution of H2CO3 and NaHCOs (B2). Hemolysis will effect acid phosphatase activity if the substrate is hydrolyzed by erythrocyte acid phosphatase. Thus, hemolysis would be of concern if phenyl phosphate was the substrate, but would have a negligible effect if )8-glycerophosphate, which is not hydrolyzed by red cell acid phosphatase, was used (Bl). 

Cooley, D., et al., Orthotopic cardiac prosthesis for two-staged cardiac replacement. American Journal of Cardiology, 1969, 24, 123-730. 

For several years, Goodyear supplied their compounded polymer under the name of Hexsyn to various research centers namely, Monsanto Research Corporation ( ), Washington University ( 5), National Bureau of Standards ( 6), Cleveland Clinic (2.) and Thermoelectron Corporation ( 8), These institutions have research programs for physical testing of polymers for use in circulatory assist devices and for the development and evaluation of a cardiac prosthesis funded by the NHLB-NIH. 

Anon., Omnicarbon, Cardiac Valve Prosthesis, Me//ca// c., Inver Grove Heights, Minn. (1993)... 

The most welcome technical achievements in life science are the ones that enhance well-being or restore impaired or lost biological functions. Rehabilitation engineering is a research field that has devoted its full spectrum of efforts to compensate for malfunctions and disorders in human biological systems. This includes the development of devices for the rehabilitation of neural disorders which are termed neural prostheses. Neural prostheses directly interface with the central and peripheral nervous system. The most commonly known neural prosthesis is the cardiac pacemaker, which has existed for more than 30 years. A variety of other lesser known devices have been developed to partially restore neural functions in disabled people. 

Conform to the heart structure rather than the heart structure conforming to the valve (i.e., the size and shape of the prosthesis should not interfere with cardiac function). 

The in vitro study by Dellsperger et al., (16) suggest that at low heart rates and low cardiac outputs the in vivo regurgitation volumes with this prosthesis could become significant. The wall shear stresses created by this valve... 

Cardiac pacemakers Prosthesis implanted to stimulate cardiac muscles to contract. 

S.L. Hilbert, V.J. Ferrans, Y. Tomita, E.E. Eidbo, M. Jones, Evaluation of explanted polyurethane trileaflet cardiac valve prosthesis, J. Thorac. Cardiovasc. Surg. 94 (1987) 419-429. 

The use of bacterial cellulose in medical prosthesis is exciting, considering the perspectives of applications in cardiac bypass surgery and self-transplanted derivation vessels [23]. 

The circulatory fluid is ejected by an electropneumatically driven ventricular pump. Downstream of the pump, an aortic valve assembly is located two different models have been built in order to offer lateral or frontal view of the prosthesis movements. Suitable stent adapters allow to test prostheses of different type and size. The aorta is a variable compliance rubber tube. Through a rigid conduit the fluid is conveyed to the laminar flow assembly which controls peripheral resistances. Aortic compliance and peripheral resistances are hydropneumatically controlled. The fluid, passing through a venous reservoir open to atmospheric pressure, reaches the left atrium. This is a rigid wall chamber in which a hydropneumatic system relates cardiac output to venous return, reproducing Frank--Starling s Law. Between atrium and ventricle there is another valve test assembly which allows to test mitral valves. 

By using a high speed camera it is possible to obtain some films which show the valvular movements in detail. Some frames from a high speed film of the closing phase of the HK prosthesis, 27 mm TAD, are shown in Fig. 3. In this way it is possible to measure the real area of the open valve and to compare it with the nominal area. High speed films are very important for the bioprostheses because their mechanics are not knoxm, a priori. This is the only way to examine the movements of the leaflets during the cardiac cycle. 

C. R. Gentle, The role of simulation studies in cardiac valve prosthesis design, Eng1 in Med., 7 101 (1978). 

Work has been done on fibrous stmctores for aortic valve substitutes, dealing with loose and tight structures to ensure low blood permeability and resistance to high blood pressure gradient [34]. Performance of polyester woven fabrics has been studied by F. Heim for a trileaflets cardiac valve prosthesis (Fig. 13.11), to withstand principal stresses that are distributed in circumferential and longitudinal directions of the loaded leaflets [35]. 

Wisman, C.B., Pierce, W.S., Donachy, J.H., Pae, W.E., Myers, J.L., Prophet, G.A., 1982. A polyurethane trileaflet cardiac valve prosthesis in vitro and in vivo studies. Transactions -American Society for Artificial Internal Organs 28, 164-168. 

Reif, T.H. 1991. A numerical analysis of the back flow between the leaflets of a St. Jude Medical cardiac valve prosthesis. /. Biomech. 24 733-741. 

Implantable medical devices have been widely used to restore body functions, improve the quality of life, or save lives. Experts estimate that 8 to 10 percent of all Americans (some 20 million to 25 million people) [1], or about 1 in 17 people in industrialized countries [2], carry some form of implanted device. Many medical devices, such as the implantable cardiac defibrillator, cochlear implant, artificial vision prosthesis, neuromuscular microstimulator, and the like contain sophisticated electronic circuits. Such long-term implantable medical devices are susceptible to damage by body fluids over time. Hermetic packaging is required to protect the electronic circuitry of the implant from the harsh environment of the human body. 

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