Artificial heart device

Currently, few data are available on the fatigue properties of elastomers cycled at body temperature and in contact with blood. Artificial heart device applications are particularly demanding of elastomers since even a three-year implantation of a heart will involve in excess of 10 cycles. 

Advances in numerous areas have allowed marked increases in survival times of artificial heart device (AHD) and left ventricular assist device (LVAD) experiments. Successful clinical trials employing LVAD s for temporary post-operative assistance after coronary surgical procedures have been reported by several centers (1). As clinical use of circulatory assist devices progresses, longer term (i.e., 3-4 months) implantations will be needed requiring not only initial surface hemocompatibility, but also long-term surface inertness or stability. 

Another challenge in the biomedical materials area is the search for synthetic materials with Improved blood compatibility for artificial heart devices and other organs. An early study by Wade (24) using a series of poly(organophosphazenes) showed these polymers in the unfilled state are as blocompatlble as silicon materials. More recent blood compatibility studies using radiation crossllnked PNF showed excellent hemo compatibility... 

Material surface characteristics are important for cell—material surface interactions. Three types of cell—material surface interactions can be defined, as illustrated in Fig. 7.1, which is based on the concept proposed in Ref. 76. The first one is nonfouling interactions, in which case cells fail to interact with the material surface. This type of interaction is preferred for various biomedical applications such as artificial blood vessels and valves, artificial heart devices, catheters and blood preservation bags. The second type of interactions is passive adhesion, in which case interfacial response is controlled by physicochemical interactions between the material surface, adsorbed proteins and adhering cells. Surfaces in this category inhibit cellular metabolic changes. The adherent cells remain intact and are readily detached from these surfaces with little damage. The third is bioactive cell adhesion, in which cells activate... 

Pusher plate devices Artificial heart devices working with pusher plates moving the blood. 

The isotope plutonium-238 [13981 -16-3] Pu, is of technical importance because of the high heat that accompanies its radioactive decay. This isotope has been and is being used as fuel in small terrestrial and space nuclear-powered sources (3,4). Tu-based radioisotope thermal generator systems dehvered 7 W/kg and cost 120,000/W in 1991 (3). For some time, %Pu was considered to be the most promising power source for the radioisotope-powered artificial heart and for cardiovascular pacemakers. Usage of plutonium was discontinued, however, after it was determined that adequate elimination of penetrating radiation was uncertain (5) (see PROSTHETIC AND BIOMEDICAL devices). 

Economic Aspects. The cardiovascular devices market is estimated to be approximately 2.9 biUion annually on a worldwide basis. This market can be further segmented as follows angiography and angioplasty, 644 x 10 arrhythmia control, 1500 x 10 cardiovascular surgery, 700 x 10 cardiac assist (intra-aortic balloon pump), 80 x 10 and artificial hearts, which are experimental. 

Medicine has made major advances in the past 50 or so years partly by the use of devices to improve patient health. These devices include artificial hearts and pacemakers, machines for artificial kidney dialysis, replacement joints for hips, knees, and fingers, and intraocular lenses. These devices need to survive in sustained contact with blood or living tissue. 

Pretreatment of patients undergoing dental extractions who have implanted prosthetic devices, such as artificial heart valves, to prevent seeding of prosthesis. 

Electrode Assembly. This device consists of a specially machined Teflon electrode holder, two disc electrodes (only one is energized), and a clamp machined from acrylic plastic (Figure 3). The electrode discs are of low-temperature isotropic carbon alloyed with SiC (Carbo-metics, Austin, TX). They were originally developed for use in artificial heart valves (14), and are approximately 1.6 cm in diameter and 1.25 mm thick, and have the surface properties of glassy carbon. Treatment of the discs requires only polishing to a high lustre with diamond grinding compounds of 14,000 and 50,000 mesh. 

Many uses of platinum depend on its chemical inactivity. For example, some people need to have artificial heart pacemakers implanted into their chests. An artificial pacemaker is a device that makes sure the heart beats in a regular pattern. It usually replaces a body part that performs that function but has been damaged. Artificial pacemakers are usually... 

Early attempts to functionalize biomaterial surfaces with biological molecules were focused on improving blood compatibility of cardiovascular devices, such as the artificial heart and synthetic blood vessels, by immobilizing heparin or albumin on polyurethane or Dacron . To enhance cell adhesion to biomaterial surfaces, entire extracellular matrix (ECM) proteins, such as fibronectin and laminin, have been used directly as coatings. However, because of the nonspecific manner of whole protein adsorption, most of the cell binding capability is often lost. Using a molecular templating technique, it may be possible to select which protein(s) to absorb on biomaterial surfaces. ... 

Medical devices can be anything from thermometers to artificial hearts to in-home pregnancy test kits. Devices, unlike drugs, are not dependent on a chemical action. Device inventors are more concerned with anatomy—skin, internal organs, tissue—and the compatibility of the device both within and on the surface of the body. 

The artificial heart has the greatest power requirements for implanted devices, exceeding 10 W there are no acceptable implantable batteries for this application at present. 

In-Vivo Percutaneous Implant Experiment. The principle of percutaneous attachment has extensive application in many biomedical areas, including the attachment of dental and orthopedic prostheses directly to skeletal structures, external attachment for cardiac pacer leads, neuromuscular electrodes, energy transmission to artificial heart and for hemodialysis. Several attempts to solve the problem of fixation and stabilization of percutaneous implants(19) have been made. Failures were also attributed to the inability of the soft tissue interface to form an anatomic seal and a barrier to bacteria. In the current studies, the effect of pore size on soft tissue ingrowth and attachment to porous polyurethane (PU) surface and the effect of the flange to stem ratio and biomechanical compliance on the fixation and stabilization of the percutaneous devices have been investigated.(20)... 

Polyurethane (PEU) Artificial hearts and ventricular assist devices Catheters Pacemaker leads... 

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-... 

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