Heart artificial pacemaker

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... 

Industry and Business Sectors. The pharmaceutical industry, along with the medical equipment industry, employs biomedical engineers. The medical industry, including the supphers of laboratory equij>-ment, imaging technology, bionics, and pharmaceuticals, drives much of the employment demand for biomedical engineers. Medical hardware, such as artificial hearts, pacemakers, and renal dialysis machines, remains an important part of biomedical engineering employment. 

Biomaterials have played a vital role in the treatment of cardiovascular diseases, examples of applications including heart valve prostheses, vascular grafts, stents, indwelling catheters, ventricular assist devices, total implantable artificial heart, pacemakers, automatic internal cardioverter defibrillator, intraaortic balloon pump, and more. A key requirement for materials in cardiovascular applications, particularly blood-contacting devices, is blood compatibility, that is, nonthrombogenic. Additional requirements include mechanical and surface properties that are application specific. Surveying the field of polymers used in cardiovascular applications reveals that PUs, polyethylene terephthalate (PET), and expanded PTFE (ePTFE) are the most commonly used. This section will review each of the three polymers followed by a brief introduction of other emerging polymers for use in the cardiovascular area. 

On the other hand, poly(ether urethone)s should be more stable and applications have been seen in the artificial heart, pacemaker leads, flexible leaflet heart valves and catheters. Whilst success appears to have been achieved in several of these situations, it is clear that stability cannot be guaranteed and several problems have arisen. 

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). 

Polymers are a fundamental part of the modem world, showing up in everything from coffee cups to cars to clothing. In medicine, too, their importance is growing for purposes as diverse as cardiac pacemakers, artificial heart valves, and biodegradable sutures. 

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. 

The most widely studied synthetic polymers for blood contact applications are polyether urethane ureas ( Biomer (Ethicon)). These materials have been used in artificial hearts, as coatings for lead wires in pacemakers, have been used and are being considered for blood vessel prostheses. The success of these materials is believed to be due to preferential adsorption of albumin rather than globulin or fibrinogen which promote a clotting response. However, these materials are hydrophobic and questions of long-term effectiveness are unresolved. Particularly, these materials may shed emboli or may be susceptible to surface calcification. Thus, it may be desirable to have synthetic polymers which are hydrophilic and better resemble blood vessels [475]. 

There are several other commercial products containing segmented polyurethane (SPU) such as pellethane or cardiothane. These SPUs are widely recognized to possess notable biomedical properties as materials for artificial heart and intra-aortic balloon pumping (IABP), and also as coating materials for pacemaker-lead insulators (See Sect. 4.1). 

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. 

Tocainide does not change heart rate or blood pressure. Tocainide is contraindicated in patients with second- or third-degree AV block in the absence of an artificial ventricular pacemaker. 

Isoproterenol (ISUPREL, others) may be used in emergencies to stimulate heart rate in patients with bradycardia or heart block, particularly in anticipation of inserting ait artificial cardiac pacemaker or in patients with the ventricular arrhythmia torsades de pointes. In asthma and shock isoproterenol largely has been replaced by other sympathomimetic drugs (set below and Chapter 27). 

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

The low penetrating radiation, long half-life, and high power density of Pu makes it ideal for special purpose power supplies ( 6.9.3). The main present use is in space research, and 30 kW power sources have been launched into space, Pu has been used in heart pacemakers and is still a candidate as a power source for completely artificial hearts. Production of Pu requires the isolation of Np, which is then irradiated and reprocessed to produce pure Pu. 

Other cardiovascular uses have included coatings on pacemakers and pacemaker lead-wires for purposes of insulation and for achieving biocompatibility. Medical grade silicone elastomer has been widely used as a material of construction in experimental artificial hearts and heart assist devices. Silicone tubing is often preferred for use in roller-type blood pumps during cardiopulmonary bypass. Medical grade silicone elastomer contains no leachable or organic plasticizers and thus contributes minimal contamination in blood contact applications. 

Current introduced to the body is often held to low values by the electrical resistance of dry skin, between 5,000 and 10,000 ohms (Kantrowitz, 1972). Wet skin will have electrical resistance levels as low as one-tenth of this. Where electrical leads are introduced subcutaneously, resistance falls to 10-50 ohms, and this situation is potentially dangerous. Subcutaneous leads are used for heart pacemakers, artificial hearts, transcutaneous electrical neural stimulation (TENS) to block pain, and subdural leads for the control of Parkinson s disease. 

Vascular grafts and patches, as well as heart valves, are among the oldest of cardiovascular implants. More recently, permanent internal devices include pacemakers, defibrillators, stents, left ventricular assist devices, and artificial hearts. 

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... 

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