Pacemaker, artificial

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. 

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. 

Many biomedical devices work inside the human body. Pacemakers, artificial heart valves, stents, and even artihcial hearts are some of the bionic devices correcting problems with the cardiovascular system. Pacemakers generate electric signals that improve abnormal heart rates and abnormal heart rhythms. When pulse generators located in the pacemakers sense an abnormal heart rate or rhythm, they produce shocks to restore the normal rate. Stents are inserted into an artery to widen it and open clogged blood vessels. Stents and pacemakers are examples of specialized bionic devices made up of bionic materials compatible with human structure and function. 

DNLM 1. Electrocardiography, Ambulatory—methods. 2. Cardiac Pacing, Artificial. 3. Pacemaker, Artificial. WG 140 H587sm 2004] I. 

Heart Cardiac pacemaker, artificial heart valve, total artificial heart... 

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). 

While it would be difficult to enumerate all of the efforts in the area of implants where plastics are involved, some of the significant ones are (1) the implanted pacemaker, (2) the surgical prosthesis devices to replace lost limbs, (3) the use of plastic tubing to support damaged blood vessels, and (4) the work with the portable artificial kidney. The kidney application illustrates an area where more than the mechanical characteristics of the plastics are used. The kidney machine consists of large areas of a semi-permeable membrane, a cellulosic material in some machines, where the kidney toxins are removed from the body fluids by dialysis based on the semi-permeable characteristics of the plastic membrane. A number of other plastics are continually under study for use in this area, but the basic unit is a device to circulate the body fluid through the dialysis device to separate toxic substances from the blood. The mechanical aspects of the problem are minor but do involve supports for the large amount of membrane required. 

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 only lanthanide of which there is no stable isotope — they all decompose with half-lives between 2.6 and 17.7 years. Strong beta-emitters that are used industrially as thickness gauges. Also suitable as an additive for fluorescent materials. Produced artificially in kg amounts and serves as an energy provider for satellites in radionucleide batteries. Tiny batteries are long-term energy sources for pacemakers. 

Silvery, artificial element generated by beta decay from a plutonium isotope (239Pu). Chemically similar to gadolinium. Like Eu and Gd, Am and Cm are difficult to separate. It can be produced in kilogram amounts. The most common isotope is 244Cm with a half-life of 18.1 years. Is used for thermoelectric nuclide batteries in satellites and pacemakers. It is strongly radioactive and hence also suitable for material analysis. 

Hypersensitivity to amide local anesthetics Stokes-Adams syndrome Wolff-Parkinson-White syndrome severe degrees of sinoatrial, atrioventricular (AV), or intraventricular block in the absence of an artificial pacemaker. 

Uncontrolled CHF cardiogenic shock sinoatrial, AV and intraventricular disorders of impulse generation or conduction (eg, sick sinus node syndrome, AV block) in the absence of an artificial pacemaker bradycardia marked hypotension bronchospastic disorders manifest electrolyte imbalance hypersensitivity to the drug. 

Patients who are hypersensitive to tocainide or to local anesthetics of the amide type should not be exposed to tocainide. The presence of second- or third-degree heart block in the absence of an artificial pacemaker also contraindicates the use of tocainide. 

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]. 

Electrical Stimulation Devices. Bioelectrodes that transmit electrical signals into the body are generally known as electrical stimulation devices, examples of which include cardiac pacemakers, transcutaneous electronic nerve stimulators (TENs) for pain suppression, and neural prostheses such as auditory stimulation systems for the deaf and phrenic nerve stimulators for artificial respiratory control. In these, and other similar devices, electrodes transmit current to appropriate areas of the body for direct control of, or indirect influence over, target cells. 

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). 

In general, a medical device is defined as follows a medical device is an implant and equipment to be used either to achieve disease diagnosis, medical treatment, or disease prevention for human and animals, or to influence the physical structure and function of human and animals. Medical devices for humans may also be classified based on whether and how long the device is in contact with tissue or cells and on the degree of disjunction induced by the device when in a disabling situation. The term covers various categories, such as scissors and tweezers, with small risk to human function, to central venous catheters, artificial dialysis (human kidney), and pacemakers, with high risk to human function. 

Canadian John Hopps invents the first cardiac pacemaker The synthetic fabric, polyester, is invented The first kidney dialysis machine is developed Polyurethanes are synthesized by Otto Baeyer The first plastic artificial eye is developed in the US Percy Spencer creates the first microwave oven... 

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... 

They have also been used in artificial pacemakers for people with heart conditions. The isotope most commonly used for this application is plutonium-238 because the radiation it gives off does not pose a threat to people s health. In spite of the relative safety of the plutonium-238, pacemakers made with other materials are now preferred. 

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