Pacemakers cardiac

Cardiac Pacemakers and Mechanical Hearts—-A. Bibliography of Radioisotope Power Sources, TID-3336, Technical Information Center, U.S. Atomic Energy Commission, Washington, D.C., 1973. 

Worldwide, more than 250,000 cardiac pacemakers were implanted in 1995, accounting for well in excess of 1 biUion in sales. It is estimated that over 500,000 people in the United States alone have pacemakers. Millions of people have been able to lead normal lives thanks to this remarkable device. 

Because normal radioisotopic decay lowers the thermal output by about 2.5%/yr in these units, they are purposefully overdesigned for beginning of life conditions. Several of these generators have successfully operated for as long as 28 years. This is approximately equal to the half-life of the strontium-90 isotope used in the heat sources. The original SNAP-7 series immobilized the strontium-90 as the titanate, but the more recent ones have used it in the form of the fluoride, which is also very stable. A number of tiny nuclear-powered cardiac pacemaker batteries were developed, which have electrical power outputs of 33—600 p.W and have been proven in use (17). 

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. 

Bamscotti M, Bucchi A, Di Francesco D (2005) Physiology and pharmacology of the cardiac pacemaker ( fimny ) current. Pharmacol Ther 107 59-79... 

Furthermore, pH determination has been used in other clinical research, both alone and in combination with other measurements. This research includes studies into the relationship between extracellular and intracellular pH in an ischemic heart [6, 7], the pH of airway lining fluid in respiratory disease [8], the study of pH as a marker for pyloric stenosis [9], malnutrition in alkalotic peritoneal dialysis patients [10], pH modulation of heterosexual HIV transmission [11, 12], and wound prevention and treatment [13], In addition, pH changes due to blood acidosis have been used to trigger and pace the ventricular rate of an implanted cardiac pacemaker [14], Research using pH measurements... 

Lithium iodide is the electrolyte in a number of specialist batteries, especially in implanted cardiac pacemakers. In this battery the anode is made of lithium metal. A conducting polymer of iodine and poly-2-vinyl pyridine (P2VP) is employed as cathode because iodine itself is not a good enough electronic conductor (Fig. 2.3a). The cell is fabricated by placing the Li anode in contact with the polyvinyl pyridine-iodine polymer. The lithium, being a reactive metal, immediately combines with the iodine in the polymer to form a thin layer of lithium iodide, Lil, which acts as the electrolyte ... 

Cardiac pacemaker lead with steroid-coated tip. 

General definitions relating to action potentials are given in Section 9. This section deals specifically with action potentials within the cardiac pacemaker cells and conducting system. 

You will be expected to have an understanding of action potentials in nerves, cardiac pacemaker cells and cardiac conduction pathways. 

Mexiletine is contraindicated in the presence of cardiogenic shock or preexisting second- or third-degree heart block in the absence of a cardiac pacemaker. Caution must be exercised in administration of the drug to patients with sinus node dysfunction or disturbances of intraventricular conduction. 

Their antihypertensive efficacy is comparable to that of (3-adrenergic blockers and angiotensin-converting enzyme (ACE) inhibitors. The choice of a calcium channel blocker, especially for combination therapy, is largely influenced by the effect of the drug on cardiac pacemakers and contractility and coexisting diseases, such as angina, asthma, and peripheral vascular disease. 

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. 

Much of the recent research in solid state chemistry is related to the ionic conductivity properties of solids, and new electrochemical cells and devices are being developed that contain solid, instead of liquid, electrolytes. Solid-state batteries are potentially useful because they can perform over a wide temperature range, they have a long shelf life, it is possible to make them very small, and they are spill-proof We use batteries all the time—to start cars, in toys, watches, cardiac pacemakers, and so on. Increasingly we need lightweight, small but powerful batteries for a variety of uses such as computer memory chips, laptop computers, and mobile phones. Once a primary battery has discharged, the reaction cannot be reversed and it has to be thrown away, so there is also interest in solid electrolytes in the production of secondary or storage batteries, which are reversible because once the chemical reaction has taken place the reactant concentrations can be... 

The cardiovascular effects of local anesthetics result in part from direct effects of these drugs on the cardiac and smooth muscle membranes and from indirect effects on the autonomic nervous system. As described in Chapter 14, local anesthetics block cardiac sodium channels and thus depress abnormal cardiac pacemaker activity, excitability, and conduction. At extremely high concentrations, local anesthetics can also block calcium channels. With the notable exception of cocaine, local anesthetics also depress myocardial contractility and produce direct arteriolar dilation, leading to systemic hypotension. Cardiovascular collapse is rare, but has been reported after large doses of bupivacaine and ropivacaine have been inadvertently administered into the intravascular space. 

Coagulation is not the only problem with materials intended for implantation, however. Cardiac pacemakers are intended to correct arrhythmias. Insulating materials for a pacemaker lead must be tough and long lasting. The first leads were insulated with polyethylene or silicone rubber. Neither material was considered ideal because of endocardial reactions (polyethylene) and limited durability (silicone rubber). The strength and flexibility of polyurethanes led to their introduction in 1978 as lead insulators. 

An exploded view of a rectangular cardiac pacemaker cell which was produced by SAFT is given in Fig. 4.16. 

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