Demand pacemakers

Wolff-Parkinson-White syndrome In several cases, the tachycardia was replaced by a severe bradycardia requiring a demand pacemaker after propranolol administration with as little as 5 mg. 

Demand pacemakers are very low current devices, requiring only 25-50 jiW for sensing and 60-100 pW for stimulation. In contrast, implanted ventricular defibrillators (Fig. 1.3) must be able to deliver short electric pulses of 25-40 J (e.g. 2 A at 2 V for 10 s) which can shock the heart into normal rhythm, and hence require a much higher rate battery. The most common system is a lithium-silver vanadium oxide cell with a liquid-organic based electrolyte. More than 80 000 such units have been implanted. Implanted drug delivery devices also use lithium primary batteries, as do neurostimulators and bone growth stimulators. 

Mymin D, Cuddy TE, Sinha SN, et al. Inhibition of demand pacemakers by skeletal muscle potentials. JAMA 1973 223 527—532. 

Barold SS, Ong LS, Ealkoff MD, Henle RA. Inhibition of bipolar demand pacemaker by diaphragmatic myopotentials. Circulation 1977 56 679-683. 

Gialafus J, MaUlis A, Kalogeropoulos C, Kalikazaros J, Basiakos L, Avqoustakis D. Inhibition of demand pacemakers by myopotentials. Am Heart J 1985 109 984. 

The demand for electrically operated tools or devices that can be handled independently of stationary power sources led to a variety of different battery systems which are chosen depending on the field of application. In the case of rare usage, e.g., for household electric torches or for long-term applications with low current consumption, such as watches or heart pacemakers, primary cells (zinc-carbon, alkaline-manganese or lithium-iodide cells) are chosen. For many applications such as starter batteries in cars, only rechargeable battery systems, e.g., lead accumulators, are reasonable with regard to costs and the environment. 

Ivabradine Investigational inhibitor of sinoatrial pacemaker reduction of heart rate reduces oxygen demand ... 

Many articles have been written on the demand for implants. It is difficult to estimate the market. The most popular implants are likely to be hip, knee, finger, dental root, heart valve, pacemakers and jaw reinforcement. Worldwide the demand is 100,000 heart valves, 220,000 pacemakers, 400,000 hip prostheses and 1,500,000 blood vessel prostheses. 

Demand pacing—type of pacemaker that responds to the needs of the body rather than uniformly pacing heartbeats at a single rate. Ventricles—The two lower chambers of the heart also the main pumping chambers. 

The overall performance and reliability of both implanted and external medical devices depend strongly on the battery characteristics (including chemical composition of the electrodes as well as the battery design and electrolyte). Lithium-based batteries are the current choice for pacemakers, where continuous power requirements are on the order of 10"4 W battery duration depends on demand factors and is about 7 years for continuous service (16). Other devices are being developed that have higher power needs and serve specialty markets (probably smaller than that for pacemakers). Some of these are the following ... 

The fourth position represents rate modulation. Rate modulation is the ability of the pacemaker to adjust the timing events according to signals from a sensor. Sensors such as motion, acceleration, temperature, or impedance may be used to adjust the pacing rate to the physical activity or metabohc demands of the patient. 

The monitoring requirements for endocardial lead extraction are somewhat more demanding than those for a permanent pacemaker procedure. In addition to reliable electrocardiographic monitoring, it is recommended that intra-arterial monitoring also be carried out. This helps to readily detect any sudden change or drop in blood pressure caused by a vascular tear or tamponade. 

Due to the increase in human life expectancy, an increasing and constant demand for biomaterials has developed. Ini993 in the United States alone, approximately 1.4 milhon cataract patients were treated and fitted with intraocular lenses. In the area of cardiovascular surgery 250,000 pacemakers and 120,000 heart valves are implanted yearly worldwide [5]. 

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. 

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