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A pacemaker (or artificial pacemaker, so as not to be confused with the heart's natural pacemaker) is a medical device that uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart. The primary purpose of a pacemaker is to maintain an adequate heart rate, either because of the heart's native pacemaker is not fast enough, or there is a block in the heart's electrical conduction system. Modern pacemakers are externally programmable and allow the cardiologist to select the optimum pacing modes for individual patients. Some combine a pacemaker and defibrillator in a single implantable device. Others have multiple electrodes stimulating differing positions within the heart to improve synchronisation of the lower chambers of the heart. pacemaker, artificial, device used to stimulate a rhythmic heartbeat by means of electrical impulses. Implanted in the body when the heart's own electrical conduction system (natural pacemaker) does not function normally, the battery-powered device emits impulses that trigger heart-muscle contraction at a rate that is preset or is determined by demand. The device today may be as small as one inch (2.5 cm) in diameter and weigh as little as 0.5 oz. (14 gm). It is implanted, using local anesthetic, under a flap of skin in the chest or abdomen. Pacemakers are sophisticated electronic devices. Therefore, some manufacturers rely on outside suppliers to provide many of the component parts. The construction of a pacemaker is not a linear process but an integrated one. Component parts such as the battery, leads, and the circuitry are constructed individually, then pieced together to form the final product. Making the battery 1 The primary type of battery used in pacemakers is a lithium/iodine cell. One method used by manufacturers to make these batteries involves first mixing together the iodine and a polymer such as poly2-vinylpyridine (PVP). They are heated together, forming a molten charge-transfer complex. This liquid is then poured into a half moon-shaped, preformed cell which contains the other components of the battery, including the lithium anode (positive charge) and a cathode collector screen. The iodine/polymer blend solidifies as it cools to form the cathode. After the cathode is formed, the battery is hermetically sealed to prevent moisture from entering. Making the leads 2 The leads are typically composed of a metal alloy. The wire is made by an extrusion process in which the metal is heated until it is molten, then pushed through an appropriately sized opening. It is cut, then bundled with many other wires and treated with a polymeric insulator such as polyurethane. One end of the lead wires is fashioned with a shaped tip, and the other is fitted with a pacemaker connector. Making the motherboard 3 The motherboard contains all the electrical circuitry of the pacemaker, including Final assembly and packaging 4 When all of the component pieces are available, final assembly takes place. The circuitry is connected to the battery, and both are inserted into the metal casing. The casing used for a pacemaker is typically formed using titanium or a titanium alloy. It is constructed in multiple pieces that are sealed together after the other pacemaker components are introduced. A fitting is also affixed to the casing, providing a connecting point for the leads. 5 The finished devices are then put into final packaging along with accessories. After being exhaustively tested, they are then sent out to distributors and finally to doctors.
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