76914608-A-Pacemaker by ajizai


									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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