23-12-2010, 11:54 AM
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ABSTRACT
Artificial pace maker is a one of the modern marvel in the medical science, it is the medical science solution to the electrical problems of a slow or irregular heartbeats. Pace maker is an electronic device that delivers electrical stimulation to the heart to help regulating its beat. Our heart beats because of the natural pacemaker which produce electrical impulses .These impulses cause heart to contract and pump blood and the contraction takes place in a regular intervals .The impulses travel from the pacemaker cells to the muscle walls through some electrical path and cause contraction, generally a normal healthy human heart produces a heartbeat of about 60-100 beats per minute. If there is any interfere with the flow of electrical impulses, this will result in the irregular heartbeats i.e. too slow or two fast heart beats and a complete block of the electrical path. If this occurs contraction of the heart is stopped and blood will not get pumped. In this case a artificial pacemaker is employed in the place of natural pacemaker which works similar to it. Pacemaker is a biomedical device that can regulate the human heart beat when normal mechanism was broken down. Pacemaker is surgically implemented in the chest cavity and has electrodes that are directly in contact with the heart . PACE MAKER IS FOR WHOM? It is for those who are having a A complete block of the heart's electrical pathway. A slow beat. An irregular rhythm.
The heart is composed of atrial and ventricle muscle that makeup the myocardium and specialized fibers that can be sub divided into excitation and conduction fibers. Once electrical activations initiated, contraction of the muscle follows. An orderly sequence of activation of the cardiac muscle in a regularly timed manner is critical for the optimal functioning of the heart. The excitation and conduction system, responsible for the control of the regular pumping of the heart is presented in below Figure .
The first ECG wave within the cardiac cycle is the P-wave, reflecting atrial depolarization. Conduction of the cardiac impulse proceeds from the atria through a series of specialized cardiac structures (the AV node and the His-Purkinje system) to the ventricles. There is a short relatively iso electric segment following the P-wave. This is the PQ interval, which is related to the propagation delay (0.2 s) induced by the AV node. Once the large muscle mass of the ventricles is excited, a rapid and large deflection is observed on the surface ECG. Depolarization of the ventricles is represented by the QRS complex or R-wave. Following the QR complex.
Initial methods employed in electrically stimulating the heart were performed by applying a current that would cause contraction of the muscle tissue of the heart. Albert S. Hyman stated that the introduced electric impulse serves no other purpose than to provide a controllable irritable point from which a wave of excitation may arise normally and sweep over the heart along its accustomed pathways. Hyman designed the first experimental heart pacemaker in 1932 as shown in below.
Wilson Great batch and the cardiologist W.M. Chardack developed the first fully implantable pacemaker. This device was essentially used to treat patients with complete AV block caused by Stokes-Adams diseases, delivering a single-chamber ventricular pacing. It measured 6 cm in diameter and 1.5-cm thick, and the total weight of the pacemaker was approximately 180 g. The pacemaker circuit delivered 1-ms wide pulses to the electrode, a pulse amplitude of 10 mA and a repetition rate of 60 bpm. The average current drain of the circuit under these conditions was about 12 µA, which, energized by ten mercury-zinc cells, gave a continuous operation life estimated at five years.
