CARDIAC PACEMAKER A cardiac pacemaker is an electric stimulator that produces electric pulses that are conducted to electrodes normally located within the lining of the heart (the endocardium). The stimulus conducted to the heart causes it to contract – this effect can be used prosthetically in disease states in which the heart is not stimulated at a proper rate on its own (heart block). Cardiac pacemakers are either of the unipolar or the bipolar type. Unipolar type – a single electrode is in contact with the heart, and the negative-going pulses are connected to it from the generator. Bipolar type – two electrodes are placed within the heart, and the stimulus is applied across theses electrodes.

CARDIAC PACEMAKER PARTS Bundle Branches Purkinje Fibers Electrode Terminal (Front) Electrode Terminal (Rear) Electrode Tip Heart Pacemaker (Pulse Generator) Subclavian Vein

CARDIAC PACEMAKER Asynchronous pacemaker It is the first type of pacemaker that was developed. A cardiac pacemaker that is free running. It gives a fixed heart rate. BLOCK DIAGRAM

CARDIAC PACEMAKER Synchronous pacemaker It is used when a human’s heart can establish a normal cardiac rhythm between periods of block. This means that it is not necessary to stimulates the ventricles continuously. There are two general forms of synchronous pacemakers: the demand pacemaker and the arial-synchronous pacemaker.

CARDIAC PACEMAKER Synchronous pacemaker The demand-type pacemaker BLOCK DIAGRAM

CARDIAC PACEMAKER Synchronous pacemaker The artial-synchronous pacemaker BLOCK DIAGRAM SA – sinoatrial AV – atria to ventricle If the SA anode is able to stimulate the atria, the electrical signal corresponding to atrial contraction can be detected by an electrode. 120ms duration – approximate delay of the AV node