The heart muscle cells generate, conduct and respond to electrical impulses spontaneously. Cardiac contraction is stimulated by impulses from the Sinoatrial node or SA node, which is the pacemaker of the heart, located in the right atrium. Once the SA node stimulates the impulse it travels between the atrium and ventricles, where the Atrioventricular node or AV node is located. Here the impulse stays for a few seconds before it travels to the purkinje fibers and these fibers trigger the ventricles to contract. The electrical activity of the heart is graphed in a wave pattern on an electrocardiogram (ECG/EKG). The electrocardiogram is a test that checks the conduction of the heart and any problems associated with it. It helps locate the cause of chest pain which may be due to inflammation, heart attack or angina. It can help find the cause of symptoms of heart diseases as well as show if medications are working effectively. To understand the pathology on an ECG it is important to know how a normal sinus rhythm works.
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