To understand heart rhythm problems, you first need to know how a normal heart works. Your heart is “wired” to beat in a very organized manner. Each side of your heart has two compartments or “chambers.” The top chambers are the atria. The bottom ones are the ventricles. The rhythm of the heart is very organized and controlled by a built-in electrical system running from top to bottom. The SA node, the heart’s own natural pacemaker, signals it to relax and contract in a regular rhythm. Usually your heart rate is regular and beats between 60 and 100 times per minute. When you rest or sleep, it beats more slowly. When you are active, it beats more quickly. The SA node controls all of this. Located in the right atrium (the top right corner of the heart), these special “pacemaker” cells (SA node) send impulses to the AV node. The AV node is located in the center of the heart and acts as a relay between the atria and the ventricles. When the SA node “fires”, the atria contract and an impulse passes to the AV node. Once the impulse passes through the AV node, it travels quickly down through nerve fibers to the bottom of the ventricles. The ventricles contract and squeeze blood out of the heart.
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