Atrial fibrillation, also known as AF, is a form of arrhythmia, also known as an abnormal heartbeat. The abbreviation "afib" refers to this condition. Afib is brought on by abnormally rapid and erratic heartbeats that originate in the upper chambers of the heart (usually more than 400 beats per minute). A regular contraction of the heart muscle is essential to the maintenance of a regular and healthy heartbeat. When at rest, a contraction occurs approximately once per second, but this frequency increases with exercise. The blood is pushed down into the ventricles from the atria, which are the two upper chambers of the heart, with each contraction (the two lower chambers). After that, the ventricles will contract, which will force the blood to either the lungs or the remainder of the body.
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