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In atrial fibrillation, erratic electrical impulses in the upper chambers of the heart (atria) cause those chambers to fibrillate, or quiver. This results in an irregular and frequently rapid heart rate. The irregular pattern in the electrocardiogram (EKG, ECG) tracing shows these erratic impulses.
Current as of: May 1, 2026
Author: WebMD Ignite Staff Clinical Review Board All WebMD Ignite education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.
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