In atrial fibrillation, erratic electrical impulses in the upper chambers of the heart (atria) cause those chambers to fibrillate, or quiver, resulting in an irregular and frequently rapid heart rate. The irregular pattern in the electrocardiogram (EKG, ECG) tracing shows these erratic impulses.
Last Revised: November 2, 2010
Author: Healthwise Staff
Medical Review: E. Gregory Thompson, MD - Internal Medicine & John M. Miller, MD - Electrophysiology
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