Atrial fibrillation, or AFib, is a heart arrhythmia that occurs when disorganized electrical signals in the heart cause the heart's upper chambers to contract quickly and irregularly. AFib increases the risk of stroke, and in some people may cause chest pain or heart failure, reports the National Institutes of Health.
In a healthy human heart, electrical signals travel from the top of the heart to the bottom, and as these signals travel they cause the heart to contract and pump blood. An electrical signal to begin a new heartbeat occurs 60 to 100 times a minute. With AFib, electrical signals do not begin in the right atrium but in another part of the atria or in nearby pulmonary veins, and the subsequent electrical signal does not occur in its typical, coordinated manner. AFib may produce heartbeats of 100 to 175 beats per minute, states NIH.
When blood does not pump efficiently from the atria to the ventricles, blood may pool or form clots. Stroke may occur when one of these clots breaks off and clogs an artery in the brain, and a person with AFib is five times as likely to have a stroke. Additionally, AFib impedes the heart's ability to pump blood, which in turn increases the risk of heart failure, says WebMD.