Atrial fibrillation is an arrhythmia confined to the atria and characterized by extremely rapid, irregular, and ineffective atrial contractions. Atrial fibrillation can be caused by a number of factors, including continuously reactivating reentrant electrical circuits and repetitively activating areas that initiate electrial waves at rapid rates.
During atrial flutter or atrial tachycardia, the ventricles do not beat as rapidly as the atria because the conduction delay between the atria and ventricles prevents many atrial bioelectrical waves from reaching the ventricles. Despite compromised atrial contraction, this type of arrhythmia usually is not immediately life-threatening. However, it can lead to other problems, such as chronic fatigue, congestive heart failure, and increased risk of stroke.
About 2.2 million Americans have atrial fibrillation. The likelihood of developing atrial fibrillation increases with age. Three to five percent of adults over 65 have atrial fibrillation.