Atrial fibrillation is a cardiac arrhythmia in which the heart atria (upper chambers) tremble instead of beating effectively in synchronic contraction. Atrial fibrillation can be identified by taking a pulse and observing that the heartbeats do not occur at regular intervals. However, a conclusive indication of atrial fibrillation is the absence of P waves on an electrocardiogram (ECG or EKG), which are normally present when there is a coordinated atrial contraction at the beginning of each heart beat. Risk increases with age, with 8% of people over 80 having AF.
In atrial fibrillation, the normal electrical impulses that are generated by the sinoatrial node are overwhelmed by disorganized electrical impulses that originate in the atria and pulmonary veins, leading to conduction of irregular impulses to the ventricles that generate the heartbeat. The result is an irregular heartbeat which may occur in episodes lasting from minutes to weeks, or it could occur all the time for years. Atrial fibrillation usually becomes a chronic condition, which leads to a small increase in the risk of death. The probability of developing atrial fibrillation increases with age and three to five percent of people over 65 suffer from atrial fibrillation.