Atrial fibrillation (AF) is one of a number of disorders commonly referred to as arrhythmias ,
in which the heart does not beat with a normal rhythm. AF is caused by a disturbance of
the heart s own electrical system. The problem starts in the upper chambers of the heart
(the atria), and causes these chambers to quiver (or fibrillate ), rather than beat normally.
This can mean that the heart is not pumping as efficiently as it should be.