Q&A: Roundup on Atrial Fibrillation What is atrial fibrillation?
Atrial fibrillation (sometimes called "a-fib" for short) is a
type of arrhythmia, or irregularity of the heart beat. It
originates in either the left or right atrium, the two upper
pumping chambers of the heart. Normally, the atria fill with
blood returning to the heart. (The right atrium receives blood
from the venous system, and the left from the lungs.) Each
atrium then contracts, propelling this blood into the heart's
two larger, lower chambers, the ventricles. The ventricles
contract and eject this blood—from the right ventricle into the
lungs to be reoxygenated, and from the left ventricle into the
aorta to be circulated through the rest of your body. In atrial
fibrillation, the heart's normal electrical "pacemaker" is
bombarded by competing electrical charges, which originate in
the atria. These competing impulses initiate chaotic muscle
contractions, so instead of contracting forcefully to move the
blood out, the atria quiver or "fibrill