Atrial Fibrillation occurs when stray electrical pulses disrupt the muscle contractions of the heart which can intrupt the regular, coordinated top-to-bottom pumping action in the atria. These fibrillations do not allow for the proper pumping of blood into the heart's lower chambers, the ventricals, and there is lower output of oxginatied blood to the body.
Until recently Doctors viewed this atrial fibrillation as benign, or not a cause of worry. The palpitations, dizziness and shortness of breath that patients experienced seemed to go away after a short while. It is now understood that atrial fibrillation allows blood to pool in the atria and form clots (because the blood is not fully pumped out after each heartbeat), which is why patients with atrial fibrillation as more prone to strokes and heart attacks. About a third of strokes in patients 80 years or older are attributable to atrial fibrillation. Specific risks that increase chances of Atrial Fibrillation are Stress, smoking and heavy drinking, obesity all make it harder to treat. Susceptibility may also be inherited
Simple EKG tests can be performed to determine if the patient is in Atrial Fibrillation. The "P" wave normally a well defined small wave, once per heart beat turns into a series of smaller erratic waves. Treatment usually includes catheter ablation, where the sources of irregularity are located and destroyed in the heart.
References
Atrial Fibrillation at the American Heart Association [1]