fibrillation

Fibrillation is the rapid, irregular, and unsynchronized contraction of muscle fibers. An important occurrence is with regard to the heart.

==Cardiology== There are two major classes of cardiac fibrillation: atrial fibrillation and ventricular fibrillation. Atrial fibrillation is an irregular and uncoordinated contraction of the cardiac muscle of atria. It can be a chronic condition, usually treated with anticoagulation and sometimes with conversion to normal sinus rhythm. In this condition the normal electrical pulses coming from the sinoatrial node are overwhelmed by disorganized electrical impulses usually originating in the roots of the pulmonary veins, leading to irregular conduction of impulses to the ventricles which generate the heartbeat. Ventricular fibrillation is an irregular and uncoordinated contraction of the cardiac muscle of ventricles. It is a common cause of cardiac arrest and is usually fatal if not reversed by defibrillation.