Ventricular fibrillation (V-fib or VF) is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Because there is no co-ordinated contraction of the ventricles, there is no significant cardiac output, thus fulfilling the conditions of a cardiac arrest. It is the most commonly identified arrhythmia in cardiac arrest patients, and requires prompt treatment if identified on electrocardiography. Left untreated, ventricular fibrillation will quickly degenerate into asystole and is associated with a high mortality. Patients who are not revived soon enough (within about five minutes at room temperature) can sustain irreversible brain damage and can become brain-dead, because of cerebral hypoxia.