Fibrillation is a term for the uncoordinated contractions of the heart muscle by de-synchronization between the different chambers of the heart. It is called atrial fibrillation when it affects the atria, and ventricular fibrillation when it affects the ventricles. Cardiac atrial fibrillation, known by the acronym AF, is an abnormal heart rhythm characterized by sporadic contractions of the ventricles of the heart. It may be permanent, but it can also occur occasionally, be felt by the person as palpitations, and disappear suddenly. It is identified by recording the heart and the purpose of the treatment is twofold: to fight against the major complication of AF, an embolism, by thinning the blood, and to reduce the speed of the beating heart by drugs or sometimes electric shock. Ventricular fibrillation is much more serious and can quickly lead to cardiac arrest.