An abnormal and irregular heart rhythm in which there are rapid uncoordinated fluttering contractions of the lower chambers (ventricles) of the heart. It is a life-threatening heart rhythm that results in a rapid, inadequate heartbeat. It is because the heart doesn't pump appropriate amount of blood during ventricular fibrillation, sustained VF can cause low blood pressure, loss of consciousness and lead to death also. Emergency treatment constitutes an immediate defibrillation along with an automated external defibrillator (AED) and cardiopulmonary resuscitation (CPR). . People develop irreversible brain damage after about 5 minutes because oxygen no longer reaches the brain. Death soon follows. Atrial fibrillation causes an irregular heart rate. If you check your pulse, you will often feel a "fluttering." When atrial fibrillation is new in onset or poorly controlled by medications you will often feel your heart pumping fastly. . It could be diagnosed by ECG, Blood tests. Chest X-ray., Echocardiogram. Coronary catheterization (angiogram), computerized tomography (CT), Magnetic resonance imaging (MRI). Cardiopulmonary resuscitation (CPR) must be started within a few minutes as an emergency response and hence life of the person could be saved.