The Full form of AED is Automated External Defibrillator. AED is a portable electronic device that automatically diagnoses the life-threatening cardiac arrhythmias of ventricular fibrillation and pulseless ventricular tachycardia, and is able to treat them through defibrillation, the application of electricity which stops the arrhythmia, allowing the heart to re-establish an effective rhythm. Although advances in emergency cardiac (heart) care continue to improve the chances of surviving cardiac arrest, but still it remains a leading cause of death in many parts of the world. Each year, almost 350,000 people die from heart disease in US. Half of these will die suddenly, outside of the hospital, because their heart stops beating. Most of these deaths occur with no or little warning, from a syndrome called sudden cardiac arrest. Ventricular fibrillation is a disturbance in the heart rhythm and is the most common cause of sudden cardiac arrest. Ventricular fibrillation is dangerous because it cuts off blood supply to the brain and other vital organs. The ventricles pump blood out of the heart and into the blood vessels. This blood supplies oxygen and other nutrients to cells, organs, and other structures. If these structures do not receive enough blood, they start to shut down, or fail.