To improve the prehospital care of victims of cardiac arrest, the American Heart Association has developed the Chain of Survival, wherein a sequence of interventions results in improved survival after a cardiac arrest. These steps include early access to the emergency medical services by calling 911, early cardiopulmonary resuscitation (CPR) when needed, early defibrillation when indicated, and early advanced medical care. Research shows that early defibrillation is the most important single intervention. Immediate defibrillation can result in survival rates of more than 90%. Each minute of cardiac arrest, however, leads to a 10% reduction in survival, so early treatment is very important. The AED can be used by trained medical and laypersons in locations such as shopping malls, golf courses, businesses, airports, airplanes, casinos, convention centers, hotels, sports arenas, and other public locations. Use of the AED by untrained bystanders also can lead to improved survival for victims of cardiac arrest.