The chain of survival refers to a series of actions that, when put into motion, reduce the mortality associated with cardiac arrest. Like any chain, the chain of survival is only as strong as its weakest link. The four interdependent links in the chain of survival are early access, early CPR, early defibrillation, and early advanced cardiac life support
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Background
The "chain of survival" metaphor was developed by Mary M. Newman, MS, of the Sudden Cardiac Arrest Foundation, and used as a slogan for the 1988 Conference on Citizen CPR, and described in an article she wrote for the Journal of Emergency Medical Services in 1989, and in an editorial she wrote for the first issue of Currents in Emergency Cardiac Care in 1990. The American Heart Association adopted the concept and elaborated on it in its 1992 guidelines for cardiopulmonary resuscitation and emergency cardiac care, The International Liaison Committee on Resuscitation (ILCOR) echoed the concept in 1997.
Early access
Ideally, someone must recognize an impending cardiac arrest or otherwise witness the cardiac arrest and activate the EMS system as early as possible with an immediate call to the emergency services. Unfortunately, many persons experiencing symptoms (for example, angina) that may lead to a cardiac arrest ignore these warning symptoms or, recognizing these warning symptoms correctly, fail to activate the EMS system, preferring to contact relatives instead (the elderly often contact their adult offspring rather than contact emergency services).
Early CPR
In order to be most effective, bystander CPR should be provided immediately after collapse of the patient. Properly performed CPR can keep the heart in a shockable ventricular fibrillation for 10–12 minutes longer.
Early defibrillation
Most adults who can be saved from cardiac arrest are in ventricular fibrillation or pulseless ventricular tachycardia. Early defibrillation is the link in the chain most likely to improve survival. Public access defibillation may be the key to improving survival rates in out-of-hospital cardiac arrest, but is of the greatest value when the other links in the chain do not fail.
Early advanced care
Early advanced cardiac life support by paramedics is another critical link in the chain of survival. In communities with survival rates > 20%, a minimum of two of the rescuers are trained to the advanced level. In some countries, EMS delivery may be performed by ambulance officers, paramedics, nurses, or doctors.