Chain of Survival
The AHA Chains of Survival describe the sequence of actions that give a cardiac-arrest victim the best chance of survival. There are separate chains for out-of-hospital and in-hospital arrest because the resources and first responders differ.
Out-of-hospital versus in-hospital chains
The out-of-hospital Chain of Survival begins with recognition of the arrest and activation of the emergency response system (calling 911 and getting an AED), followed by immediate high-quality CPR, rapid defibrillation, advanced resuscitation by EMS, post-cardiac-arrest care, and recovery. The in-hospital chain begins instead with surveillance and prevention — recognizing deterioration early and preventing the arrest — then activation of the rapid response or code team, high-quality CPR, defibrillation, and post-arrest care. A layperson or lone provider outside the hospital relies on the community and EMS, whereas hospital patients are surrounded by monitoring and a professional team.
Why each link matters
The chain is only as strong as its weakest link: delayed recognition, delayed CPR, or delayed defibrillation each sharply lowers survival. Early bystander CPR can double or triple survival, and for a shockable rhythm every minute without defibrillation reduces survival by roughly 7 to 10 percent. This is why the BLS provider's priorities are to recognize arrest quickly, start compressions immediately, and get an AED on the chest as fast as possible.