Out-of-hospital cardiac arrest (OHCA) describes a cardiac arrest that occurs outside a hospital setting, such as at home, at work, in a public place, or on the street. It is distinguished from in-hospital cardiac arrest (IHCA), where medical staff and resuscitation equipment are immediately available.
OHCA accounts for the vast majority of cardiac arrests in the UK. Around 30,000 OHCA attempts are made by ambulance services in the UK each year. Survival to hospital discharge is around 8 to 10% overall, though this varies considerably depending on initial rhythm, witness status, and speed of response. OHCA in a public location with immediate bystander CPR and early defibrillation carries significantly better survival odds than an unwitnessed arrest at home.
**The key determinants of survival are:**
– Early recognition and calling 999
– Immediate bystander CPR (doubles or triples survival rates)
– Early defibrillation with an AED (each minute without defibrillation reduces survival by approximately 10%)
– Rapid ambulance arrival and advanced paramedic care
– High-quality post-resuscitation care in hospital, including targeted temperature management and specialist investigation
These steps are described collectively as the Chain of Survival. The growing network of publicly accessible AEDs and [dispatcher-assisted CPR](/glossary/dispatcher-assisted-cpr/) guidance from emergency call handlers have improved OHCA outcomes in recent years.
Sudden Cardiac Arrest UK exists specifically to support survivors of OHCA and their families, and to campaign for wider access to defibrillators and CPR training.