Survival after an out-of-hospital cardiac arrest (OHCA) relies heavily on rapid CPR and prompt defibrillation. Although many automated external defibrillators (AEDs) exist across communities, they are used in only a small fraction of emergencies. One major barrier is the lack of a unified national system mapping their locations for UK ambulance services, potentially limiting their timely use. To address this gap, stakeholders in resuscitation collaborated with ambulance organisations to create a single national platform that records AED placement across the UK. The British Heart Foundation, working jointly with the Association of Ambulance Chief Executives, all UK ambulance services, the Resuscitation Council UK, and St John Ambulance, designed The Circuit, a nationwide AED registry. The platform allows AED owners to upload details about device placement, accessibility, and hours of availability. These data are automatically linked to ambulance computer-aided dispatch systems, giving emergency call handlers real-time access to the nearest usable AED. All 14 ambulance services across the UK have now adopted The Circuit. Since 2019, the system has accumulated records for 82,108 AEDs. Importantly, over half (54%) of these devices had not been previously recorded by any ambulance service, representing newly captured information. The Circuit offers a single nationally coordinated source of AED location data for UK ambulance services. Since implementation, the number of known AEDs has doubled. Future integration of this registry with patient outcome datasets will help determine whether increased visibility and accessibility of AEDs translates into improved survival after OHCA.
