Background: The aim of the European Registry of Cardiac Arrest (EuReCa) network is to provide high quality evidence on epidemiology of out-of-hospital cardiac arrest (OHCA) in Europe by supporting and developing cardiac arrest registries and performing European-wide studies. To date, the EuReCa ONE and EuReCa TWO studies have involved around 28 countries, with population covered increasing from the first to the second study. The aim of the EuReCa THREE study is to build on previous work and to support the promotion of quality data collection on OHCA throughout Europe.

Methods/design: EuReCa THREE will be the third prospective cohort study on epidemiology of OHCA and will involve around 30 European countries. The study will be conducted between 1st September and 30th November 2022. Data will be collected on cardiac arrest cases attended, resuscitation attempted, patient and cardiac arrest event characteristics and outcomes (including return of spontaneous circulation, status on hospital arrival and discharge). A particular focus for EuReCa THREE will be to describe key time intervals in OHCA management; time from call to EMS arrival on scene, time from cardiac arrest to start CPR, time from EMS arrival to delivery of patient to hospital.EuReCa THREE was registered with the German Registry of Clinical Trials Registration Number: DRKS00028591 searchable via WHO meta-registry (https://apps.who.int/trialsearch/).

Discussion: The EuReCa THREE study will increase our knowledge on longitudinal OHCA epidemiology and provide new knowledge on crucial time intervals in OHCA management in Europe. However, the primary aim of building a network to support quality data on OHCA, remains the central tenant of the EuReCa project.