Résumé : Return of spontaneous circulation occurs in less than 10% of patients with cardiac arrest undergoing cardiopulmonary resuscitation (CPR) for more than 15 minutes. Studies suggest that extracorporeal life support during cardiopulmonary resuscitation (ECPR) improves survival rate in these patients. These studies, however, are hampered by their non-randomized, observational design and are mostly single-center. A multicenter, randomized controlled trial is urgently warranted to evaluate the effectiveness of ECPR. Hypothesis: We hypothesize that early initiation of ECPR in refractory out-of-hospital cardiac arrest (OHCA) improves the survival rate with favorable neurological status. Study design: The INCEPTION trial is an investigator-initiated, prospective, multicenter trial that will randomly allocate 110 patients to either continued CPR or ECPR in a 1:1 ratio. Patients eligible for inclusion are adults (≤ 70 years) with witnessed OHCA presenting with an initial rhythm of ventricular fibrillation (VF) or ventricular tachycardia (VT), who received bystander basic life support and who fail to achieve sustained return of spontaneous circulation within 15 minutes of cardiopulmonary resuscitation by emergency medical services. The primary endpoint of the study is 30-day survival rate with favorable neurological status, defined as 1 or 2 on the Cerebral Performance Category score. The secondary endpoints include 3, 6 and 12-month survival rate with favorable neurological status and the cost-effectiveness of ECPR compared to CCPR. The INCEPTION trial aims to determine the clinical benefit for the use of ECPR in patients with refractory OHCA presenting with VF/VT. Additionally, the feasibility and cost-effectiveness of ECPR will be evaluated.