ECPR eligible refractory out of hospital cardiac arrests – A post-hoc analysis of the EVIDENCE randomised controlled trial and Registry

BACKGROUND The use of Extracorporeal cardiopulmonary resuscitation (ECPR) for refractory out-of-hospital cardiac arrest (OHCA) is increasing. The EVIDENCE study of refractory OHCA transportation did not report a survival benefit of expedited transportation to hospital, likely in part owing to a very limited number of patients receiving ECPR. The reasons for this, the total potential numbers of ECPR patients and the effects of different system changes would assist in trial and clinical service planning. METHODS A pre-specified, post-hoc analysis was performed of the randomised controlled trial (RCT) - EVIDENCE (ACTRN12621000668808) and the contemporaneous EVIDENCE Registry (non-randomised data), which examined assessing ECPR eligibility, why ECPR was not provided and survival to hospital discharge. A truly eligible hospital-based ECPR patient was defined as a patient meeting ECPR criteria and arriving to an ECPR-capable hospital within 1 hour of arrest with no sustained ROSC within ECPR service hours (office hours). Potential ECPR patients (meeting ECPR criteria with no ROSC on-scene) were also defined and quantified. RESULTS Thirty-eight of 1497 (3%) OHCA patients in the combined RCT and Registry were truly eligible for hospital-based ECPR. Main reasons for exclusion of potential ECPR patients were arrival to hospital >1-hour post-arrest, arrival to a non-ECPR-capable centre, and/or arrival outside of ECPR-capable hours. Seventy-nine (5%) and 350 (23%) patients were identified as potential hospital-based and pre-hospital ECPR candidates, respectively. Survival to hospital discharge of potential ECPR patients was 5%. CONCLUSION Only a small percentage of OHCA patients were considered eligible for ECPR, predominantly due to challenges in accessing ECPR therapy. ECPR-eligible patients, not treated with ECPR, have very poor survival outcomes.