The novel coronavirus disease 2019 (COVID-19) was first found in China in December 2019 and spread rapidly across the world, leading to the COVID-19 pandemic [1,2]. After the first case of COVID-19 emerged in Japan, an explosive growth of COVID-19 cases overwhelmed the health care system. Since most hospitals and the emergency medical system (EMS) in Japan were not originally designed or specialized for the treatment of contagious viruses [3], the unprecedented crisis made it difficult for healthcare systems to maintain EMS. During the COVID-19 pandemic, patients with time-dependent diseases such as out-of-hospital cardiac arrest (OHCA), one of the most difficult challenges and a major public concern [4,5], were strongly affected. Outcomes for OHCA patients were strongly influenced by COVID-19, since the spread of this contagious disease mandated social distancing, resulting in bystanders avoiding helping people with cardiac arrest (CA) and less automated external defibrillator use, leading to a decrease of appropriate prehospital treatment and worse outcomes [6,7,8,9].

Japan is one of the countries where extracorporeal resuscitation (ECPR) is commonly used to advance resuscitation strategies. ECPR has been implemented in some tertiary care hospitals; subsequently, favorable outcomes have been reported throughout Japan [10,11,12]. The International Liaison Committee on Resuscitation suggests that ECPR, in settings where it can be implemented, may be considered a rescue therapy for selected patients with CA when conventional cardiopulmonary resuscitation (CPR) fails [13]. Although the efficacy and cost-effectiveness of ECPR remain uncertain, its use has continued even during the COVID-19 pandemic.

Notably, several studies have indicated an association between OHCA patient outcomes and the COVID-19 pandemic all over the world [14,15,16]. However, no studies have yet investigated the association between ECPR and the COVID-19 pandemic. In the future, it is possible that new/novel virus will emerge and an unprecedented pandemic will occur again. As clinicians, we must cope with new crises according to evidence, experiences, and lessons learned from the COVID-19 pandemic.

Thus, in this study, we aimed to examine whether there were differences in outcomes for OHCA patients who received ECPR during the COVID-19 pandemic, and to compare survival at discharge and favorable neurological outcomes between OHCA patients who received ECPR before and during the pandemic.