Sex differences in extracorporeal cardiopulmonary resuscitation for out-of-hospital cardiac arrest: nationwide multicenter retrospective study in Japan.

Background: Previous studies examining sex differences in patients undergoing extracorporeal cardiopulmonary resuscitation (ECPR) for out-of-hospital cardiac arrest (OHCA) have indicated that women have favorable outcomes; however, detailed evidence remains lacking. We aimed to investigate sex differences in the backgrounds and outcomes of patients undergoing ECPR for OHCA.

Methods: This study was a secondary analysis of the registry from the SAVE-J II study, a retrospective multicenter study conducted in Japan from 2013 to 2018. Adult patients without external causes who underwent ECPR for OHCA were included. The primary outcome was a favorable neurological outcome (Cerebral Performance Status 1 or 2) at hospital discharge. We used multilevel logistic regression to evaluate the association of sex differences, adjusting for center-level (hospital) and individual-level variables (patient background, cardiac arrest situation, and in-hospital intervention factors). For sensitivity analyses, we performed three models of multilevel logistic regression when selecting confounders.

Results: Among the 1819 patients, 1523 (83.7%) were men, and 296 (16.3%) were women. The median age (61.0 vs. 58.0 years), presence of a witness (78.8% vs. 79.2%), and occurrence of bystander CPR (57.5% vs. 61.6%) were similar between groups. Women were more likely to present with an initial non-shockable rhythm (31.7% vs. 49.7%), as well as a non-shockable rhythm at hospital arrival (52.1% vs. 61.5%) and at ECMO initiation (48.1% vs. 57.1%). The proportion of favorable neurological outcomes was 12.3% in males and 15.9% in females (p = 0.10). Multilevel logistic regression analysis showed that the female sex was significantly associated with a favorable neurologic outcome at discharge (adjusted odds ratio: 1.60 [95% confidence interval: 1.05-2.43]; p = 0.03). This advantage in women was consistently observed in the sensitivity analyses.

Conclusions: The female sex is significantly associated with favorable neurological outcomes at hospital discharge in patients who received ECPR for OHCA.