Abstract Body: Background: Determining factors predicting return of spontaneous circulation (ROSC) and survival after out of hospital cardiac arrest (OHCA) are a high priority for guiding clinical decision making and understanding differences in patient outcomes. Although sex differences in OHCA outcomes have been described, there are inconsistent reports, and mechanisms underlying these differences remain unclear.

Aim: To determine whether sex differences and arrest factors are associated with ROSC and survival after OHCA.

Hypothesis: Sex differences in both ROSC and survival are associated with differences in both arrest characteristics and care delivery.

Methods: Single site observational study of consecutive adult emergency medical services (EMS) patients with OHCA at a large tertiary care center between 1/1/2018-3/31/2024. EMS reports, continuous EMS ECG recordings and electronic health records were analyzed to identify the presence ROSC and determine demographics, arrest characteristics, and survival. Statistical significance was determined using Chi-square and logistic regression (LR) analyses.

Results: 344 (71%) patients had ROSC and 139 patients (29%) had no ROSC. Patients with ROSC vs. no ROSC were similar regarding age, race, and ethnicity. Patients with ROSC were more likely to be female (p<0.003), and female patients with ROSC were more likely to have both a primary arrest rhythm of VT/VF and asystole (p <0.05), rearrest (p<0.013), and had a longer time from arrest to ROSC (34 vs. 25 min, p<0.1). Interestingly, in a LR model, female sex was associated with greater 6-month survival (OR: 3.3, 1.6-6.5, p<0.003). There were no sex differences in patients receiving post-arrest cardiac catheterization or targeted temperature management.

Conclusion: Despite generally worse arrest characteristics, female sex was associated with increased ROSC and survival. Given this, and similar delivery of post-arrest care, these data suggest that in this cohort, sex differences, rather than care delivery, may underlie differences in outcome. Whether additional disparities in arrest and post-arrest care contribute will be important to determine.