Patient and arrest characteristics associated with rearrest and mortality following out of hospital cardiac arrest.

Background: Rearrest following return of spontaneous circulation (ROSC) after out-of-hospital cardiac arrest (OHCA) is a frequent complication and a strong predictor of mortality. Despite its prevalence, the patient-level risk factors and pathophysiology underlying rearrest, particularly in the early post-ROSC period, defined as during emergency medical services (EMS) and emergency department (ED) care, are poorly understood. We aimed to characterize the incidence of rearrest during the early post-ROSC phase, identify patient-specific risk factors, and assess its impact on long-term outcomes. Methods: We performed a retrospective, single-center observational study of 344 consecutive adult OHCA patients with ROSC (January 1, 2018-March 14, 2024). Rearrest was identified using EMS reports, ECG recordings, and electronic health records. Patient and arrest characteristics were collected. The primary outcomes were rearrest and six-month survival. Results: Rearrest occurred in 172 of 344 patients (50%), with 89% occurring in the early post-ROSC period. Rearrest was associated with older age, female sex, hypertension and longer time to ROSC (all Conclusions: Rearrest early after ROSC is common and independently predicts mortality. Our findings support early identification of high-risk patients to guide targeted post-ROSC monitoring and intervention strategies to prevent rearrest.