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

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. 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. 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 p<0.050). Most rearrest rhythms were non shockable (76%). More epinephrine doses given by EMS were associated with a higher likelihood of rearrest in the ED (OR: 1.60, 95%CI=1.26, 1.95). Shockable primary arrest rhythm and Hispanic ethnicity were predictors of survival while rearrest, coronary artery disease and longer time to ROSC were associated with increased mortality. 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.