Epidemiology, outcomes, and associated factors of out-of-hospital cardiac arrest in Zhejiang, China: a province-wide registry study

Out-of-hospital cardiac arrest (OHCA) remains a major public health challenge with poor survival worldwide. Although previous studies have described OHCA epidemiology and outcomes in China, province-wide data comprehensively characterizing patient and arrest characteristics, clinical outcomes, and factors associated with survival and neurological recovery remain limited. To characterize the epidemiology and outcomes of OHCA and identify factors associated with 30-day survival and favorable neurological outcome in Zhejiang, China. We conducted a retrospective analysis of prospectively collected data from the Zhejiang Emergency Registry (ZER), a mandatory province-wide emergency medical services (EMS) registry based on Utstein-style standardized reporting in Zhejiang, China. Adult EMS-treated OHCA cases of medical etiology between January 2024 and December 2025 were included. Patient characteristics, arrest circumstances, community response, dispatcher-related factors, EMS characteristics, prehospital interventions, and clinical outcomes were described. Multivariable logistic regression was used to identify factors associated with 30-day survival and favorable neurological outcome. Among 17,646 EMS-treated OHCA patients, 531 (3.0%) survived to 30 days and 345 (2.0%) achieved favorable neurological outcome. Bystander CPR was performed in 47.7% of cases, while dispatcher recognition of OHCA, dispatcher-assisted CPR, and bystander automated external defibrillator (AED) use occurred in 25.1%, 20.0%, and 1.8% of cases, respectively. Home arrests accounted for 64.3% of cases and had a 30-day survival rate of 2.2%. Both 30-day survival and favorable neurological outcome progressively declined with increasing EMS response time. In multivariable analysis, shockable rhythm showed the strongest association with both 30-day survival and favorable neurological outcome. Younger age, witnessed arrest, bystander CPR, bystander AED use, dispatcher recognition, dispatcher-assisted CPR, and shorter EMS response time were independently associated with improved 30-day survival. In this province-wide registry study, 30-day survival and favorable neurological outcomes after OHCA remained low in Zhejiang, China. Low rates of dispatcher recognition, dispatcher-assisted CPR, and bystander AED use were observed, and outcomes declined progressively with increasing EMS response time. Several factors were independently associated with 30-day survival and favorable neurological outcome. These findings provide population-level evidence to inform future quality-improvement strategies for OHCA care.