OHCA is the leading cause of mortality, globally. The incidence of shockable cardiac arrest is declining, with over half the patients with OHCA now being in asystole.
“In this study, we systematically reviewed the literature on patients with asystolic OHCA to determine global pooled outcomes, incidence rates and factors associated with survival.”
The Study
Dwivedi DB et al. Incidence and outcomes of out-of-hospital cardiac arrest from initial asystole: a systematic review and meta-analysis. Resuscitation 212 (2025) 110629.
What They Did
In this systematic review and meta-analysis, interventional and observational studies were included if an EMS attended or treated OHCA population, if the initial cardiac rhythm was asystole and there was sufficient data to calculate the primary outcome of survival to hospital discharge or 30 days.
Primary outcome
The pooled rate of survival to hospital discharge or 30 days.
Secondary outcomes
The pooled proportion of event survivors, patients achieving ROSC, survivors with good neurological outcome at longest-follow-up.
What They Found
82 studies were included, with a total 540,054 EMS-treated patients with OHCA of all aetiologies, in 35 countries. The majority of studies were retrospective cohort studies (75.6%) and registry-based data collection was reported in thirty (36.5%) studies.
The pooled rate of initial asystole was 53.0% (95% CI: 49.0%, 58.0%). Survival to hospital discharge or 30 days ranged between 0% and 23.0% with the crude survival rate being 1.9% (9931 survivors from 531,049 EMS treated patients with known outcome). The results show a consistently poor survival from asystole in OHCA.
Survival to hospital discharge or 30 days was 1.5%(n = 9931), with 0.6% achieving favourable neurological outcomes. No variables including witnessed arrest, bystander CPR, arrest location, endotracheal intubation, IV/I/O adrenaline administration, EMS response time and transport time, were significantly associated with event survival.
The review is limited by the heterogeneity of the results in the studies, plus the fact that some studies that were retrospective, some used registry data, and some data was missing all together, whilst some variables such as duration of CPR, that may have impacted survival, were not available to review.
What is clear and known to us, is that the rate of defibrillatable OHCA is decreasing and the rate of asystole is high with poor outcomes. This leads the authors of this study to talk about ‘prevention’ rather than management.
