Aetiology of resuscitated out-of-hospital cardiac arrest treated at hospital

Introduction: Precipitating aetiology of out-of-hospital cardiac arrest (OHCA), as confirmed by diagnostic testing or autopsy, provides important insights into burden of OHCA and has potential implications for improving OHCA survivorship. This study aimed to describe the aetiology of non-traumatic resuscitated OHCAs treated at hospital within a local health network according to available documentation, and to investigate differences in outcome between aetiologies. Methods: Observational retrospective cohort study of consecutive OHCA treated at hospital within a local health network between 2011–2016. Cases without sustained ROSC (≥20 minutes), unverified cardiac arrest, and retrievals to external acute care facilities were excluded. A single aetiology was determined from the hospital medical record and available autopsy results. Survival to hospital discharge was compared between adjudicated aetiologies. Results: In the 314 included cases, distribution of precipitating aetiology was 53% cardiac, 18% respiratory, 3% neurological, 6% toxicological, 9% other, and 11% unknown. A presumed cardiac pre-hospital diagnosis was assigned in 235 (84%) cases, 20% of which were incorrect after exclusion of unknown cases. Rates of survival to hospital discharge varied significantly across aetiologies: cardiac 64%, respiratory 21%, neurological 0%, toxicological 58%, other 32% (p < 0.001). A two-fold difference in survival was observed between cardiac and non-cardiac aetiologies (64% versus 29%, excluding unknown, p < 0.001). Conclusions: Non-cardiac aetiologies represented a substantial burden of resuscitated OHCA treated at hospital within a local health network and were associated with poor outcome. The results confirmed that true aetiology was not evident on initial examination in 1 in 5 cases with a pre-hospital cardiac diagnosis.