Factors influencing the prognosis of out-of-hospital cardiac arrest during the coronavirus disease 2019 pandemic: an analysis of the Utstein Registry in Aichi, Japan

Out-of-hospital cardiac arrest (OHCA) remains a major global public health concern, with survival rates remaining low despite decades of efforts to enhance emergency response systems. The coronavirus disease 2019 (COVID-19) pandemic significantly impacted emergency medical services (EMS), causing longer response intervals, changes in airway management practices, and reduced bystander intervention, which may have altered the prognostic factors associated with OHCA outcomes. This study aimed to identify factors associated with favorable neurological outcomes among patients with OHCA and investigate how these factors changed across three periods: pre-COVID-19 (2017–2019), early COVID-19 (2020–2021), and late COVID-19 (2022–2023). We conducted a retrospective observational study using Utstein-style Registry data from Aichi Prefecture, Japan (2017–2023). Patient demographics, bystander interventions, EMS activities, and outcomes were compared across periods. Neurological outcomes were assessed using the Cerebral Performance Category, with scores of 1–2 considered favorable (mortality recorded as Cerebral Performance Category 5). To identify factors independently associated with favorable outcomes, logistic regression analyses were separately performed for each period. Of 51,890 patients, the proportion of favorable neurological outcomes declined from 4.6% (pre-COVID-19) to 3.4% (early) and 3.1% (late). In the regression model excluding return of spontaneous circulation, the adjusted odds ratio (aOR) for initial ventricular fibrillation/pulseless ventricular tachycardia decreased from 4.340 (pre) to 3.516 (early), whereas the aOR for witnessed arrest increased from 5.866 (pre) to 8.097 (early). During the early period, the association of bystander defibrillation peaked, whereas the negative association of advanced airway management progressively strengthened, with aORs decreasing from 0.268 (pre) to 0.182 (late). Prognostic factors for favorable neurological outcomes changed across the three COVID-19 periods, indicating that the pandemic altered both the OHCA case mix and the relative importance of key resuscitation elements. Continuous adaptation of EMS systems is crucial for sustaining outcomes under shifting clinical and operational conditions.