Out-of-hospital cardiac arrests in Victoria, 2003-2022: retrospective analysis of Victorian Ambulance Cardiac Arrest Registry data.

Objectives: To examine changes in out-of-hospital cardiac arrest (OHCA) characteristics and outcomes during 2003-2022, and 12-month outcomes for people who experienced OHCA during 1 January 2010 - 30 June 2022.

Study design: Retrospective observational study; analysis of Victorian Ambulance Cardiac Arrest Registry (VACAR) data.

Setting, participants: OHCA events in Victoria not witnessed by emergency medical services personnel, 1 January 2003 - 31 December 2022.

Main outcome measures: Crude and age-standardised annual OHCA incidence rates; survival to hospital discharge.

Results: Of 102 592 OHCA events included in our analysis, 67 756 were in men (66.3%). The age-standardised incidence did not change significantly across the study period (2003: 89.1 cases, 2022: 91.2 cases per 100 000 population; for trend: P = 0.50). The proportion of OHCA cases with attempted resuscitation by emergency medical services in which bystanders attempted cardio-pulmonary resuscitation increased from 40.3% in 2003/2004 to 72.2% in 2021/2022, and that of public access defibrillation from 0.9% to 16.1%. In the Utstein comparator group (witnessed OHCA events in which the initial cardiac rhythm was ventricular fibrillation or ventricular tachycardia, with attempted resuscitation by emergency medical services), the odds of survival to hospital discharge increased during 2003-2022 (adjusted odds ratio (aOR), 3.08; 95% confidence interval [CI], 2.22-4.27); however, the odds of survival was greater than in 2012 only in 2018 (aOR, 1.37; 95% CI, 1.04-1.80) and 2019 (aOR, 1.68; 95% CI, 1.28-2.21). The COVID-19 pandemic was associated with reduced odds of survival (aOR, 0.63; 95% CI, 0.54-0.74). Of 3161 people who survived OHCA and participated in 12-month follow-up, 1218 (38.5%) reported full health according to the EQ-5D.

Conclusion: Utstein survival to hospital discharge increased threefold during 2003-2022, and the proportions of cases in which bystanders provided cardio-pulmonary resuscitation or public access defibrillation increased. The COVID-19 pandemic was associated with a substantial reduction in survival, and new strategies are needed to improve outcomes.