Impact of system efficiency on out-of-hospital cardiac arrest outcomes and hospital stay: an observational study from Lombardia CARe

BACKGROUND: Out-of-hospital cardiac arrest (OHCA) remains a major public health concern, characterised by high mortality and substantial variability in survival rates. As patient and event characteristics are largely unmodifiable, system efficiency is essential to improve survival. METHODS: We conducted a retrospective cohort study using data from the Lombardia Cardiac Arrest Registry, including 12,532 OHCA cases (2015-2023). Multivariate logistic regression models were applied to assess the relationship between emergency medical service (EMS) arrival time and prehospital mortality, as well as long-term outcomes according to system efficiency. Furthermore, a sub-cohort of 515 hospitalised patients was analysed to evaluate hospital stay and healthcare costs. RESULTS: Prehospital event mortality increased from 74.7% to 93.2% with longer EMS response time, with survival decreasing by 0.6% for each additional minute of EMS delay (OR 1.03; 95% CI 1.02-1.05). Higher system efficiency, characterised by bystander cardiopulmonary resuscitation and EMS arrival within 10 minutes, was associated with markedly higher survival at hospital admission (25.4% vs. 7.6%) and at 12 months (13.0% vs. 1.6%), as well as improved neurological outcomes and discharge survival among hospitalised patients. Higher hospital costs were observed among patients in the high-efficiency system group, while less efficient systems showed higher costs per survivor at 12 months follow-up (€61,781 vs. €48,985). CONCLUSIONS: System responsiveness is a key modifiable factor influencing outcomes after OHCA, with each minute of EMS delay substantially reducing survival odds. Enhancing the entire chain of survival is essential to improve patient outcomes and reduce the indirect societal costs associated with OHCA.