Changes in the incidence of out-of-hospital cardiac arrest: Differences between cardiac and non-cardiac aetiologies.

Abstract Aim We aimed to assess temporal changes in the incidence of OHCAs of presumed cardiac and non-cardiac aetiologies. Methods We conducted a retrospective cohort study of OHCAs in Victoria, Australia between 2000-2017. Annual adjusted incidence rates in presumed cardiac and non-cardiac OHCA were calculated with 95% confidence intervals (95% CI), assuming a Poisson distribution. Annual percent changes in the adjusted rates were calculated from Poisson regression models. Results During an 18-year period, 90,688 emergency medical service (EMS)-attended OHCAs were included. Of those, 64,422 (71.0%) were of presumed cardiac and 26,266 (29.0%) were of non-cardiac aetiology. Over the 18-year period, there was a 12.6% (95% CI: 10.8%, 14.4%) relative decline in presumed cardiac events and this was driven largely by a reduction in cases with an initial shockable rhythm (23.4%; 95% CI: 19.8%, 27.0%) and cases in patients aged 65-79 years (48.6%; 95% CI: 45.0%, 50.4%). Conversely, there was a 28.8% (95% CI: 27.0%, 32.4%) relative increase in non-cardiac events over the 18-year period, and this was driven by an increase in initial pulseless electrical activity events (93.6%; 95% CI: 86.4%, 100.8%) and cases in patients aged ≥80 years (93.6%; 95% CI: 86.4%, 100.8%). Precipitating events with the largest 18-year increase in incidence were non-traumatic exsanguination (115.2%; 95% CI: 95.4%, 133.2%), respiratory (66.6%; 95% CI: 59.4%, 73.8%), and neurological (63.0%; 95% CI: 50.4%, 77.4%). Conclusion Our data indicates that by 2052, non-cardiac aetiologies could be the leading cause of OHCA in our region. These findings have important EMS-system and public health implications.