Abstract 12069: Long-Term Trends in the Incidence and Outcome of Refractory and Non-Refractory Ventricular Fibrillation Cardiac Arrest

Abstract

Introduction: Although many developed countries are reporting temporal improvements in out-of-hospital cardiac arrest (OHCA) outcomes from initial shockable rhythms, trends in the incidence and outcome of refractory ventricular fibrillation are not well understood. Methods: Between 2010 and 2019, we performed a retrospective observational study of OHCA from a population-based registry in Victoria, Australia. We included all adult, non-traumatic OHCA with an initial shockable rhythm. Temporal trends in incidence and survival to hospital discharge were compared across non-refractory and refractory OHCA, defined as cases receiving 3 or more consecutive shocks for a persistent shockable rhythm. Risk-adjusted logistic regression models were used to describe the year-on-year change in the likelihood of refractory OHCA and survival to hospital discharge. Results: Of the 7,267 initial shockable OHCA with an attempted resuscitation, 4168 (57.4%) and 3,099 (42.6%) were non-refractory and refractory OHCA, respectively. The proportion of cases with refractory OHCA declined over the study period from 48.4% in 2010 to 40.2% in 2019 (p trend <0.001). Unadjusted survival to hospital discharge was higher in non-refractory OHCA (46.3% vs. 25.8%, p<0.001), although both populations experienced increases in survival over time (p trend <0.05 for both). After adjustment for arrest confounders, the likelihood of refractory VF decreased by 4.4% every year (adjusted odds ratio [AOR]: 0.96, 95% CI: 0.94, 0.97; p<0.001). Factors reducing the likelihood of refractory OHCA were female sex, bystander CPR, arrest witnessed by emergency medical services, and public location. In the survival model, refractory OHCA was independently associated with a reduction in survival to hospital discharge (AOR 0.50, 95% CI: 0.45, 0.56; p<0.001). Temporal improvements in survival were observed year-on-year (AOR 1.03, 95% CI: 1.02, 1.05; p<0.001) and this did not differ between non-refractory and refractory OHCA (group interaction, p = 0.51). Conclusions: The incidence of refractory OHCA is declining in our region and survival outcomes are improving. Further research identifying factors contributing to the decline in refractory OHCA may help to improve outcomes further.