AED applied, not recommending defibrillation - A validation study of the new variable “AED” in the Danish Cardiac Arrest Registry

Abstract Background: to design and implement a new variable, in accordance with the Utstein style – namely the variable “AED” - considering the challenges of reporting cases in which the AED did not recommend an electrical shock after analyzing cardiac arrhythmias, for use in the Danish Cardiac Arrest Registry.Participants: Patients with out-of-hospital cardiac arrest for which resuscitation was attempted between 2016 and 2019, identified in the nationwide Danish Cardiac Arrest Registry. Their medical records were reviewed to establish a positive variable in “AED”.Methods: Data from the national Danish Cardiac Arrest Registry were used to identify core features of out-of-hospital cardiac arrests medical recording in Denmark and its possible improvement. Results: Among n= 1080 cases, summary statistics on core recording variables of interest were collected. We found statistically significant differences in the two cohorts of cardiac arrests where an AED was present on the scene and recorded in the Danish Cardiac Arrest Registry, regarding age, location, emeregency medical service response time, witnesses, bystander cardiopulmonary resuscitation, first monitored rhythm, direct current cardioversion shock delivered by the medical staff and survival outcomes such as return of spontaneous circulation at any time, status at arrival at hospital and 30-day survival. Conclusions: This validation study showed an improved completeness of registration of out-of-hospital cardiac arrests when implementing the new AED-variable, in accordance with the Utstein style. Thus, the new AED-variable is a valid and substantial resource for future epidemiological studies. However, a future effort to improve registration completeness along with continuous improvement of the Danish Cardiac Arrest Registry is needed.