BACKGROUND: Valuable information can be retrieved from automated external defibrillators (AEDs) used in victims of out-of-hospital cardiac arrest (OHCA). We describe our experience with systematic downloading of data from deployed AEDs. The primary aim was to compare the proportion of shockable rhythm from AEDs used by laypersons with the corresponding proportion recorded by the Emergency Medical Services (EMS) on arrival.

METHODS: In a 20-month study, we collected data on OHCAs in the Capital Region of Denmark where an AED was deployed prior to arrival of EMS. The AEDs were brought to the emergency medical dispatch centre for data downloading and rhythm analysis. Patient data were retrieved from the medical records from the admitting hospital, whereas data on EMS rhythm analyses were obtained from the Danish Cardiac Arrest Register between 2001 and 2010.

RESULTS: A total of 121 AEDs were deployed, of which 91 cases were OHCAs with presumed cardiac origin. The prevalence of initial shockable rhythm was 55.0% (95% CI [44.7-64.8%]). This was significantly greater than the proportion recorded by the EMS (27.6%, 95% CI [27.0-28.3%], p<0.0001). Shockable arrests were significantly more likely to be witnessed (92% vs. 34%, p<0.0001) and the bystander CPR rate was higher (98% vs. 85%, p=0.04). More patients with initial shockable rhythm achieved return of spontaneous circulation upon hospital arrival (88% vs. 7%, p<0.0001) and had higher 30-day survival rate (72% vs. 5%, p<0.0001).

CONCLUSION: AEDs used by laypersons revealed a higher proportion of shockable rhythms compared to the EMS rhythm analyses.