Variations of shock efficacy and refibrillation in different AED user groups

Area of Science:

• Cardiology
• Emergency Medicine
• Biomedical Engineering

Background:

• Automated external defibrillator (AED) use in out-of-hospital cardiac arrest (OHCA) is critical, with outcomes influenced by user type and time to shock.
• Understanding variations in AED shock efficacy and refibrillation rates across different user groups is essential for improving survival rates.

Purpose of the Study:

• To compare the shock efficacy and refibrillation rates of AEDs used by lay responders, trained first responders, and emergency medical services (EMS).
• To analyze factors influencing AED outcomes, including amplitude spectrum area (AMSA) and shock impedance.

Main Methods:

• Analysis of ECG data from 2358 adult OHCA cases in the US and Europe using three AED models (HS1, FRx, FR3).
• Grouping cases by AED user: lay-responder (HS1), trained first-responder (FRx), and EMS (FR3).
• Comparison of shock success and refibrillation rates, with regression analyses for AMSA and shock impedance associations.

Main Results:

• Overall shock efficacy was highest in lay-responders (95.0%), followed by trained first-responders (94.0%), and EMS (86.6%) (p < 0.001).
• First shock efficacy also favored lay-responders (96.9%) over trained first-responders (94.5%) and EMS (89.0%) (p = 0.007).
• Refibrillation rates varied significantly (p = 0.016), with higher AMSA associated with reduced refibrillation (HR, 0.95). Shock impedance did not correlate with efficacy or refibrillation.

Conclusions:

• Low-energy biphasic shocks from AEDs are highly effective across various user scenarios, independent of shock impedance.
• Lay responders demonstrated superior shock efficacy and lower refibrillation rates compared to trained first responders and EMS, potentially due to shorter response times.
• While AMSA influences refibrillation, other factors likely contribute to observed differences in AED outcomes among user groups.