Abstract 2625: A Measure of the Ventricular Fibrillation Waveform to Guide Care before the Initial Shock
Background: Optimal treatment for out-of-hospital ventricular fibrillation (VF) cardiac arrest is uncertain. Initial shock may provide best chance of survival for some, while for others better survival might be achieved if shock were delayed until therapies such as CPR could be provided. We evaluated whether a measure of VF waveform could discriminate survival, and compared the potential impact of strategies using VF waveform versus emergency medical services (EMS) response intervals to guide initial shock.
Hypotheses: Compared to EMS response interval, a measure of VF waveform prior to initial shock better discriminates survival.
Methods Design, setting, and population- Cohort study of persons ≥ 18 years suffering VF arrest treated with ForeRunner AED by an EMS system using a shock-first protocol (n=129). Exposure: Quantitative VF measure that incorporates amplitude and frequency upon initial AED application. Two commercially-available thresholds for the VF waveform (VF1 and VF2) were compared to EMS response intervals of 6 and 5 minutes respectively. Outcome -Neurologically-intact hospital survival. Analyses- We used chi-squared statistic to compare the proportion with neurologically-intact survival whose care would change using VF1 and VF2 versus EMS response interval.
Results: Neurologically-intact survival was 26.0% (33/129) overall. Using the VF1 threshold, care would change for 25% (32/129) of whom none (0/32) survived under the shock-first protocol (Table⇓). Using the VF2 threshold, care would change for 37% (48/129) of whom 2% (1/48) survived under the shock-first protocol. Although EMS interval could be used to change care in similar numbers, those affected included a greater proportion of survivors of the shock-first approach (7/35 and 10/59, p < 0.05 compared with VF threshold).
Conclusion: A measure of VF waveform discriminated neurologically-intact survival better than EMS interval and has potential to guide care and improve outcome.