Objective: To describe survival rates from out-of-hospital cardiac arrest for patients who present with pulseless electrical activity or asystole according to whether they remained in a non-shockable rhythm or converted to ventricular fibrillation and were shocked appropriately.
Results: Observational analysis of a cardiac arrest registry collected as part of a randomized trial.
Setting: Five urban/suburban cities in the United States and Canada.
Participants: Trial subjects (adult, treated, non-traumatic) whose first documented heart rhythm/state following cardiac arrest was asystole or pulseless electrical activity.
Intervention: Periodic pauses to assess for shockable rhythm.
Main outcome measure: Survival to hospital discharge.
Results: Of 1377 cardiac arrest patients, 738 presented with an initial arrest rhythm/state of either pulseless electrical activity or asystole. Of the 738, 78% (n=574) subsequently remained in a non-shockable rhythm/state at each evaluation throughout the resuscitation (No-Shock group) while 22% (n=164) converted to ventricular fibrillation and were shocked by emergency medical service (Shock group). Survival to hospital discharge was significantly greater in the No-Shock group (4.9% versus 0.6%, p=0.01). Shock group remained a predictor (odds ratios=0.18, p=0.036) of death after adjustment for potential confounders.
Conclusions: These results suggest that patients with cardiac arrest who develop VF during the course of treatment for initially observed pulseless electrical activity or asystole do not benefit from conventional approaches to treatment such as defibrillation. Further study is warranted to define the optimal treatment of this patient cohort.