Time to first defibrillation and survival outcomes of out-of-hospital cardiac arrest with refractory ventricular fibrillation.

INTRODUCTION

Timely defibrillation is associated with increased survival in out-of-hospital cardiac arrest (OHCA) cases. This study aimed to determine whether the time to first defibrillation was associated with good neurological outcomes in OHCA patients with refractory ventricular fibrillation.

METHODS

Bystander-witnessed adult OHCA patients with presumed cardiac etiology who presented with ventricular fibrillation and received ≥2 successive prehospital defibrillations from emergency medical services between 2013 and 2018 were included. The times from collapse to first defibrillation were categorized into Group 1 (0-5 min), Group 2 (6-10 min), Group 3 (11-15 min), and Group 4 (16-60 min). The primary outcome was a good neurological recovery (cerebral performance category 1-2). Multivariable logistic regression analysis was performed to calculate the adjusted odd ratios (AORs) and 95% confidence intervals (CIs) for outcomes according to time group (Group 1 as the reference) and per 1-min delay.

RESULTS

The study included 5753 patients, with overall rates of 34.4% for survival to discharge and 27.2% for good neurological recovery. The median number of prehospital defibrillations was 3 (interquartile range 2-5). Relative to Group 1, the AORs for good neurological recovery were 0.58 in Group 2 (95% CI: 0.41-0.82), 0.42 in Group 3 (95% CI: 0.29-0.60), and 0.19 in Group 4 (95% CI: 0.13-0.29). When time from collapse to first EMS defibrillation was analyzed as a continuous variable, each 1-min delay was associated with a significant decrease in the likelihood of good neurological recovery (AOR: 0.93, 95% CI: 0.91-0.94).

CONCLUSIONS

A short time from collapse to first defibrillation was associated with good neurological recovery among patients with OHCA and refractory ventricular fibrillation. This result suggests that a failed first shock still has a positive effect if it is delivered quickly.