Double sequential external defibrillation (DSED) and vector change defibrillation have been proposed as viable options for patients in refractory ventricular fibrillation (VF) during out-of-hospital cardiac arrest. However, currently there is insufficient evidence to support widespread implementation of this therapy. As such, a well-designed randomized controlled trial (RCT) employing a standardized approach to alternative defibrillation strategies early in the treatment of refractory VF is required to determine whether these treatments may impact clinical outcomes. This cluster randomized trial will be conducted in the regions of Peel, Halton, Simcoe, and the cities of London, Ottawa, and Toronto, Ontario, Canada over a three year time period. All adult (≥ 18 years) patients presenting in refractory VF/pulseless ventricular tachycardia (pVT) (defined as patients presenting in VF/pVT and remaining in VF/pVT after three consecutive standard defibrillation attempts each separated by 2 minutes of CPR) during out-of-hospital cardiac arrest of presumed cardiac etiology will be assigned to be treated by one of three strategies: (1) continued resuscitation using standard defibrillation; (2) resuscitation involving DSED (two defibrillators, one using anterior-posterior pad placement and the second using anterior- anterior pad placement delivering two rapid sequential shocks for all subsequent defibrillation attempts); or (3) resuscitation involving vector change (change of defibrillation pads from anterior-anterior to an anterior-posterior pad position) defibrillation. All study arms will continue to receive antiarrhythmic use and epinephrine as per current provincial standards. The cluster units will be defined by emergency medical service (EMS) agency and each cluster will crossover at 6 month intervals throughout the duration of the study.
Despite significant advances in resuscitation efforts, there are some patients who remain in refractory ventricular fibrillation (VF) during out-of-hospital cardiac arrest. Double sequential external defibrillation (DSED) and vector change defibrillation have been proposed as viable options for patients in refractory VF. This cluster randomized trial will compare (1) continued resuscitation using standard defibrillation; (2) resuscitation involving DSED; or (3) resuscitation involving vector change defibrillation, in patients presenting with refractory VF during out-of-hospital cardiac arrest. The results of this study will provide high level evidence of the impact of both DSED and vector change defibrillation on ROSC and patient survival after OHCA.