Introduction: Despite recent advances in resuscitation, some patients remain in ventricular fibrillation (VF) after multiple defibrillation attempts during out-of-hospital cardiac arrest (OHCA). Vector change defibrillation (VC) and double sequential external defibrillation (DSED) have been proposed as alternate therapeutic strategies for OHCA patients with refractory VF. The primary objective was to determine the feasibility, safety and sample size required for a future cluster randomized controlled trial (RCT) with crossover comparing VC or DSED to standard defibrillation for patients experiencing refractory VF. Secondary objectives were to evaluate the intervention effect on VF termination and return of spontaneous circulation (ROSC). Methods: We conducted a pilot cluster RCT with crossover in four Canadian paramedic services and included all treated adult OHCA patients who presented in VF and received a minimum of three defibrillation attempts. In addition to standard cardiac arrest care, each EMS service was randomly assigned to provide continued standard defibrillation (control), VC or DSED. Services crossed over to an alternate defibrillation strategy after six months. Prior to the launch of the trial, 2,500 paramedics received in-person training for VC and DSED defibrillation using a combination of didactic, video and simulated scenarios. Results: Between March 2018 and September 2019, 152 patients were enrolled. Monthly enrollment varied from 1.4 to 6.1 cases per service. With respect to feasibility, 89.5% of cases received the defibrillation strategy they were randomly allocated to, and 93.1% of cases received a VC or DSED shock prior to the sixth defibrillation attempt. There were no reported cases of defibrillator malfunction, skin burns, difficulty with pad placement or concerns expressed by paramedics, patients, families, or ED staff about the trial. In the standard defibrillation group, 66.6% of cases resulted in VF termination, compared to 82.0% in VC and 76.3% of cases in the DSED group. ROSC was achieved in 25.0%, 39.3% and 40.0% of standard, VC and DSED groups, respectively. Conclusion: Findings from our pilot RCT suggest the DOSE VF protocol is feasible and safe. VF termination and ROSC were higher with VC and DSED compared to standard defibrillation. The results of this pilot trial will allow us to inform a multicenter cluster RCT with crossover to determine if alternate defibrillation strategies for refractory VF may impact patient-centered, clinical outcomes

Introduction: Despite significant advances in resuscitation efforts, there are some patients who remain in ventricular fibrillation (VF) after multiple shocks during out-of-hospital cardiac arrest (OHCA). Double sequential external defibrillation (DSED) has been proposed as a treatment option for patients in shock refractory VF. We sought to compare DSED to standard therapy with regards to VF termination and return of spontaneous circulation (ROSC) for patients presenting in shock refractory VF. Methods: We performed a retrospective review of all treated adult OHCA who presented in VF and received a minimum of three successive shocks over a two year period beginning on Jan 1, 2015 in four Canadian EMS agencies. Using ambulance call reports and defibrillator files, we compared VF termination (defined as the absence of VF at the rhythm check following defibrillation and 2 minutes of CPR) and VF termination into a perfusing rhythm with ROSC between patients who received standard therapy (CPR, defibrillation, epinephrine and antiarrhythmics) and those who received DSED (after on-line medical consultation) for shock refractory VF. Cases of traumatic cardiac arrest and those who presented in VF but terminated VF prior to 3 successive shocks were excluded. Results: Among 197 patients who met the study criteria for shock refractory VF, 161 (81.7%) patients received standard therapy and 36 (18.3%) received DSED. For the primary outcome, VF termination was significantly higher for DSED compared to standard therapy (63.9% vs 18.0%; Δ45.9%; 95% CI: 28.3 to 60.5). For the secondary outcome of VF termination into ROSC, DSED was associated with significantly higher ROSC compared to standard care (33.3% vs 13%; Δ20.3%; 95% CI:13.0 to 33.3). The median (IQR) number of failed standard shocks prior to DSED was 8 (6, 10). When DSED terminated VF, it did so with a single DSED shock in 69.6% of cases. Conclusion: Our observational findings suggest improved VF termination and ROSC are associated with DSED compared to standard therapy for shock refractory VF. An appropriately powered randomized controlled trial is required to assess the impact of DSED on patient-important outcomes.

Dual sequential external defibrillation (DSED) is the process of near simultaneous discharge of two defibrillators with differing pad placement to terminate refractory arrhythmias. Previously used in the electrophysiology suite, this technique has recently been used in the emergency department and prehospital setting for out-of-hospital cardiac arrest (OHCA). We present a case of successful DSED in the emergency department with neurologically intact survival to hospital discharge after refractory ventricular fibrillation (RVF) and review the putative mechanisms of action of this technique.