Double sequential external defibrillation for refractory ventricular fibrillation: the science, the controversies and the future.

Double sequential external defibrillation (DSED), the technique of providing two rapid shocks from two defibrillators with pads placed in the anterior-lateral and anterior-posterior position has been studied in animal labs and clinical practice for over two decades. In 2022, the Double Sequential External Defibrillation for Refractory Ventricular Fibrillation (DOSE-VF, clinicaltrials.gov: NCT04080986) trial was published in the New England Journal of Medicine. This cluster randomized crossover trial involved six paramedic services in Ontario, Canada, and compared standard (anterior-lateral) defibrillation to vector change defibrillation (VC, anterior-posterior pad repositioning) or DSED for patients with ventricular fibrillation (VF) and unresponsive to three standard shocks. The trial showed superior outcomes for all primary and secondary endpoints (VF termination, return of spontaneous circulation [ROSC], survival to hospital discharge, and neurologically intact survival) with DSED versus standard defibrillation, and improved VF termination and survival to discharge, but not ROSC or neurologically intact survival, with VC versus standard defibrillation. These findings, along with the 2023 updated ILCOR guidelines endorsing DSED for refractory VF, have generated significant global interest in it's implementation. This manuscript explores the scientific rationale and underlying mechanisms of DSED, examines controversies surrounding its implementation, and outlines directions for future research.