Is earlier better? Re-examining the timing of double sequential external defibrillation

Defibrillation remains the cornerstone of resuscitation for patients suffering cardiac arrest who present in ventricular fibrillation (VF). It continues to represent one of the few Class I recommendations endorsed by both the European Resuscitation Council and the American Heart Association.1 2 Despite important advances in defibrillator technology, waveform optimisation and resuscitation systems of care, a sobering reality persists: nearly half of all patients in VF require more than three defibrillation attempts.3 How best to manage this challenging subgroup, those with shock-refractory VF, remains an area of ongoing evolution and intense interest within the resuscitation community. The publication of the Double Sequential External Defibrillation for Refractory Ventricular Fibrillation (DOSE VF) trial in 2022 marked a pivotal moment, challenging longstanding assumptions regarding optimal defibrillation strategies. In this cluster-randomised crossover trial, the use of double sequential external defibrillation (DSED), applied after three failed standard shocks, resulted in more than a doubling of survival to hospital discharge and neurologically intact survival when compared with continued standard defibrillation.4 These findings were both striking and practice-informing. Complementary research has consistently demonstrated a strong association between total time spent in VF and the likelihood of neurologically intact survival.5 Importantly, strategies incorporating DSED appear to reduce cumulative time in VF relative to conventional approaches, providing a plausible mechanistic explanation for the observed benefit.6 These observations naturally lead to a critical and as yet unanswered question: if DSED is superior once VF becomes refractory after three shocks, why should clinicians wait until the fourth shock to introduce it? In other words, could earlier implementation of DSED further improve outcomes by shortening time in VF and increasing the likelihood of successful defibrillation at an earlier stage of resuscitation?