'Reply to:' Importance of the distinction between recurrent and shock-resistant ventricular fibrillation: Call for a uniform definition of refractory VF

摘要

We thank Nas and colleagues for their interest in our work and acknowledge the lack of a uniform definition for refractory or shock-resistant ventricular fibrillation (VF). Although refractory VF refers to persistent VF that fails to respond to at least three defibrillation attempts, the condition is typically self-reported by rescuers and is often not verified using electrocardiogram records. In comparison, recurrent VF occurs when defibrillation successfully terminates VF, only to recur rapidly and usually within two minutes of shock delivery. As CPR is commenced immediately after a shock is delivered, recurrent VF often goes unrecognised by rescuers due CPR artefact on the monitor. Indeed, both of the observational studies included in our meta-analysis are at risk of unknowingly including episodes of recurrent VF. Neither study reported having reviewed electrocardiogram records to verify the condition and this resulted in a downgrading of their methodological quality. Although we attempted to perform a sub-analysis of cases defined solely as refractory VF, it is possible that both studies are contaminated with a number of recurrent VF cases which could influence the direction and magnitude of benefit of double sequential external defibrillation (DSED). Importantly, recurrent VF could be as much as seven times more prevalent than refractory VF in patients with an initial VF arrest.