A comparison of the epidemiology and outcomes of true refractory and recurrent ventricular fibrillation out-of-hospital cardiac arrest: a retrospective study

To explore and compare patient characteristics and clinical outcomes across true-refractory and recurrent VF/pVT cases, at two commonly used time points, including after the first and third consecutive shocks. We performed a retrospective analysis of adult (≥16 years old) out-of-hospital cardiac arrest (OHCA) patients with initially shockable rhythms and complete defibrillator recordings between January 2019 and October 2022. Defibrillator recordings were reviewed using standardised criteria to classify patients into true-refractory VF/pVT, defined as persistent VF/pVT 5 seconds after shock delivery, and recurrent VF/pVT, defined as termination of arrhythmia at 5 seconds post-shock followed by recurrence at the end of the 2-minute CPR cycle. Multivariable logistic regression was used to examine the impact of true-refractory VF/pVT on survival outcomes and to identify factors associated with true-refractory VF/pVT. Of the 2,343 cases with complete defibrillator recordings, 1,880 cases met the inclusion criteria. The incidence of true-refractory VF/pVT declined with increasing defibrillation attempts, accounting for 28.9%, 5.0%, and 1.0% of cases after the first, third and fifth consecutive shocks, respectively. Compared to patients with recurrent VF/pVT, true-refractory VF/pVT was associated with lower odds of survival to hospital discharge (adjusted odds ratio (AOR) 0.45, 95% CI: 0.22–0.92; p=0.029) and pre-hospital ROSC (AOR 0.58, 95% CI: 0.36–0.95; p=0.029). Older age and prolonged resuscitation were associated to true-refractory cases. Although associated with substantially worse outcomes, true-refractory VF/pVT is a time-limited condition which typically responds to repeated defibrillation attempts. Further research is needed to determine whether earlier recognition and optimal management of true-refractory VF/pVT can improve outcomes.