Does transthoracic impedance influence termination and recurrence of ventricular fibrillation during impedance-compensated shocks for out-of-hospital cardiac arrest? A retrospective study

AIM: To examine the association between transthoracic impedance (TTI) and termination of ventricular fibrillation or pulseless ventricular tachycardia (VF/pVT) and recurrent VF/pVT in out-of-hospital cardiac arrest (OHCA). METHODS: We conducted a retrospective observational study of non-traumatic OHCA in patients aged ≥16 years with an initial shockable rhythm between January 2019 and October 2022. Termination of VF/pVT was defined as the absence of a shockable rhythm within 5 s following shock delivery, resulting in asystole or an organised rhythm. The relationship between TTI and VF/pVT termination and recurrence were assessed using mixed-effects logistic regression models applied to shock level data with a random intercept for clustering by patient. RESULTS: Between 2019 and 2022, 1880 cases met the inclusion criteria, comprising 8333 analysable shocks. The unadjusted probability of VF/pVT termination declined at TTI values ≥100 Ω, whereas no clear relationship was observed at TTI