Clinical state transitions in shock-refractory ventricular fibrillation: an observational study

To characterise clinical state transitions in patients with out-of-hospital cardiac arrest (OHCA) from refractory ventricular fibrillation or pulseless ventricular tachycardia (VF/pVT) and their association with clinical outcomes.

We conducted an exploratory observational study of refractory VF/pVT OHCA cases treated by emergency medical services (EMS) between 2010 and 2019 in Victoria, Australia. Refractory VF/pVT OHCA was defined as initial VF/pVT arrests with at least three consecutive defibrillation attempts. Adjusted logistic regression analyses were conducted to examine predictors of clinical state transitions and secondary VF/pVT.

3,018 cases met the inclusion criteria. Of these, 35.8% transitioned into ROSC, 36.6% transitioned into PEA, and 17.5% transitioned into asystole. secondary VF/pVT occurred in 41.7% of patients. The proportion of patients discharged alive was significantly higher in the ROSC group (60.0%) compared to the PEA (11.3%) and asystole groups (3.2%). Predictors of achieving ROSC included being witnessed by bystanders or EMS and bystander CPR. Predictors of secondary VF/pVT included male gender, increased resuscitation duration and administering adrenaline prior to the first clinical state transition. Transitioning into ROSC was associated with reduced odds of secondary VF/pVT, while transitioning into PEA increased the odds of secondary VF/pVT.

Understanding clinical state transitions during the resuscitation of refractory VF/pVT patients may allow for the development of tailored treatment strategies.