Out-of-hospital cardiac arrest is a commonly encountered entity in U.S. emergency departments (EDs), with statistics reporting more than 356,000 out-of-hospital cardiac arrests per year.¹ Ventricular tachycardia (VT) and ventricular fibrillation (VF) represent the most common initial rhythms for patients presenting to the ED in out-of-hospital cardiac arrest, as well as for patients who develop cardiac arrest while in the ED.^2,3 In general, patients who develop cardiac arrest with an initial rhythm of VT or VF tend to have favorable outcomes compared to patients who develop cardiac arrest from either asystole or pulseless electrical activity.² Standard management for VT and VF involves the use of electrical defibrillation, high-quality chest compressions, and epinephrine. However, between four and five percent of cases of VT or VF will be refractory to standard management, with nonperfusing arrhythmia persisting despite repeated shocks.⁴ Given this, more recent attention has been paid to management of refractory VT and VF, with several recent updates suggesting new strategies that can be employed by emergency physicians for such cases.

What is “Refractory” VT/VF?

There are some differing guidelines as to what constitutes “refractory” VT or VF. Initial guidelines defined “refractory” as VT or VF occurring despite three shocks from a cardiac defibrillator.⁵ More recent literature defines “refractory” as VT or VF that is persistent or recurrent despite three shocks from a defibrillator, three rounds of epinephrine, and use of an antiarrhythmic (i.e., amiodarone or lidocaine).⁶

What Can I Do Outside of Repeated Shocks and Standard ACLS?

1. Change defibrillation strategy

Standard defibrillation uses pads in the anterolateral position. Modified strategies for refractory cases of VT or VF involve either moving the pads to the anteroposterior position or using two sets of pads for dual sequential external defibrillation. Prior retrospective reviews of dual sequential defibrillation showed promising results with regard to termination of refractory VF, return of spontaneous circulation, and survival to hospital discharge.⁸ More recently, the DOSE VF pilot study and subsequent cluster randomized control trial, Defibrillation Strategies for Refractory Ventricular Fibrillation, have demonstrated significant benefit of both anteroposterior pad placement and dual sequential defibrillation in cases of refractory VF compared to continued anterolateral shocks.^9,10

To perform dual sequence defibrillation, place pads in the anterolateral and anteroposterior position. One operator should perform defibrillation in the anterolateral position, followed by another operator providing a second shock in the anteroposterior position after a delay of less than one second.

Tips for use of dual sequence defibrillation¹¹:

• Use the same model of defibrillator.
• Pads need to be as close together as possible but not touching to avoid capacitor overload.
• Do not use synchronization.

2. Medications: think about using esmolol

Amiodarone has been traditionally used in the management of VT or VF as an adjunct to defibrillation. More recent literature and guidelines support the use of lidocaine as an alternative agent, and currently both are included in standard advanced cardiovascular life support .^12,13

Prior systematic reviews have looked at the use of beta blockade in the management of refractory VT or VF.¹⁴ A more recent review article looked at two retrospective studies with a combined total of 66 patients who were given esmolol in the treatment of refractory VT or VF.^6,15,16 These studies were small but did suggest significantly higher rates of return of spontaneous circulation in the esmolol group compared to standard care. There was insufficient data to suggest improvement in survival to discharge or degree of neurologic recovery. Proposed dosing for esmolol in the management of refractory VT or VF is 500 mcg/kg bolus, followed by a continuous infusion of up to 100 mcg/kg/min.

3. Extracorporeal membrane oxygenation

Of patients with out-of-hospital cardiac arrest presenting to the ED in refractory VF, a majority have significant coronary artery disease, much of which is amenable to percutaneous coronary intervention.^17,18 Given this, the advent of extracorporeal membrane oxygenation (ECMO) presents an opportunity to bridge care between traditional resuscitation of refractory VF patients in the ED and more definitive management in the catheterization lab. Post-resuscitation ECGs demonstrating ST segment elevation are significant in delineating which patients might benefit most from advanced reperfusion techniques.¹⁷ While previous evidence for the use of ECMO in refractory VF arrest has come from observational studies, the ARREST trial in 2020 represented the first open-label randomized trial evaluating the use of ECMO in the management of patients presenting to the ED in refractory VF arrest.¹⁸ This trial showed significant improvement in performance of patients treated with ECMO compared to standard care with regard to survival to hospital discharge, survival at six months, and overall functional outcome.¹⁹ Some aspects of the study, including rapid EMS response times and training as well as rapid time to cannulation, limit the generalizability of the data, but overall this study suggests significant promise in the use of ECMO for the management of this patient cohort.

Dr. Toomey (@DAVIDTOOMEYMD) is a senior instructor of Emergency Medicine at the University of Rochester Medical Center in Rochester, NY.

References

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