VACEP's EBM Series: Defibrillation Strategies for Refractory Ventricular Fibrillation
VACEP Evidence-Based Medicine for General Emergency Physicians Series
Authors: Meghana Keswani, MD, PGY-3 & Joshua Easter, MD, MSc | UVA Health
Reviewer: Winston Wu, MD | UVA Health
The VACEP Evidence-Based Medicine review series highlights a recent peer-reviewed clinical study. You can also read the full article, Defibrillation Strategies for Refractory Ventricular Fibrillation | New England Journal of Medicine, November 6, 2022.
CASE
A 54-year old male with a history of coronary artery disease, diabetes mellitus, and hyperlipidemia is brought to the ED in by EMS in cardiac arrest. The patient had a witnessed arrest at home and his family started CPR. EMS intubated the patient and administered high quality CPR and 3 shocks en route for ventricular fibrillation. The patient’s rhythm at the next pulse check remains ventricular fibrillation.
So: What’s your plan?
STUDY SUMMARY
Nearly 350,000 people die annually from out of hospital cardiac arrest, and approximately one-third of those cases experience ventricular fibrillation or ventricular tachycardia (Go, 2013).
Despite significant advancements in cardiac arrest care, refractory ventricular fibrillation, where the rhythm persists despite three or more defibrillations over a six minute period, remains common during cardiac arrest. Unlike initial ventricular fibrillation, which has a good prognosis, refractory ventricular fibrillation is associated with decreased survival (Coult, 2023).
Figure 1. Pad Placement in the Three Defibrillation Strategies.
Pad placement for standard defibrillation, vector-change (VC) defibrillation, and double sequential external defibrillation (DSED) is shown. In the bottom panel, defibrillation pads 2A and 2B are those of the second defibrillator, with the pads placed in the posterior and anterior positions. For all strategies, the first three shocks occurred with pads placed in the configuration used for standard defibrillation.
Current American Heart Association’s (AHA) guidelines for ventricular fibrillation emphasize appropriate pad placement, early defibrillation, and providing high quality CPR. These guidelines do not address the option of vector change or dual sequential external defibrillation in patients who remain in cardiac arrest with refractory ventricular fibrillation.
Vector change with the pads placed anteriorly and posteriorly has the potential to improve energy delivery to the left ventricle, which is located posteriorly.
Double sequential defibrillation has the potential to increase the level of energy delivered to the heart.
Recently, the New England Journal of Medicine published a cluster randomized trial of 3 different defibrillation strategies for refractory ventricular fibrillation (Cheskes, 2022). This paper compared standard defibrillation, vector change defibrillation, and double sequential external defibrillation. Standard defibrillation was a typical attempt with pads placed in the anterior-lateral configuration (Figure 1).
Vector change defibrillation entails switching the pads from the anterolateral position to the anteroposterior position.
Double sequential external defibrillation entails the practice of providing rapid sequential defibrillations (spaced 1 second apart to avoid damaging the defibrillators) from two defibrillators with pads in two planes, anterolateral and anteroposterior.
Cheskes et al. randomized 405 patients seen by 6 paramedic services in Canada from 2018-2022 to these 3 different approaches.
The primary outcome was survival to hospital discharge and secondary outcomes were termination of ventricular fibrillation, return of circulation (ROC), and favorable neurological outcomes (measured by a modified Rankin score ≤2).
All patients had standard AHA protocols performed and received 3 defibrillation attempts in the standard method before being included. If the patient remained in either ventricular fibrillation or pulseless ventricular tachycardia after the 3 previous pulse checks/defibrillators, they were randomized to standard, vector controlled, or double sequential defibrillation.
Double sequential defibrillation was associated with improved survival to hospital discharge compared to standard defibrillation (RR=2.2; 95% CI: 1.3-3.7) as well as improved termination of ventricular fibrillation, ROC, and survival with favorable neurologic outcome (Table).
Vector change defibrillation was also associated with improved survival to hospital discharge compared to standard defibrillation albeit to a lesser extent (RR=1.7; 95% CI: 1.01-2.9). It was not significantly associated with improved ROC or survival with favorable neurologic outcome (Table).
Groups were well matched for potential confounders, such as the quality of CPR provided, timing of drug administration, and the mean doses of drug utilized.
Table
About the EBM Review Series
This is a literature review series started by the University of Virginia’s Josh Easter, MD, MSc, a VACEP board member working to connect the academic community in Virginia. We invite each residency in Virginia (and D.C.) to create a faculty/resident team to submit and review articles. Sign up to submit one.
Goals
Provide a brief monthly synopsis of a high yield article germane to the practice of emergency medicine for distribution to all VACEP members
Provide an opportunity for a peer reviewed publication and invited presentation for faculty and trainees
Foster an academic community focused on evidenced based medicine for emergency medicine residency programs in the region
ANALYSIS
This is the first randomized control trial to show that double sequential defibrillation can improve outcomes, including survival, when implemented early in the resuscitation process as opposed to as a final resort.
The result was so impressive that it reached significance, despite needing to terminate the trial early due to Covid-19. This is powerful, as most interventions for patients in cardiac arrest do not improve mortality.
The primary limitation is that this study was conducted in the pre-hospital setting. While the results likely extend to the ED, this was not directly studied.
Nevertheless, the findings appear to have significant implications in the ED and pre-hospital settings, and this novel approach should be employed for patients where standard defibrillation has not succeeded. It also seems appropriate to employ the vector change approach initially for single defibrillation with pads placed anterior and posterior instead of anterior and lateral.
Conclusion
You have a second defibrillator in the room on patient arrival and place the ED pads in the anteroposterior position. At the next pulse check, the patient remains pulseless and in ventricular fibrillation. You and EMS perform double sequential external defibrillation. This results in return of circulation at the next pulse check, and the patient is subsequently admitted to the ICU, where they experience a good neurologic recovery.
