A Better Way to Defibrillate Patients In Cardiac Arrest?

I have taken the American Heart Association’s Advanced Cardiac Life Support (ACLS) certification/recertification course every 2 years since 1983. That’s 20 times since medical school. The resuscitation algorithms have changed dramatically over the past 39 years and based on a new study, it may be time to change them once again.

In 1984, every patient in ventricular ventricular fibrillation got lidocaine and sodium bicarbonate as first line medications. The second line antiarrhythmics were quinidine, procainamide, and bretylium. Amiodarone was not yet in use. The current ACLS algorithm for ventricular fibrillation is much simpler. In addition to CPR, patients receive electrical defibrillation every 2 minutes, epinephrine every 3-5 minutes, and amiodarone if sinus rhythm is not restored within the first 6 minutes.

For decades, defibrillation has consisted of placing 2 electrode pads on the patient’s chest – one just below the right clavicle and the other just below and lateral to the left nipple. Then, a single shock of 300 or 360 joules is delivered followed by resumption of chest compressions. A new Canadian study published in the New England Journal of Medicine suggests that there may be a better way to do electrical defibrillation. In the study, 405 patients with out-of-hospital cardiac arrest with refractory ventricular fibrillation were randomly assigned to receive one of three different defibrillation techniques. All patients had an initial three defibrillation attempts using standard defibrillation technique with each attempt occurring 2 minutes after the previous attempt. Patients remaining in ventricular fibrillation were considered to have refractory ventricular fibrillation and were eligible for inclusion in the study. The three salvage defibrillation techniques consisted of (1) standard defibrillation, (2) vector-change defibrillation, or (3) double-sequential external defibrillation.

1. For standard defibrillation, the electrode pads are located in the traditional locations: one pad below the right clavicle and the other pad on the lateral part of the left chest, just below the left nipple. After the initial 3 defibrillation attempts, all additional attempts occurred with with the pads located in their original position.
2. For vector-change defibrillation, the pads were re-located with one pad on the anterior chest just below the left nipple and the other pad on the posterior chest, just below the scapula and just left of the spine.
3. For double-sequential external defibrillation, the two standard pads are left in place and two additional pads are placed with one pad on the anterior chest between the sternum and the left nipple and the other pad on the posterior chest, just below the scapula and left of the spine. With this technique, 2 shocks are delivered within 1 second of each other with the first shock via the anterior/lateral pads (in red on the adjacent figure) and the second shock via the anterior posterior pads (in blue on the adjacent figure).

The primary outcome of the study was survival to hospital discharge and the findings were statistically significant. For patients receiving salvage defibrillation via the standard technique, only 13.3% survived to hospital discharge. For those receiving salvage defibrillations via the vector-change technique, 21.7% survived to hospital discharge. And for those receiving salvage defibrillations via the double-sequential external defibrillation technique, 30.4% survived to hospital discharge. The double-sequential external defibrillation was also superior to the other techniques in terminating defibrillation, achieving return-of-spontaneous-circulation, and modified Rankin scale score (a measure of neurologic disability).

As with all clinical trials, there are limitations to the study. It included only out-of-hospital cardiac arrest patients so it is not clear whether similar results would be achieved in patients arresting in the hospital. It was not a blinded study so it is possible that the EMS personnel could have had unconscious bias in their resuscitation efforts. The number of patients was relatively small so it is possible that larger studies may not achieve the same results. The post-arrest care received in the hospitals was not protocoled so there may be differences in targeted-temperature management, cardiac catheterization management, sedation, mechanical ventilation, etc. Because all patients had 3 initial attempts at standard defibrillation before randomization, it is unclear whether either vector-change defibrillation or double-sequential external defibrillation is superior to standard defibrillation as an initial defibrillation technique. Lastly, it is unclear whether the results can be extrapolated to other tachyarrhythmias such as ventricular tachycardia, atrial fibrillation, or supraventricular tachycardia.

Implication for hospital care

So, what does this mean for physicians responding to cardiac arrests in the emergency department, intensive care unit, and hospital nursing units? It is unlikely that the American Heart Association will change the ACLS algorithm for ventricular fibrillation management in the immediate future. However, the study does at least indicate that when patients do not respond to initial defibrillation efforts, we have two other options that we can try.

Vector-change defibrillation is the easiest technique to implement since it simply requires moving the existing defibrillator pads to different locations. Double-sequential external defibrillation may be more challenging for hospitals to implement since it requires the use of a second defibrillator. In addition, although vector-change defibrillation can be performed using an automated external defibrillator (AED), double-sequential external defibrillation cannot be performed using an AED.

When a patient is in refractory cardiac arrest and is not responding to usual advanced cardiac life support measures, physicians may find themselves in a position of having nothing to lose by trying alternative defibrillation techniques. In this situation, vector-change defibrillation or double-sequential external defibrillation may be worth a try.

November 28, 2022