A One-Two Punch: Double Sequential Defibrillation for Refractory Cardiac Arrest

An 81-year-old woman in ventricular fibrillation refractory to six shocks. A 47-year-old man, ditto. A woman of just 27, same condition, unconverted after four.

These patients had two things in common: One, they received EMS care in Multnomah County, Oregon. Two, they survived their persistent cardiac arrests and lived to hospital discharge—thanks in large part to the rare but potentially lifesaving practice of double-sequential defibrillation. 

It’s an idea that first came to American EMS in Wake County, NC (see www.emsworld.com/10318805) and is now practiced by a handful of major systems. It involves, for those patients you just can’t get back, using two AEDs in fast succession to deliver a large last-gasp jolt to the heart before ending resuscitation efforts.

The numbers aren’t huge, but in Multnomah, as it has elsewhere, the practice has salvaged some refractory VF/VT victims who might otherwise have been terminated in the field.

“There is precedent for this in the cath lab, and preliminary reports have been very promising,” says Jon Jui, MD, MPH, the county’s EMS medical director and a professor in the department of emergency medicine at Oregon Health & Science University. “There’s always a concern of doing harm with higher electrical voltages and energy. But in this case the alternative is, they’re dead.”

Ending the Electrical Storm

Jui presented two years’ worth of data from his system’s use of DSD (which is modeled on Wake County’s protocol) at February’s Gathering of Eagles conference.

In Oregon a total of 26 patients met the threshold for double defib (refractory to five or more shocks; administered 450 mg of amiodarone; VF/VT that never converted). Of those, 16 attempts (54%) were unsuccessful; 12 (46%) achieved electrical success, or conversion to an organized rhythm; and 9 (34%) reached ROSC. Three survived. That’s a rate of 11.5%—not bad for a group that otherwise likely would have cashed out.

“The dilemma we have in EMS is that a certain proportion of our patients in ventricular fibrillation—up to 10%—are nonremediable to shock,” says Jui. “We became aware of the experiences in Wake and with some of our other Eagles colleagues, and so we approached our cardiologists and found they were using double sequential for atrial fibrillation in the laboratory as well. So we thought it was a viable option, especially with the case reports from Wake and other communities.”

Indeed, in the cardiology world, this isn’t a new idea. Literature on it goes back to the 1980s, and in 1994 a team led by New York cardiologist David Hoch found the “technique of rapid double sequential external shocks may have general applicability, providing a simple and potentially lifesaving approach to refractory ventricular fibrillation.”¹

Jui also cited some more recent work:

• A team led by Wake County EMS director/medical director Jose Cabanas, MD, MPH, produced a retrospective case series in 2015 that reviewed 10 patients who received double shocks. That broke their v-fib in seven of 10 cases. However, only three patients had ROSC in the field, and none made it to hospital discharge.²
• That same year authors led by New Mexico anesthesiologist Neal Gerstein, MD, reported a 66-year-old man who regained ROSC after two double-dose defibrillations following 72 minutes of refractory VF. He also didn’t survive, however.³
• St. Louis emergency physician Aurora Lybeck, MD, reported on a 40-year-old male refractory to seven shocks who was converted by an eighth that used two defibrillators. He recovered and was sent home with a CPC of 1.⁴ 

Of course double-sequential defibrillation isn’t a magic bullet; treating cardiac arrestees still requires our full systemic complement of ACLS best practices.

“We don’t believe this is the be-all, end-all,” emphasizes Jui. “I think when you have cardiac arrest, there are two or three underlying etiologies to highlight. One is that refractory electrical arrest is probably caused by electrolyte imbalance, cardiac arrhythmia or some other reason where there’s no native ischemia to the heart. It’s really an electrical storm, so to speak. And with ischemia, it’s like an acute coronary MI or something causing irritation and refractory to our normal modalities. In that case, treatment usually is the cath lab and opening up the blocked artery. So one of those two options is usually involved as well.”

Why does double defib sometimes work? That we still don’t know. It may be a function of vector, i.e., placement of the pads. Says Jui: “There has been animal work suggesting the more you depolarize the ventricular septum, the better the possibility of the shock working.” In this case AP pad placement may provide an advantage.

It may be a function of duration or energy, i.e., the prolonged current or total joules coming from two defibrillators fired as synchronously as possible. “When you’re defibrillating a patient,” says Jui, “you’re trying to reset all the myocytes into a certain cardiac rhythm. It may be that to reset all the myocytes, the duration of the shock, as well as the energy supply, is important.

“The easy explanation is using more energy, but you’re using a better space defibrillation sequence as well, and you’re actually using a better vector.”

Use of the protocol continues in Multnomah County, and there’s a hope to combine the case data from Oregon, Wake County and other systems using it for a broader look.

Meanwhile, systems may want to consider it as a way to shave down a fatality rate for refractory VF/VT that’s pretty dreadful.

“It’s unproven science, but the preliminary results are good,” says Jui. “Keep in mind that it requires a fairly coordinated system, and five [shocks] was completely arbitrary as well.

“Field personnel need to understand the big picture, which is that refractory v-fib probably needs two measures. One is an EMS measure such as double-sequential defibrillation. The second one is likely a cardiac cath measure. So this is not a one-shot deal. It’s a therapeutic scheme where we’re trying to identify the best practice.”

References

1. Hoch DH, Batsford WP, Greenberg SM, et al. Double sequential external shocks for refractory ventricular fibrillation. J Am Coll Cardiol, 1994 Apr; 23(5): 1,141–5.

2. Cabañas JG, Myers JB, Williams JG, De Maio VJ, Bachman MW. Double sequential external defibrillation in out-of-hospital refractory ventricular fibrillation: a report of ten cases. Prehosp Emerg Care, 2015 Jan–Mar; 19(1): 126–30.

3. Gerstein NS, Shah MB, Jorgensen KM. Simultaneous use of two defibrillators for the conversion of refractory ventricular fibrillation. J Cardiothorac Vasc Anesth, 2015 Apr; 29(2):421–4.

4. Lybeck AM, Moy HP, Tan DK. Double sequential defibrillation for refractory ventricular fibrillation: a case report. Prehosp Emerg Care, 2015; 19(4): 554–7.