Double Sequential Defibrillation

DSD was first described in human subjects in 1994 when it was used to successfully defibrillate five patients who entered rVF during routine electrophysiologic testing. These patients were otherwise refractory to between seven and twenty single shocks. Looking at the available literature there has been little interest in DSD since then, until the last two to three years when it appears to have undergone a small revival. Sadly, there is no evidence for its use beyond case reports and small case series.

The case reports appear to show good results with four in the last two years reporting survival to discharge with good neurological outcome. There are also a handful of other cases discussed in online blogs and articles with good outcomes. But these case reports and articles almost certainly represent an excellent example of publication bias. The most recent case series reviewed the use of DSD by an American ambulance service over a period of four years. During this time DSD was written into their refractory VF protocol, with rVF defined as failure of five single shocks. The study included twelve patients, three of whom survived to discharge with two of these demonstrating a cerebral performance score of 1. Despite appearing to demonstrate reasonable outcomes for DSD, sadly this study has a number of significant limitations. One important point the authors fail to discuss is that the two neurologically intact survivors received their DSD shocks after two and three single shocks respectively, not after five shocks which would have been per-protocol and consistent with the authors definition of refractory VF.

This highlights a further problem with analysing the use of DSD. Not only is there a dearth of high-level evidence, but the literature that is available is highly inconsistent. There are a range of definitions for refractory VF, different orientations for the second set of pads, variable interventions prior to using DSD, a variety of timings between the shocks and so on. This means that comparison between studies and drawing meaningful conclusions is nearly impossible. Given these challenges, what are the explanations for why DSD might work?

The first theory is that by using DSD the myocardium is defibrillated with a broader energy vector compared to a single set of pads resulting in a more complete depolarisation of the myocardium. A second theory is that the first shock reduces the ventricular defibrillation threshold meaning that the second shock is more effective. A third explanation may simply be the large amount of energy delivered to the myocardium. These theories should be tempered by the fact that studies have demonstrated increasing defibrillation energy to result in increased defibrillation success, but only up to a plateau. After this the success of defibrillation drops sharply. Increased energy use has also been demonstrated to cause an increase in A-V block but without an associated increase in shock success or patient outcome.

The use of double sequential defibrillation is clearly an area that would benefit from further research, but despite this it is interesting to note that London Ambulance Service have enabled their Advanced Paramedic Practitioners to use DSD and some American EMS systems have written DSD into their protocols.

So returning to the case in point what did I choose to do with my patient?

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After changing the pad position, administering magnesium and continuing defibrillation they remained in VF.  I considered transport to a hospital with interventional cardiology but the patient was several stories up in a property with an inherently complex extrication. So I chose to use DSD because I felt that all other avenues had been explored. The patient had suffered a witnessed arrest, received bystander CPR immediately and throughout the resuscitation they had maintained a high end tidal CO2 and a coarse VF. I felt that this was a patient who could still respond to non-standard cardiac arrest management in the absence of a response to guideline directed treatment. After two DSD shocks a return of spontaneous circulation was achieved and the patient survived to hospital admission, but sadly didn’t survive to hospital discharge.

We’re left with a even bigger question: if we accept that DSD is a potentially useful intervention in rVF, when should we consider using it? Would the outcome for this patient have been different if DSD had been used earlier?

The European Resuscitation Council states that the use of double sequential defibrillation cannot be recommended for routine use. But treating rVF is not routine and the guidelines have otherwise failed our patient. It is said that insanity is defined as doing the same thing over and over again, without changing anything, and expecting a different result. Is this not what the guidelines preach in rVF? It is up to you, the clinician, to determine whether DSD is appropriate for each rVF case you encounter. But I urge you to consider the patient in front of you and tailor your resuscitation to their needs, whether that includes DSD or an alternative option. Personally, I believe DSD does have a place in the management of rVF patients, after considering the other interventions previously discussed. Given that shock success declines over time, DSD could be used as early as the sixth shock, because at this point the guidelines have nothing further to add. Or maybe it’s me who’s insane…

James Yates (Critical Care Paramedic GWAAC)


Double sequential Defibrillation therapy for out-of-hospital cardiac arrests: the London experience. Emmerson AC, et al. Resuscitation. 2017 

A Case Series of Double Sequence Defibrillation. Merlin MA. Prehosp Emerg Care. 2016

Double sequential external shocks for refractory ventricular fibrillation. Hoch DH. J Am Coll Cardiol. 1994

Double Sequential External Defibrillation in Out-of-Hospital Refractory Ventricular Fibrillation: A Reportof Ten Cases. Cabañas JG. Prehosp Emerg Care. 2015

Double Sequential Defibrillation for Refractory Ventricular Fibrillation: A Case Report. Lybeck AM. Prehosp Emerg Care. 2015

Double simultaneous defibrillators for refractory ventricular fibrillation. Leacock BW. J Emerg Med. 2014

Simultaneous use of two defibrillators for the conversion of refractory ventricular fibrillation. Gerstein NS. J Cardiothorac Vasc Anesth. 2015

Use of double sequential external defibrillation for refractory ventricular fibrillation during out-of-hospital cardiac arrest. Cortez E. Resuscitation. 2016 

Double Sequential External Defibrillation and Survival from Out-of-Hospital Cardiac Arrest: A CaseReport. Johnston M. Prehosp Emerg Care. 2016

Dual defibrillation in out-of-hospital cardiac arrest: A retrospectivecohort analysis. Ross EM. Resuscitation. 2016

Refractory Ventricular Fibrillation Successfully Cardioverted With Dual Sequential Defibrillation. Sena RC. J Emerg Med. 2016

Dual sequential defibrillation: Does one plus one equal two? Deakin CD. Resuscitation. 2016

Magnesium therapy for refractory ventricular fibrillation. Baraka A. J Cardiothorac Vasc Anesth. 2000 



    I personally never attempt it before..but it could be the option available when managing rVF..beyond ACLS!!

  • Vanessa says:

    Your use (and indeed everyone else’s) of the word ‘asynchronous’ when describing compressions and ventilations during ALS with a ET tube in place…that word means ‘not occurring at the same time’. Do you mean to use that word as the ventilating is once every 6 seconds and the compressions are 100-120/min, so at different rates? As the main point of saying it surely is that we can now do compressions whilst we ventilate. Don’t want to be pedantic but in medicine we can get quickly drawn into using the wrong phrase, particularly if more qualified personnel use them.

    Loved the podcast though, as per usual!

    • Simon Laing says:

      Thanks for the comment Vanessa, apologies for the inappropriate use of asynchronous, you are of course right. Cheers

  • Max Feige says:

    Hello James,
    I was wondering which devices you use and if there are any concerns regarding warranty and device malfunction.
    Best regards from Germany,


    • James says:

      Hi Max,
      Apologies for the delay in replying. I use the Zoll X-Series but other providers in the area use other devices such as Lifepack 15 or Lifepack 1000. As such, all the DSD cases I’ve been involved with have used two different types of machine. With regard to malfunction/damage I am aware that it has been put forward as a possibility but I don’t think it has been investigated. I can only comment on my experience and that is, no defibrillator has failed during a resuscitation when using I’ve used DSD and, as far as I can tell, the defibrillator is still working fine after using it for DSD on several occasions.
      Have you used DSD in your practice? Any problems?
      Thanks for the comment.


      • Gareth says:

        Hi James, there is a documented case of defib failure following an overload of the motherboard following DSD, I think it was published in RESUSCITATION if I remember correctly, the manufacturer stated that the machine was not intended or insured for this “off label” usage

  • Clare Bosanko says:

    Catching up on podcasts today driving to Brum and back! This was a great summary of what little evidence there is for DSD, and the importance of optimising everything you can before considering it. We have recently been looking at introducing into our practice and wanted to develop a SOP in order to sim and make sure whole team on the same page etc. Got some advice from the ambulance service and Resus UK, as part of the process, and were strongly advised against as the manufacturers stated it could damage the machine.

    • James says:

      Hi Clare,
      Thanks for your comments and really interested to hear that you were looking to take DSD forwards as a formalised SOP. With regard to damage to defibrillators, I had read that this had been theorised as a possibility and that the manufacturers consider DSD an “off license” use. However, I couldn’t find any trials that had investigated this? Given the paucity of evidence surrounding DSD anyway, is this just another area lacking in evidence to add to the pile?

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