Interesting case reports on cardiac arrest patients with refractory VF. One was shocked 7 times – with a change in pad location. No luck. For the 8th shock, they hooked the patient up to a second defibrillator, and shocked him sequentially. One defib fired straight after the other in a 1-2 punch fashion. And got him into sinus rhythm.
Double Sequential Defibrillation
The standard pad shifts in single shock would be to optimise pad placement, or to try to change to anterior/posterior pads. In this set-up of Double Sequential Defibrillation (DSD) they had two pads in the standard position, and two pads in the anterior/posterior position. Then, trying to press the shock buttons of the defibrillators simultaneously, which would give you two shocks in quick succession.
Awesome slide kindly provided by @srrezaie
And there is some evidence backing up Double Sequential Defibrillation. Animal studies have shown DSD to successfully break VF when single shocks haven’t. And DSD needs a lower total amount of energy than a single shock to cardiovert these animals. There’s even a human study in 21 healthy volunteers who got induced VF in an electrophysiology lab, and randomly tested with internal, epicardial leads for single shock or DSD. Try getting that protocol past the ethics committe today!. The DSD had a much lower defib threshold, and some volunteers that didn’t convert on repeated single shocks, did so on DSD as a rescue method.
The mechanism behind it is proposed to be the change in vector, as well as these double shocks possibly shock a larger proportion of the myocardium. The shocks need to come fairly close together, so the DSD set-up with to separate defibrillators are quite different to the advanced and controlled settings in an electrophysiology lab. Still, there’s also a case series of ten patients with refractory VF after 6-11 shocks. DSD broke the VF in 7 of them. Unfortunately none of these patients survived to discharge, while the single case report made a full recovery.
An interesting concept and case reports. I’m still unsure exactly how well this works in the real world, but in selected cases of refractory VF it could be something to keep in mind when your resus is going nowhere.