Double sequential external defibrillation (DSED) can be used in ventricular fibrillation (VF) which remains refractory to conventional ACLS protocols. It involves utilizing two defibrillators to rapidly deliver two shocks in succession to increase energy sent to the myocardium with multiple vectors at a lower shock impedance. This technique has also been used to cardiovert patients with atrial fibrillation as shown in this image.
Two pairs of defibrillator pads are placed: one in the anterior-lateral position and the other typically in the anterior-posterior position. The defibrillators are charged to the recommended or maximum energy level. Then, the shocks are typically delivered by one individual pushing both buttons simultaneously to minimize the delay.
The evidence supporting DSD is mixed, primarily from case reports and small case series. Some of these reports suggest an improvement in rhythm conversion rates, while others highlight the need for more rigorous research to understand the effectiveness and safety of this intervention.
The International Liaison Committee on Resuscitation (ILCOR) now recommends DSED in patients with VF refractory to three conventional attempts at defibrillation. The data supporting this stems from a single randomized controlled trial that showed higher survival and improved neurological outcomes in patients with refractory VF who received DSED instead of additional conventional defibrillation. The successful implementation of this guideline change will depend on having the equipment available, appropriate training of personnel, and differentiating refractory VF from recurrent VF.
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