Skip to main content

DOSE VF - Vector Change vs DSED

Question# 728

My question is about dual sequential defibrillation.

My service was part of dose vf study which I received training on. I noticed in one of the medic news posts they mentioned paramedics who received this training are able to continue to perform VC and DSED on patients in refractory vf and vt. I’d just like to clarify if this is something we can do independent of BHP consultation or if calling a BH is still preferred? And if so is it recommended to go straight from A/L pads to DSED vs VC? Is it best to do 3 initial shocks before changing or is it appropriate to do so sooner?


When patients are in a refractory (persistent after 3 consecutive shocks) VF or pVT rhythm, the RPPEO would recommend considering either a change in the pad placement, or the use of double sequential external defibrillation. Either treatment can be applied by PCPs or ACPs.

By switching pad positioning from the standard anterior-lateral position to anterior-posterior position, the voltage gradient across the left ventricle (a posterior structure composing the largest myocardial component of the heart) is greater. The DOSE VF study that you refer to, demonstrated improved survival when changes in pad positioning were performed after VF/pVT was determined to be refractory to the initial three shocks (21.7% vs 13.3%).

Paramedics in the RPPEO can implement vector change in their practice immediately when faced with a patient in refractory VF/pVT – a patch to a BHP is not necessary.

When it comes to Double Sequential External Defibrillation (DSED), this is where it gets a little complicated. Though it is currently being discussed at the MAC, there is currently no medical directive in place, and the AHA guidelines have not yet caught up to these promising results. We are hopeful these changes will be reflected shortly in upcoming iterations of the ALS PCS, and can be rolled out in future CMEs.

Having said that, the Medical team, and patch physicians are comfortable with paramedics patching to apply DSED, provided that they have been trained to the skill.

Given the even greater improvement in survival with DSED (30.4% vs 13.3%), we would encourage its use over vector change, but we understand the logistical challenges of a) ensuring a second defibrillator is on scene; b) requiring a patch point; and c) ensuring the paramedic(s) is trained in the safe use of DSED. Further, we recommend this only be applied after 3 unsuccessful shocks.

In the meantime, if you’d like to learn more about the study, Education Coordinator Zach Cantor had Dr. Cheskes on his podcast, Critical Levels, to discuss the study. It’s available for elective CME on MedicLEARN (

Thank you for advocating for your patients and the community by considering the most up-to-date literature!


- RPPEO July MedicNEWS
- Sheldon Cheskes et al., 2022. Defibrillation Strategies for Refractory Ventricular Fibrillation. New England Journal of Medicine, Volume 387, pp. 1947-1956. DOI: 10.1056/NEJMoa2207304.


30 August 2023

ALSPCS Version




Please reference the MOST RECENT ALS PCS for updates and changes to these directives.