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Resuscitation. 2019 Jul;140:194-200. doi: 10.1016/j.resuscitation.2019.04.042. Epub 2019 May 4.

An investigation of inter-shock timing and electrode placement for double-sequential defibrillation.

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Physio-Control/Stryker, 11811 Willows Rd. NE, Redmond, WA 98052, USA. Electronic address:
Cardiac Rhythm Management Laboratory, University of Alabama at Birmingham, 1670 University Blvd Volker Hall, B140, Birmingham, AL 35294-0019, USA.
Physio-Control/Stryker, 11811 Willows Rd. NE, Redmond, WA 98052, USA.



Double-Sequential Defibrillation (DSD) is the near-simultaneous use of two defibrillators to treat refractory VF. We hypothesized that (1) risk of DSD-associated defibrillator damage depends on shock vector and (2) the efficacy of DSD depends on inter-shock time.


Part 1: risk of defibrillator damage was assessed in three anaesthetized pigs by applying two sets of defibrillation electrodes in six different configurations (near-orthogonal or near-parallel vectors). Ten 360J shocks were delivered from one set of pads and peak voltage was measured across the second set. Part 2: the dependence of DSD efficacy on inter-shock time was assessed in ten anaesthetized pigs. Electrodes were applied in lateral-lateral (LL) and anterior-posterior positions. Control (LL Stacked Shocks; one vector, two shocks ∼10 s apart) and DSD therapies (Overlapping, 10 ms, 50 ms, 100 ms, 200 ms, 500 ms, 1000 ms apart) were tested in a block randomized design treating electrically-induced VF (n = ∼89 VF episodes/therapy). Shock energies were selected to achieve 25% shock success for a single LL shock.


Part 1: peak voltage delivered was 1833 ± 48 V (mean ± 95%CI). Peak voltage exposure was, on average, 10-fold higher for parallel than orthogonal vectors (p < 0.0001). Part 2: DSD efficacy compared to Stacked LL shocks was higher for Overlapping, 10 ms, and 100 ms (p < 0.05); lower at 50 ms (p < 0.05); and not different at 200 ms or longer inter-shock times.


Risk of DSD-associated defibrillator damage can be mitigated by using near-orthogonal shock vectors. DSD efficacy is highly dependent on the inter-shock time and can be better, worse, or no different than stacked shocks from a single vector.


University of Alabama at Birmingham Institutional Animal Care and Use Committee (IACUC) Protocol Number 06860.


Defibrillator damage; Double-sequential defibrillation; Refractory ventricular fibrillation

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