Abstract 97: Dual Pathway Defibrillator Shocks Produce Less Hemodynamic Compromise than Standard, Single Pathway Shocks
Emergency ventricular defibrillation is conventionally performed using a single pair of external electrodes. We have shown that the use of two defibrillators, discharged simultaneously, or sequentially (dual pathway; DP), during ventricular defibrillation can convert the heart to sinus rhythm with significantly lower total energy using similar waveforms compared to single pathway (SP) shocks. Studies have also shown that high energy SP biphasic waveform shocks can produce immediate, post-shock hypotension, although less than monophasic shocks. This study was designed to determine if high energy DP shocks produce a similar hemodynamic effect as SP biphasic shocks at the same energy.
Methods: Defibrillator testing was performed using eight pigs of either sex (range 32– 41 kg). Animals were anesthetized with isoflurane and instrumented with surface ECG to monitor rhythm and arterial cannula to monitor systemic blood pressure. Self adhesive defibrillation electrodes (Zoll Medical) were placed on the shaved torso in an anterior-posterior orientation in both SP and DP configurations. High energy defibrillator shocks (total energy 200J for RLB and BTE waveforms) were delivered in sinus rhythm to compare a DP rectilinear biphasic waveform (DP-RLB: Zoll Medical) to a SP-RLB waveform and an SP biphasic truncated exponential (BTE: Physio-Control) waveform. The immediate post shock reduction in mean arterial blood pressure (as percent of pre-shock value) were recorded and compared. The 200J shock strength was chosen due to it’s high shock efficacy in this population (approximately 3 times defibrillation threshold).
Results: The DP-RLB waveform configuration produced a post-shock reduction of 5.4 ± 9.6% in mean arterial pressure, while the SP-RLB waveform reduction was 14.1± 8.4% and the SP-BTE waveform reduction was 13.0 ± 6.0% at the same 200J total energy (p<0.03) .
Conclusions: The DP shock configuration using the RLB waveform produces less reduction in mean arterial pressure following high energy shocks than both the RLB and the BTE waveforms using a single pathway configuration. Further studies would need to be performed to determine if this hemodynamic benefit would be greater following a period of ventricular fibrillation, as would be seen clinically.