Abstract 309: High Incidences of Postshock Asystole in VF with Low AMSA Values
Purpose: Early defibrillation is critical to survival from cardiac arrest. However, defibrillation is often followed by asystole or pulseless electrical activity (PEA) in the pre-hospital setting. These non-perfusing post-shock rhythms have been demonstrated to have a worse prognosis than primary asystole or PEA. In the present study, we used registry data of out-of-hospital cardiac arrests (OHCA) to investigate the relationship between pre-shock amplitude spectrum area (AMSA) value and incidence of post-shock asystole.
Materials and Methods: A total of 543 patients treated by emergency providers following OHCA with VF as presenting rhythm were included in this study. All defibrillation shocks were attempted with ZOLL automated external defibrillators that employ rectilinear biphasic waveform. The sampling rate of the ECG was 250 Hz and only the initial shocks (120J) were analyzed. AMSA were calculated from a waveform episode of 2.05 seconds ending at 0.5 seconds before each shock attempt. Post-shock rhythms were annotated as VF, asystole/PEA and tROSC. tROSC was defined as an organized rhythm that was present for a minimum of 30 seconds, started within 60 seconds after the shock, and had a rate of 40 beats per minute or greater.
Results: The post-shock rhythms and associated AMSA readings are displayed in the Figure. The occurrence of post-shock asystole was exponentially decreased as AMSA value increased. Among those cases with AMSA<3 mvHz (N=28) defibrillation resulted in 77.8% post-shock asystole and 22.2% other non-perfusing rhythms without any cases of tROSC.
Conclusions: In this patient population, for VF with very low AMSA (<3 mvHz), asystole was the predominant post-shock rhythm and no perfusing rhythm could be restored by defibrillation alone. These patients may not benefit from early defibrillation but may require additional CPR to create myocardial perfusion. AMSA may be useful to quantify fine VF to avoid futile shocks and to continue CPR instead.
Author Disclosures: Y. Li: None. B. Chen: None. M. He: None. W. Quan: Employment; Significant; Employee of ZOLL Medical Corporation. U. Herken: Employment; Significant; Employee of ZOLL Medical Corporation.
- © 2014 by American Heart Association, Inc.