Abstract 20547: AMSA-Based Shock Decision: a Human Retrospective Analyses During Pre-Hospital CPR Intervention
Background: Electrical defibrillation (DF) is the only intervention to terminate ventricular fibrillation (VF) cardiac arrest. Nevertheless, decision of interrupting CPR for delivering of a DF might be controversial and may lead to repetitive unnecessary DFs and ultimately to worse outcome. The goal of the present study was to retrospectively evaluate the accuracy of AMSA in predicting whether a DF would reverse VF and its use in an AMSA-based DF decision algorithm on guiding CPR interventions.
Methods: 1410 ECG data were obtained from 748 patients through an internal registry of ZOLL AED Pro and AED Plus defibrillators from multiple areas in the US. AMSA was calculated based on a 1024 point ECG window ending at 0.5 sec before each DF. DF was defined as successful in the presence of spontaneous rhythm ≥ 40bpm starting within 60 secs from the shock and lasting for > 30 secs. A range of AMSA thresholds was also evaluated.
Results: A total of 1291 quality DF events from 609 patients were included in the analyses. Before the first DF, mean AMSA was 16.8 mV-Hz when shocks were successful, while it was 11.4 (p<0.0001) in those that were not. After the first DF, AMSA significantly decreased (Table), but remained higher in successful shock episodes (15.0 vs. 7.4 mV-Hz, p<0.0001). With an AMSA threshold of 7.5 mV-Hz, a large amount of unnecessary DFs (35% for the first DF and 50% for the subsequent DFs) were avoided by using AMSA with the accuracy of 93% for the 1st DF and 95% for the subsequent DFs. Decreasing the threshold value, accuracy of AMSA in guiding the shock decision further improved (Table).
Conclusions: In this population, AMSA was confirmed to be significantly higher in the presence of successful DF. Moreover, an AMSA-based DF decision algorithm appeared as a useful approach to avoid many unnecessary and potentially harmful DFs.
- © 2010 by American Heart Association, Inc.