Abstract 224: Amplitude Spectrum Area Based Defibrillation Decision Greatly Improves Shock Success Rate and Accuracy During Prehospital Cardiopulmonary Resuscitation
Background. We retrospectively evaluated the capability of “amplitude spectrum area” (AMSA) to predict the likelihood that a defibrillation (DF) would restore a perfusing rhythm during CPR in human victims of out-of-hospital cardiac arrest. We hypothesized that threshold values of AMSA could be identified and would increase DF success rate and accuracy.
Methods. ECG data, including 1410 DFs, were obtained from 748 cardiac arrest patients from multiple areas in the US. A 4.1 secs ECG window ending at 0.5 sec before DF was analyzed and AMSA calculated prior to first DF and subsequent DFs delivered in cases of DF-resistant VF. Successful DF was defined as return of an organized rhythm within 60 sec. For first and subsequent DFs, AMSA threshold values were analyzed with regard to their ability to discriminate among successful and not successful DFs. Sensitivity, specificity, accuracy, and positive predictive value (DF success rate) of an AMSA based decision algorithm were calculated. The DF performance was then compared between two DF decision algorithms with and without AMSA threshold, respectively.
Results. A total of 1221 qualified DF events from 607 patients, with 578 first DF attempts and 543 subsequent ones for DF-resistant VF, were included in the analyses. For the DF decision algorithm without AMSA, the DF success rate and accuracy were 27%/27% for the first DFs, 9%/9% for the subsequent DFs, respectively. An optimized AMSA threshold was found to be 14 mV-Hz for first DFs and 12 mV-Hz for subsequent ones. Incorporation of these AMSA thresholds into a DF decision algorithm increased both DF success rate and accuracy. The first DF achieved a DF success rate of 54% and an accuracy of 75% while subsequent DF attempts achieved 42% in DF success rate and 89% in accuracy. These results translated into an increase of DF success rate and accuracy by 100% and 180% for the first DFs, and 360% and 880% for the subsequent DFs.
Conclusions. In this population, a defibrillation decision algorithm incorporating an AMSA threshold was confirmed to be capable to predict DF success with high accuracy. Different optimized AMSA thresholds can be selected for first and subsequent DF attempts to predict DF success with high accuracy may be selected in the case of first and subsequent DFs.
- © 2012 by American Heart Association, Inc.