Abstract 20568: AMSA Combined With Prior Shock Outcome Predicts Defibrillation Success During CPR

Introduction: Amplitude spectrum area (AMSA) predicts defibrillation shock success. However, AMSA and other waveform measures require CPR interruption prior to shock, which can adversely influence survival. Hence, we evaluated whether AMSA retains its prognostic characteristics during CPR and whether electrical response to the previous shock improves prediction of shock response when combined with AMSA. We hypothesized that during CPR, combining AMSA with prior shock outcome would improve shock-specific prediction of return of organized rhythm compared to AMSA alone. Methods: Ventricular fibrillation ECG segments were collected during CPR from a convenience sample of patients who suffered an out-of-hospital cardiac arrest in a US metropolitan EMS system. The presence of CPR was identified using the chest impedance signal. Five-second ECG clips were extracted during CPR prior to the second, third, and fourth shocks. Shock success was defined as at least 2 QRS complexes within 5 seconds during the two minutes following a defibrillation attempt. ECG clips were divided randomly into training and test sets. We trained a logistic regression model to predict shock success during CPR using log AMSA combined with prior shock success. The logistic model was then compared to AMSA alone. We compared the area under the receiver operating characteristic curve (AUC) for the logistic model against that of AMSA alone using DeLong’s test for correlated receiver operating characteristic curves. Results: From 668 patients, there were 610 clips (44%) from shock 2, 460 clips (33%) from shock 3, and 305 clips (22%) from shock 4. There were 687 and 688 clips in the training and test sets, respectively. On the test set, the AUC for the logistic model combining AMSA with prior shock success was 0.74 [0.70, 0.78], and the AUC for AMSA alone was 0.66 [0.62, 0.71]. The increase in AUC for the logistic model over AMSA alone was 0.08 (p Conclusion: AMSA during CPR demonstrates some prognostic ability to predict return of organized rhythm. However, the addition of response to prior shock improves prediction during CPR. Future investigation should evaluate how waveform measures can better predict outcome while minimizing CPR interruption.