Abstract 12769: Amplitude-Spectral Area of the Ventricular Fibrillation Waveform and Chest Compression Quality in Witnessed and Unwitnessed Out-Of-Hospital Cardiac Arrest: Can We Predict Who is Unlikely to Survive?

Abstract

Background: Previous investigations in human out of hospital cardiac arrest (OHCA) due to ventricular fibrillation (VF) have shown that the frequency-based waveform characteristic, amplitude spectral area (AMSA) predicts defibrillation success and is associated with survival to hospital discharge. We evaluated the relative strength of factors associated with hospital discharge including witnessed/unwitnessed status, chest compression (CC) quality and AMSA. We then investigated if there is a threshold value for AMSA that can identify patients who are unlikely to survive. Methods: Adult OHCA patients (age ≥18), with initial rhythm of VF from an Utstein-Style database (collected from 2 EMS systems) were analyzed. AMSA was measured from the waveform immediately prior to each shock, and averaged for each individual subject (AMSA-ave). Univariate and stepwise multivariable logistic regression, and receiver-operator-characteristic (ROC) analyses were performed. Factors analyzed: age, sex, witnessed status, time from dispatch to monitor/defibrillator application, number of shocks, mean CC rate, depth, and release velocity (RV). Results: 140 subjects were analyzed, [104 M (74%), age 62 ± 14 yrs, witnessed 65%]. Survival was 38% in witnessed and 16% in unwitnessed arrest. In univariate analyses, age (P=0.001), witnessed status (P=0.009), AMSA-ave (P<0.001), mean CC depth (P=0.025), and RV (P< 0.001) were associated with survival. Stepwise logistic regression identified AMSA-ave (P<0.001), RV (P=0.001) and age (P=0.018) as independently associated with survival. The area under the curve (ROC analysis) was 0.849. The probability of survival was < 5% in witnessed arrest for AMSA-ave < 5 mV-Hz, and in unwitnessed arrest for AMSA-ave < 15 mV-Hz. Conclusion: In OHCA with an initial rhythm of VF, AMSA-ave and CC RV are highly associated with survival. Further study is needed to evaluate whether AMSA-ave may be useful to identify patients highly unlikely to survive.