The Effect Of Cutoff Frequency Range On Amplitude Spectrum Area Performance In Predicting Defibrillation Outcome

Introduction: Both clinical and experimental studies have demonstrated that ventricular fibrillation (VF) waveform-based amplitude spectrum area (AMSA) predicts defibrillation outcome with high sensitivity and specificity. A commonly used cutoff frequency range for calculation of AMSA is 4-48 Hz, but the median VF frequency in patients is less than 7 Hz. In the present study, we investigated whether the AMSA performance in predicting defibrillation outcome may be affected by different cutoff frequency ranges. Hypothesis: A selected cutoff frequency range would affect AMSA performance in predicting defibrillation outcome in patients. Methods: A total of 450 segments (179-defibrillation success and 271-defibrillation failure) of VF waveforms from patients with out-of-hospital cardiac arrest were analyzed. Each 4.096-s segment prior to defibrillation was acquired with a sampling rate of 250 Hz. Using MATLAB (MathWorks, Natck, MA), the AMSA of each segment of VF waveform was calculated with five cutoff frequency ranges (Shown in Figure 1). Sensitivity and specificity were calculated when defibrillation success rate was 50% which was estimated by a logistic regression curve. Area under the receiver operating characteristic curve (AUC) was used to evaluate AMSA performance within different cutoff frequency ranges. Results: AMSA threshold was decreased from 20.5 to 6.5 mV·Hz when the cutoff frequency range was changed from 3-48 Hz to 3-10 Hz (Figure 1). Sensitivity of AMSA in 3-10 Hz was increased by 81.3% compared with that of AMSA in 3-48 Hz. Specificity of AMSA in 3-10 Hz was decreased by 8.1% compared with that of AMSA in 3-48 Hz. The corresponding AUC was increased from 0.724 (3-48 Hz) to 0.768 (3-10 Hz). Conclusions: A cutoff frequency range of 3-10 Hz significantly increases the sensitivity of AMSA for predicting defibrillation success in patients with cardiac arrest with a slight decrease in specificity.