Frequency Versus Time Domain Analysis of the Signal‐Averaged Electrocardiogram: Reproducibility of the Spectral Turbulence Analysis

Abstract

Reproducibility of the Spectral Turbulence Analysis. Spectral turbulence analysis (STA) of the signal-averaged electrocardiogram (ECG) is a new frequency domain method that analyzes the total high gain QRS complex and not only its terminal portion. This study examined the qualitative and quantitative short-term reproducibility of this technique (three recordings made within 25 min) in 68 subjects: 16 healthy volunteers; 22 patients with ventricular tachycardia and no evidence of heart disease; and 30 postinfarction patients with sustained ventricular tachycardia. The reproducibility of diagnosis of the STA was compared with that of the conventional time domain analysis of the signal-averaged ECG using standard criteria of abnormality. The reproducibility of numeric values of the spectral turbulence and of the time domain indices was performed by computing the ratios between standard deviation of measurements in individual subjects and standard deviations of all measurements. The reproducibility of diagnostic conclusions of the time domain analysis was slightly better than that of the STA but the differences were not significant (88%-91% of consistent time domain results vs 84% of consistent STA results). The numeric reproducibility of three STA parameters was slightly but not significantly inferior to that of the time domain indices whereas the reproducibility of the fourth STA variable, the intersegment correlation standard deviation (ISCSD), was significantly worse than that of the other indices. Of the two different ECG segments analyzed, the reproducibility of the STA variables calculated for the total QRS region was significantly better than that of the terminal low power QRS region. In conclusion, the qualitative and quantitative reproducibility of the STA is slightly but not significantly worse than that of the time domain analysis with the exception of the ISCSD, which is significantly less reproducible than all other parameters.