FREQUENCY VERSUS TIME-DOMAIN ANALYSIS OF THE SIGNAL-AVERAGED ELECTROCARDIOGRAM - REPRODUCIBILITY OF THE SPECTRAL TURBULENCE ANALYSIS

Reproducibility of the Spectral Turbulence Analysis. Spectral turbulen ce analysis (STA) of the signal-averaged electrocardiogram (ECG) is a new frequency domain method that analyzes the total high gain QRS comp lex and not only its terminal portion. This study examined the qualita tive and quantitative short-term reproducibility of this technique (th ree recordings made within 25 min) in 68 subjects: 16 healthy voluntee rs; 22 patients with ventricular tachycardia and no evidence of heart disease; and 30 postinfarction patients with sustained ventricular tac hycardia. The reproducibility of diagnosis of the STA was compared wit h that of the conventional time domain analysis of the signal-averaged ECG using standard criteria of abnormality. The reproducibility of nu meric values of the spectral turbulence and of the time domain indices was performed by computing the ratios between standard deviation of m easurements in individual subjects and standard deviations of all meas urements. The reproducibility of diagnostic conclusions of the time do main analysis was slightly better than that of the STA but the differe nces were not significant (88%-91% of consistent time domain results v s 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), wa s significantly worse than that of the other indices. Of the two diffe rent ECG segments analyzed, the reproducibility of the STA variables c alculated for the total QRS region was significantly better than that of the terminal low power QRS region. In conclusion, the qualitative a nd quantitative reproducibility of the STA is slightly but not signifi cantly worse than that of the time domain analysis with the exception of the ISCSD, which is significantly less reproducible than all other parameters.