Normal Values for Time-Domain, Frequency-Domain, and Spectral Turbulence Analyses of Signal-Averaged Electrocardiograms in Healthy Subjects

Abstract

Background: Signal-averaged electrocardiograms (SAE) have mainly been studied in high risk patients with ischemic heart disease. A systemic study of the normal values and the comparative results using analytical methods has not been reported. Methods: We recorded SAE results in 200 apparently healthy subjects (100 males and 100 females, average age 28.9 years). The obtained signals were analyzed by for the time-domain (TD), frequencydomain (fast Fourier transform [FFT]), and spectral turbulence (ST) analyses. The normal values for these parameters, including differences according to gender, were evaluated. The correlation between body characteristics and individual measurements was also evaluated for each analytical method. Results were compared using previously reported criteria and gender-specific criteria. Results: The normal values for TD and FFT analyses, but not ST analysis, showed differences related to gender. A significant correlation was observed between the body characteristics noted in the TD and the FFT analyses, but this correlation was not seen for all parameters in the ST analysis. According to the conventional criteria, the rate of positive diagnosis was 9% for TD analysis, 4.5% for FFT analysis, and 2% for ST analysis. When gender-specific criteria were applied, it was 1% for TD analysis, 3.5% for FFT analysis, and 0.5% for ST analysis. However, the positive results for subjects that were found using TD analysis were discordant with the results found using FFT and ST analyses in those subjects. Conclusions: The normal values for TD and FFT analyses showed gender-related differences that were not seen using ST analysis. Gender-specific criteria are recommended when using TD analysis because it decreased positive results for healthy subjects. However, as discordant results were obtained among the various analyses, the selection of the method for analyzing the SAE and interpretation of the results should be performed with caution.