Spectral analysis of the normal electrocardiogram in children and adults.

We performed spectral analysis of the X-lead Frank VCG from six normal adults (Group A) and eight normal children (Group B) using a Fast Fourier Transform. The Group A magnitudes were consistently and significantly lower than Group B in the 20--90 Hz region. Similarly, the -40 dB point was 75 Hz for Group A and 107 Hz for Group B. The P waves of the two groups had similar spectra, as did their T waves. When the entire cardiac cycle was analyzed, there was again a consistent and significant difference in the frequencies from 25--80 Hz. Despite the significant differences in the Group A and B spectra, the vast majority of the information contained in the ECG signal was confined to frequencies below 100 Hz. Therefore, a bandwidth of 100 Hz is probably adequate for accurate recording of the ECG signal from children, as well as from adults.