The digital filtering process in the external recording of the His bundle activity

The usual methods of recording the His bundle activity have been based on triggered signal averaging and commonly used analog filters. These filters are of low-frequency cutoff ranging from 10 to 80 Hz and high-frequency cutoff up to 300 Hz. The use of digital filters is studied in the external recording of the His bundle potential which also employs a cross-correlation function for the alignment of the waveforms. By using a low cutoff frequency of 30 Hz and a high-frequency cutoff of 250 Hz, the His bundle is found on the isoelectric line with amplitude between 4 to 7 μV. Fourier analysis of the His bundle waveform thus obtained shows that 90% of the power spectrum is below 150 Hz.