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User Guide
CEPAS
Figure 44. FFT with alternate FFT settings.
This shows a computed DF of 5.2Hz and Organisation Index of 0.7 which are similar but not the same as
initially calculated.
For other channels, where there is not a clear fibrillatory wave, the same procedure can be applied.
However caution must be taken when interpreting the FFT results! See for example Lead V2 shown in
Figure 45 below.
Figure 45. Lead V2 subtraction.
The subtracted signal in this case is most likely residual from the template subtraction procedure. The FFT
of this signal should not be used to infer any Dominant Frequency.
Significant energy appearing at low frequencies in the FFT may be caused by several factors. One factor is
baseline wander. The calculation of the DF in CEPAS can be set to reject very low frequencies that are not
representative of repetitive cardiac activity. In Figure 45 DF is calculated as 3.3Hz although there is a peak
at a lower frequency than this. The DF calculation is initially based on the minimum and maximum
frequency scale values as set on the graph. The scale can be adjusted directly on the graph. The frequency
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