Processing ECG signals

ECG analysis

Many cardiovascular analysis techniques are performed on a ‘beat-to-beat’ basis. This requires accurate defining of the cardiac cycle and is most accurately done using the ECG. The R wave is normally the easiest waveform to identify on the ECG and represents early ventricular depolarisation.

  • Select the channel on which your ECG signal was recorded. Then click Run. The system will automatically identify the R-wave peaks which will be displayed at small red dots. If your data is noisy and the peaks are not identified well, you may consider filtering the ECG window before selecting Run.
  • Click OK to store the results and close the window.
  • You can then either analyse other signals or SAVE the file.

Control definitions

ControlFunction
Detection methodSelects the method to identify ECG features. Automatic (default) implements a variation of Pan Tompkins algorithm.

Manual implements a cross-correlation algorithm that requires the user to specify the time intervals that represent a ‘typical’ ECG complex.
Signal typeSpecifies the signal that is being analysed. The default is ECG signal.

In the absence of an ECG cardiac gating may be achieved using a Pulsatile waveform such as blood pressure.
Channel selectSpecifies the channel that corresponds to the ECG.
Invert signalInverts the signal
FilterActivates a zero-phase Butterworth filter.
Start of complexDefines the start of a representative ECG complex. We recommend the time point immediately preceding the P wave. Control is active only when the ECG detection method is set to Manual.
End of complexDefines the start of a representative ECG complex. We recommend the time point immediately after the T wave. Control is active only when the ECG detection method is set to Manual.
WindowDefines the window after the start of complex to search for the R-wave peak. Default is 0.35 seconds. Control is active only when the ECG detection method is set to Manual.
Filter typeThe type of filter used. Options are lowpass, highness, bandpass, and bandstop. Active only when the Filter control is set to ‘on’
OrderSpecifies the filter order and must be greater than zero. The default is 5. Active only when the Filter control is set to ‘on’.
Low pass frequency (Hz)Specifies the low cutoff frequency in Hz and must observe the Nyquist criterion. If the low cutoff frequency is less than or equal to 0 or greater than half of the value of sampling frequency the filtered signal is returned as empty. When filter type is Bandpass or Bandstop, low cutoff frequency must be less than high cutoff frequency. Active only when the Filter control is set to ‘on’.
High pass frequency (Hz)Specifies the high cutoff frequency in Hz. This parameter is ignored when filter type is Lowpass or Highpass. When filter type is Bandpass or Bandstop, high cutoff frequency must be greater than low cutoff frequency and observe the Nyquist criterion. Active only when the Filter control is set to ‘on’.

Processing blood pressure and transcranial doppler signals

BP-Doppler module is designed for rapid identification of beat-to-beat systolic, diastolic, and mean values from pulsatile waveforms.