Beat DetectorΒΆ

In order to calculate each measure of interest (i.e. CO, TPR), MEAP applies a modified Pan-Tomkins algoritm to detect each R-peak, or heartbeat, on the ECG wave. This algoritm takes the signal (filtered per the specifications below) and squares it to amplify peaks. The resulting waveform is then smoothed with a window (see below) to further reduce noise. MEAP then detects each peak in the resulting waveform that falls above a certain threshold and marks these as R-peaks.

beat detector

The beat detector GUI allows you to:

  1. Edit the parameters of a modified Pan Tomkins QRS detector
  2. Manually add R-peaks
  3. Manually remove R-peaks

The Pan-Tompkins Method

The parameters listed under P/T processing options (the box in the bottom left corner) refer to the filters applied in the Pan-Tomkins beat detector and are as follows:

Apply Filter - unchecking this box will turn off the bandpass filters defined below.

Bandpass filters - These are intended to reduce the influence of noise due to muscle activity, electrical interference, as well as the misidentification of T-waves as R-peaks. This filter selectively reduces the signal where it falls outside the specified range. Values are, therefore, set to the range within which R-peaks are expected to occur. The defaults for the maximum and minimum are set at 5 and 15, respectively, but should be adjusted by the researcher if R-peaks are not correctly detected with these values.

For Example: if a high peak was missed, the maximum should be adjusted upwards. If secondary peaks (T-waves) were falsely marked as R-peaks, then the minimum value should be adjusted upward.

Smoothing window len - Specifies the length of the window on which the moving average function that is applied to smooth each waveform. This is done to optimize the data for a Fast Fourier Transform (FFT) which converts the signal from the time domain into the frequency domain. The default is set at 100.

Smoothing window - Specifies the shape of the smoothing function. The default Hanning Window should be used in the majority of cases.

Pt adjust - Sets the threshold above which R-peaks are detected. This setting can be adjusted from its default value of 0.001 to optimize peak detection. Lower values increase sensitivity and should be used when peaks are missed using the defaults.