.
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5) Change the searching range of 30ms-100ms to 100ms-350ms in step 1, repeat step 1-4.
6) If the found P-wave is still narrow, it means that P-wave doesn’t exist.
4. Find T-wave
1) Peak of T-wave: search the max value within 30ms-300ms after the end of QRS-complex,
save it as the peak of T-wave.
2) Threshold value of the beginning of T-wave: search the minimal value within 0ms-100ms
after the end of QRS-complex, the minimal value plus 1/10 of the peak value of T-wave is the
threshold for finding the beginning of T-wave.
3) Threshold value of the end of T-wave: search the minimal value within 200ms after the peak
of T-wave, the minimal value plus 1/10 of the peak value of T-wave is the threshold for finding
the end of T-wave.
4) Find the beginning of T-wave: in the range between the minimal value in step2 and the peak
of T-wave, find a point that less than the threshold value of the beginning of T-wave, the point is
the beginning of T-wave.
5) Find the end of T-wave: in the range between the minimal value in step3 and the peak of
T-wave, find a point that less than the threshold value of the end of T-wave, the point is the end
of T-wave.
5. Explanation of equipotential segment
In searching the QRS-complex, this algorithm adopts the analysis method of superposition of the
slopes for all leads, therefore, the equipotential segments before and after the QRS-complex are
partly included in the start and end points of the QRS-complex. It is depends on the number of
leads containing equipotential segments. If there are more leads containing equipotential
segments, the slope value will be smaller after superposition, so it is difficult to meet the
threshold condition, and only a small part of the equipotential segments is counted to the start
and end points of the QRS-complex. On the contrary, if there are less leads containing
equipotential segments, a large part of the equipotential segments will be counted to the start and
end points of the QRS-complex. Anyway, the equipotential segments before and after the
QRS-complex are partly included in the QRS-complex duration.
3.3 Amplitude measurement
After finding the position of each wave, i.e. the start and end points of P wave, QRS
complex and T wave, use the following method to measure P, Q, R, S, ST and T waves of each
lead.
1. P-wave
Calculate the average value of the data 20ms before the start point of P wave, and use this
average value as the baseline of P wave. Find the max value between the start point and end
point of P wave, the difference between the max value and the baseline would be the amplitude
of P wave.
2. Q/R/S wave
Calculate the average value of the data 10-30ms before the start point of QRS complex, and use
this average value as the baseline of QRS complex. Search boundary points that exceeding the
baseline from the start point of Q wave to the end point of S wave. Each adjacent two boundary
