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Time intervals calculation
The used method to measure the time intervals is based on analyzing 10-seconds of 12-leads ECG
signals.
Notch filter (50/60 Hz) is used to remove the artifacts and improve the signal quality and a linear
second order band-pass filter with the frequency band (0.8-18 Hz) is used to eliminate the AC
interferencece. In the next step, R wave is detected and the different beats are separated based on its
situation. R wave detection in Dena system was accomplished based on the well-known Pan-Tompkins
algorithm and by using the signal of leads I, II, V3. Based on QRS complex situation and detecting the
complex type, using windowing technique and calculating the signal slope, the exact situation of each
wave and their onset and offset points will be determined. This process is implemented on all leads
separately and in each step, the relevant outputs are saved. Finally, the best value for the start/end points
of P, QRS and T waves is selected based on Multi-Lead-Selection algorithm.
The general block diagram of the used method to determine the time intervals is as follow.
Start
12 Lead
ECG Signal
Calculate
Durations and
Final
Intervals
Results
P Duration
QRS Duration
PQ Interval
QT Interval
End
Block diagram of used method to calculate the time intervals in ECG signal
R-Detection
(Lead II)
R Positions
Pon / Poff
QRSon /QRSoff
Toff
Multilead
Selection
Single Lead
results for
12 Leads
Pre-Processing
Lynn Filter
T bound
P Bound
Figure 2-12
22
Beat
QRS Bound
Segmentation
Detection
QRS
Properties
QRS
Classification
QRSon
QRS Bound
QRSoff
Primary Beat
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