S12 Vet Monitor User’s Manual
8-24
3. Select 【ST Point】 to set the position of ST Point.
The setting of 【Auto Adjust】 defines the method of adjusting the ISO point and J
point. When the 【Auto Adjust】 switch is turned on, the module automatically adjusts
the positions of ISO and J points according to the current waveform. When the 【Auto
Adjust】 switch is off, you can manually adjust the positions of 【ISO】 and 【J】
through “+” and “-”.
The ISO point (isoelectric) position is given relative to the R-wave peak.
Position the ISO point in the middle of the flattest part of the baseline
(between the P and Q waves).
The J point position is given relative to the R-wave peak and helps locating
the ST point. Position the J point at the end of the QRS complex and the
beginning of the ST segment.
The ST point is located at a fixed distance relative to the J point, and the J
point is moved so that the ST point is located in the middle of the ST segment.
The ST point can be located at the positions of J+0, J+20, J+40, J+60, and
J+80.
8.8. QT/QTc Monitoring
QT interval is the time from the beginning of QRS complex to the end of T wave, that
is, the whole period of ventricular action potential depolarization (QRS interval) and
repolarization phase (ST-T). QT test can help you to judge long QT interval syndrome.
QT interval is negatively correlated with heart rate. As heart rate increases, the QT
interval shortens, while at lower heart rates QT interval gets longer. We can use several
formulas to correct QT interval according to heart rate. The QT interval corrected by heart
rate is called QTc.
8.8.1. QT/QTc measurement limitation
The following conditions may affect the accuracy of QT measurement:
The amplitude of R wave is too low.
Excessive ventricular heartbeat.
RR interval is unstable.
High heart rate causes P wave to invade the end of the previous T wave.
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