ST Analysis (Optional) ECG Monitoring
4 - 30 0070- 0-0704-02 Passport V Operating Instructions
4.9 ST Analysis (Optional)
NOTE: ST analysis is available for Adult and Pediatric patients only.
FIGURE 4-27 ST Monitoring
The formula for calculating ST segment offset value is: ST segment offset value = VST-VISO. If
3-lead is detected, analysis provides one ST value from one ECG waveform (ECG1). If 5-lead
is detected, analysis provides all seven ST values.
The depression or elevation of the ST segment is measured as the vertical distance between
the isoelectric (ISO) point which provides the baseline, and the ST point (See figure above).
ST measurements are available on a maximum of three user selected ECG leads at a point
situated 80 ms (heart rate 120 bpm or less) or 60 ms (heart rate more than 120 bpm) from
the algorithmically determined end point of the QRS (J Point). In addition, the user can also
select from three (3) different settings for the ST measurement point (80, 60, or 40 ms) from
the J-point and independent of heart rate. These measurements are valid only on normal
beats. Abnormal beats, like ventricular beats, are excluded from the analysis of the ST
segment. Ventricular paced beats are also rejected from the analysis of the ST segment,
because pacemaker tails distort the shape of the ST segment.
ST segment changes are continuously measured by the monitor, but update of the displayed
ST data is different depending on the ECG cable in use. When using a 3 or 5-lead ECG
cable, the displayed ST data is updated approximately every 10 seconds.
NOTE: The ST algorithm has been tested for accuracy of the ST
segment data. The significance of the ST segment changes
must be determined by a clinician.
ST Point
J Point
ISO Point
40 to 80 msec
P
R
Q
S
T
ST deviation
(Depression or Elevation)
0
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