GE B20 User Manual page 82

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About the ST segment measurement algorithm
The ST segment begins at the point where the QRS ends (J point).
Diagnostic criteria of ST segment changes are measured at 60 ms
after the J point. For monitoring purposes it is important to keep the
measurement point fixed during monitoring to notice the ST
changes on the respective trends.
The sophisticated algorithms of monitor search the J and isoelectric
(ISO) points. The system learns the ECG and stores the reference
QRST complex. The algorithm sets the ISO and J points. Due to the
large variation with QRST complexes the user has possibility to
adjust the ST measurement points manually. The QRS analysis
classifies each beat by using several criteria and rejects distorted
complexes from the ST calculation.
NOTE: The ST algorithm has been tested for accuracy of the ST
segment data. The significance of the ST segment changes needs to
be determined by a physician.