ST Monitoring Monitoring with the TM80 at the CMS
13 - 8 TM80 Telemetry Monitor Operator’s Manual
The ST segment of an ECG waveform (as shown in the above figure) represents the
period from the end of ventricular de-polarization, to the beginning of ventricular re-
polarization, or the end of the QRS complex (the J point) and the beginning of the T-
wave. ST Segment analysis is used to monitor the oxygen supply and the viability of the
heart muscle.
ST deviation is the vertical distance between the isoelectric (ISO) point level and signal
level at ST point.
The ISO point is located between the end of the P-wave and the onset of the QRS com-
plex. The ISO point provides the baseline for this measurement.
The ST point is a fixed distance from the J point at the end of the QRS complex. The ST
point can be configured to 40, 60, or 80 milliseconds past the J-point, independent of
the heart rate. By default, the ST point is positioned as follows:
ƾ at 80 milliseconds for heart rates less than or equal to 120 beats per minute
ƾ at 60 milliseconds for heart rates greater than 120 beats per minute
All available ECG leads are analyzed to measure deviations in the ST segment.
Selecting leads that contain the least amount of baseline flutter will improve measure-
ment accuracy, but accurate ST deviation measurement is dependent on the correct
location of the ISO and ST points.
ƾ ST segment analysis calculates ST segment elevations and depressions for
individual leads and then displays them as numerics in the ST digital area.
ƾ A positive value indicates ST segment elevation; a negative value indicates ST
segment depression.
WARNING
• The ST algorithm has been tested for accuracy of the ST segment data.
The significance of the ST segment changes need to be determined by a
clinician.
• ST deviation is often calculated at a fixed offset from the J point.
Changes in heart rate may affect ST.
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