Advertisement
Chapter 7: ST Monitoring
User Manual
7.1 GENERAL
ST segment deviation is defined as the displacement above or below the isoelectric level. The
measurement of deviation compares the isoelectric point to the ST measurement point.
The isoelectric point defines the point of zero voltage (no electrical activity) with a default
position of 80ms from R wave as 0msec in the horizontal (time) axis. The ST point occurs in the
ST segment between J-point and the T wave, at a default position of 110 ms after R wave. The
following figure illustrates a typical QRS complex.
ST Measurement Algorithm
The ST measurement for each beat complex is vertical difference between the two measurement
points, ST and ISO.
The ST analysis examines QRS complexes classified as normal beats (beat detection and
classification information provided by the arrhythmia algorithm are used to eliminate beat that
are ventricular in origin). The monitor combines the measurements and features of normal beats
into a composite (or average) QRS complex. It derives the ST segment deviation from this
average.
The ST segment algorithm documents changes in ST segment in adult patients that can be
indicative of the severity and duration of myocardial ischemia. Since many ischemic episodes are
silent or painless, continuous monitoring of ST segment changes can provide the earliest warning
of ischemic events.
7-2
Advertisement
Chapters
