Welch Allyn 1500 Patient Monitor v.1.4.X - User Manual - Manual (Page 56)

52 Monitoring and Measurements Welch Allyn 1500 Patient Monitor
ST measurement (option)
The ST segment represents the period from the end of ventricular depolarization to the
beginning of ventricular repolarization. The ST segment lies between the end of the QRS
complex and the initial deflection of the T-wave. It is normally isoelectric.
ST Analysis is a useful diagnostic tool because it may provide an early indication of
myocardial ischemia or infarction.
ST Analysis is an algorithm that analyzes the offset of the ST segment from the ECG
signal of normal beats. The offset of a reference beat is measured in millivolts (mV) (or
millimeters) with respect to the isoelectric level of the ECG waveform; the offset of
subsequent beats is measured relative to the reference beat.
The reference beat is originally obtained by learning the patient’s normal morphology, but
it can be modified by the clinician at any time using the re-learn option in the ST Analysis
Setup Window (see next page). When re-learn is selected reference beat is updated to
the current morphology.
The ST measurement is made at a point 60 or 80 milliseconds (ms) after the J-point (see
next page).
The J-point is the point on the ST segment where the slope changes (marking the end of
the QRS and the beginning of the ST segment.
Note ST re-learn is also initiated by arrhythmia re-learn.