Datascope Passport - Mindray

Operation ST Segment Analysis (Optional Passport 2)
3.9 ST Segment Analysis (Optional Passport 2)
The ST segment of an ECG waveform (shown in FIGURE 3-16) 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 ST point is located 40 to 80 milliseconds beyond the J-point.
The ISO point is located between the end of the P-wave and the onset of the QRS complex.
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:
at 80 milliseconds for heart rates less than or equal to 120 beats per minute
at 60 milliseconds for higher heart rates
ST data is calculated on the averaged beat, and not on individual beats. The reliability of ST
measurements is lowered with the presence of atrial fibrillation, flutter, and erratic baseline
changes.
All available ECG leads are analyzed to measure deviations in the ST segment.
Learning
The process of learning is used to establish normal beat templates or a stable baseline for
accurate ST analysis. To establish this baseline, the system evaluates the first sixteen normal
beats based on readings from leads I, II and V.
To establish an accurate baseline, it is recommended that learning be done when the patient
is in stable condition, not moving, and has an ECG rhythm that is free of artifact. Learning
should not be initiated during a primarily ventricular rhythm or other ECG rhythm irregularity
because an ectopic beat may be established as normal.
ECG Filters
The ST segment of an ECG waveform often contains low amplitude signals with low
frequency content. To preserve low frequency signal content, the high pass filter is set to 0.05
Hz when ST analysis is turned on.
Passport 2 ® /Passport 2 LT Operating Instructions 0070-10-0649-01 3 - 37