User's Manual

ECG and Arrhythmia Monitoring 5-37
Adjusting QT Settings
For patients being monitored by the MX40, you can adjust QT settings in
the QT Setup window at the Information Center.
Turn QT analysis on by clicking in the QT Analysis On check box. QT
analysis is on when a checkmark displays in the check box. When the QT
measurement is on, a QT status message is displayed in the QT Setup
window, along with the current values for QT, QTc, dQTc and QT-HR. The
lead labels indicating the leads used to calculate the baseline and current
values also appear.
Note—Turning QT analysis off does not clear the baseline value. This
allows you to turn QT analysis off during prolonged arrhythmias, such as
bigeminy, without losing the baseline.
Limitations for QT Monitoring
Some conditions may make it difficult to achieve reliable QT monitoring.
When this occurs the CANNOT ANALYZE QT INOP message displays at
the Information Center, along with a QT STATUS message. Some
conditions that may make reliable QT monitoring difficult include:
T-Wave Detection Limitations.
Flat T-wave, atrial Fibrillation or atrial Flutter and prominent U-waves
can make QT monitoring difficult. For these cases you should select All
as the QT Lead on the QT window. The Information Center will use the
lead or leads that have a T-wave with sufficient amplitude and can be
detected. Alternatively select a single lead with a good T- wave
amplitude and no visible flutter activity and without a predominant
U-wave or P-wave.
QRS Changes
QRS changes such as widened QRS can affect QT monitoring. If a long
QTc is observed verify that is not caused by QRS widening.
Rhythm and Rate Limitations
Rhythm and rate limitations such as high heart rate (> 150 beats/min for
adults patients or > 180 beats/min for pediatric or neonatal patients),
paced rhythm and bigeminy rhythm can make reliable QT monitoring
difficult. If rhythm is sustained you may want to consider turning QT
interval monitoring off.
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