User's Manual

How the QT Analysis Algorithm Works
ST/AR Arrhythmia Monitoring
7-23
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.