Operator's Manual

QT/QTc Interval Monitoring Monitoring ECG
7 - 22 TM80/TM70 Telemetry Monitor Operator’s Manual
QT/QTc interval monitoring is intended for adult and pediatric patients.
7.8.1 QT/QTc Monitoring Limitations
Some conditions may make it difficult to achieve reliable QT/QTc monitoring, for
example:
■ R-wave amplitudes are too low
■ The presence of frequent ventricular ectopic beats
■ Unstable RR intervals
■ P-waves tending to encroach on the end of the previous T-wave at high heart rates
■ The T-wave is very flat or T-wave are not well defined
■ The end of the T-wave is difficult to delineate because of the presence of U-waves
■ QTc measurements are not stable
■ In the presence of noise, asystole, ventricular fibrillation, atrial fibrillation, and ECG
lead off
For these cases you should select a lead with good T-wave amplitude and no visible
flutter activity, and without a predominant U-wave or P-wave.
Some conditions such as left or right bundle branch block or hypertrophy can lead to a
widened QRS complex. If a long QTc is observed you should verify it to ensure that it is
not caused by QRS widening.
Because normal beats followed by ventricular beats are not included in the analysis, no
QT measurement will be generated in the presence of a bigeminy rhythm.
If the heart rate is extremely high (over 150bpm for adults and over 180bpm for
pediatrics and neonates), QT will not be measured. When the heart rate changes, it can
take several minutes for the QT interval to stabilize. For reliable QTc calculation it is
important to avoid measurements when the heart rate is changing.
7.8.2 Enabling QT/QTc Monitoring
The QT monitoring function is disabled by default. Before you start QT monitoring,
enable the QT function. To do so, follow this procedure:
1. On the main screen, tap the HR digital area or ECG waveform area to enter the
[ECG] menu.
2. In the [ECGParameter Setup] section, tap [QT/QTc].
3. Switch on [QT Analysis].