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Intended Use; How The Qt Analysis Algorithm Works - Philips IntelliVue MX40 Instructions For Use Manual

Wearable patient monitor.
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Intended Use

The intended use of the ST/AR QT/QTc analysis is for use by the physician
in the risk assessment process indicated for pediatric and adult patients
with and without symptoms of arrhythmia. QT measurement is intended to
be used by qualified health professionals in hospital or clinical
environments. Composite QT (single or multi-lead derived) measures the
interval only and is not intended to produce any interpretation or diagnosis
of those measurements. Additional information regarding QT monitoring
can be found in the QT/QTc Interval Monitoring Application Note,
The device provides QT and QTc interval change information; the clinical
significance of the QT and QTc interval change information should be
determined by a clinician.

How the QT Analysis Algorithm Works

The Information Center measures the QT values once every minute during
startup. Subsequently, the Information Center updates the QT values every
five minutes. Normal or atrial paced beats and beats with a similar
morphology are averaged to form a representative waveform for further
processing. Normal beats followed by a premature QRS will be excluded
from the measurements to prevent the premature beat from obscuring the
end of the T-wave. If the algorithm cannot form a representative waveform,
for example because the morphology of the beats is too varied, the
Information Center generates a Cannot Analyze QT INOP when it detects
two consecutive invalid 5 minute values. This is also the case if normal
beats have been falsely labeled so that the algorithm does not have enough
valid beats to make QT measurements. No QT value is calculated if the
QT-HR is >150 bpm (Adult) or >180 bpm (Pedi/Neo).
Because of the different algorithm approaches, a QT/QTc measurement
from a diagnostic 12-lead program may differ from the realtime
For QT interval monitoring to be effective, basic or enhanced arrhythmia
monitoring must be on.
ECG and Arrhythmia Monitoring


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