Philips IntelliVue TRx, Instructions For Use Manual

Page: 143 / 274

Draft - 1 Aug 08
ST/AR QT Interval Algorithm
ST/AR Arrhythmia Monitoring 7-15
What is QT
Interval
Monitoring
Of special concern for QT monitoring is the administration of QT prolonging
drugs to patients identified with risk factors for Torsade de Pointe. Females,
older patients and patients with bradycardia, impaired left ventricular function
(ischemia, left ventricular hypertrophy), hypokalemia and hypomagnesemia are
in this increased risk category.
QT interval monitoring can assist in the detection of prolonged QT interval
syndrome.The QT interval in an ECG lead is the time interval from the onset of
the earliest deflection in the QRS complex to the end of the T wave. For
patients being monitored by an IntelliVue Telemetry System device, the
Information Center measures the QT values once every minute during startup,
during the learning phase and on lead mode change. After that the Information
Center updates the QT values every five minutes.
The QT interval has an inverse relationship to heart rate. Faster heart rates
shorten the QT interval and slower heart rates prolong the QT interval. To
correct the QT interval for heart rate the Information Center uses the Bazett
correction formula by default. Your system, however, may be set up to use the
Fridericia correction formula as an alternative. The heart rate corrected QT
interval is abbreviated as QTc.
R
P
Q
S
T
QT Interval