5 ECG, Arrhythmia, ST and QT Monitoring
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To prevent detection of P-waves or baseline noises as QRS complexes, the minimum detection level
for QRS complexes is set at 0.15 mV, according to AAMI-EC 13 specifications. Adjusting the ECG
wave size on the monitor display (gain adjustment) does not affect the ECG signal which is used for
arrhythmia analysis. If the ECG signal is too small, you may get false alarms for pause or asystole.
Aberrantly-Conducted Beats
As P-waves are not analyzed, it is difficult and sometimes impossible for the monitor to distinguish
between an aberrantly-conducted supraventricular beat and a ventricular beat. If the aberrant beat
resembles a ventricular beat, it is classified as ventricular. You should always select a lead where the
aberrantly-conducted beats have an R-wave that is as narrow as possible to minimize incorrect calls.
Ventricular beats should look different from these 'normal beats'. Instead of trying to select two leads
with a narrow R-wave, it may be easier to just select one lead and use single lead arrhythmia
monitoring. Extra vigilance is required by the clinician for this type of patient.
Atrial Fibrillation Alarm
The monitor performs atrial fibrillation analysis using information about the RR irregularity, PR
interval variability and P wave variability.
In order to generate an Afib alarm the following criteria must be detected for 1 minute:
• normal beat RR intervals must be irregular
• PR interval deviation must be large
• P-wave region must not match well
Atrial fibrillation analysis is only available for adult patients and atrial fibrillation detection cannot be
performed on PVCs or Paced beats.
Since most atrial flutters have regular RR intervals, they cannot be detected by the atrial fibrillation
algorithm.
An Afib alarm can be falsely detected in the presence of:
• sinus arrhythmia,
• muscle noise, or
• electrode motion artifact.
If you also have monitors with earlier software revisions, the Afib alarm will not be generated after a
transfer to one of these monitors. Always leave the Irregular HR alarm switched on, so that this alarm
can be generated in such situations.
See the Application Note on Arrhythmia/ST supplied on your documentation DVD for detailed
information on the arrhythmia algorithm and ECG analysis.
Intermittent Bundle Branch Block
Bundle branch and the other fascicular blocks create a challenge for the arrhythmia algorithm. If the
QRS during the block changes considerably from the learned normal, the blocked beat may be
incorrectly classified as ventricular, causing false PVC alarms. You should always select a lead where
the bundle branch block beats have an R-wave that is as narrow as possible to minimize incorrect calls.
Ventricular beats should look different from these 'normal beats'. Instead of trying to select two leads
with a narrow R-wave, it may be easier to just select one lead and use single lead arrhythmia
monitoring. Extra vigilance is required by the clinician for this type of patient.
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