6 ECG, Arrhythmia, ST and QT Monitoring
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For paced patients, in addition to the above, the pace pulse should be:
– not wider than the normal QRS
– the QRS complexes should be at least twice the height of pace pulses
– large enough to be detected, with no repolarization.
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 IEC 60601-2-27 and 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 R-R irregularity, P-R
interval variability and P wave variability.
In order to generate an Afib alarm the following criteria must be detected for 1 minute:
• normal beat R-R intervals must be irregular
• P-R 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.
An
* End AFIB alarm will occur when no atrial fibrillation waveform was detected for a configured delay
time.
Since most atrial flutters have regular R-R intervals, they cannot be detected by the atrial fibrillation
algorithm.
An
* AFIB 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 and * End AFIB alarms 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.
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