6 ECG, Arrhythmia, ST and QT Monitoring
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Choosing an ECG Lead for Arrhythmia Monitoring
It is important to select a suitable lead for arrhythmia monitoring.
Guidelines for non-paced patients are:
– QRS complex should be tall and narrow (recommended amplitude > 0.5 mV)
– R-Wave should be above or below the baseline (but not bi-phasic)
– T-wave should be smaller than 1/3 R-wave height
– the P-wave should be smaller than 1/5 R-wave height.
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 re-polarization.
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.
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.
An
** End AFIB alarm will occur when no atrial fibrillation waveform was detected for a configured
delay time.
Since most atrial flutters have regular RR 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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