Patient Monitor User Manual Monitoring ECG
- 109 -
- QRS should be tall and narrow (recommended amplitude> 0.5 mV)
- R wave should be above or below the baseline (but not biphasic)
- T wave should be smaller than 1/3 of the R wave height
- P wave should be smaller than 1/5 of the R wave height.
For paced patients, in addition to above guidelines, the pacemaker signal should also:
- not wider than normal QRS
- The QRS complexes should be at least twice the height of the pacing pulse
- large enough to be detected, without repolarization signal
According to Standard ISO60601-2-27, the minimum detection level of the QRS complex is set
to 0.15 mV, to prevent the detection of P-wave or baseline noise as QRS complexes. Adjusting
ECG displayed waveform size (gain adjustment) won’t influence ECG signals which are used for
arrhythmia analysis. If the ECG signal is too small, a false asystole alarm may occur.
Aberrantly-Conducted Beats:
As not recognizing the P waves, the monitoring system is difficult to distinguish between
aberrantly-conducted beats and ventricular heartbeat. If the aberrantly-conducted beat is similar
to ventricular tachycardia, it may be classified as ventricular. Make sure to select such a lead, the
aberrantly-conducted beats have an R wave that is as narrow as possible to minimize the incorrect
calls. The ventricular should have a different appearance from “normal heartbeat”. Physicians
should be more alert to these patients.
Intermittent bundle branch block: bundle branch block or other bundle obstruction phenomenon
is a challenge for arrhythmia algorithm. If the QRS wave during the block has a considerable
change in morphology compared to the normal QRS of learning, the blocked heartbeat may be
misclassified as ventricular tachycardia, resulting in an incorrect chamber alarm. Make sure to
select such a lead, which blocks the heartbeat of the R wave as narrow as possible to minimize
the wrong classification. Ventricular heartbeat should have a different appearance from “normal
heartbeat”. Physicians should be more alert to these patients.
NOTE:
1 Heart rate reading may be affected by cardiac arrhythmias. Do not rely entirely on
heart rate alarms when monitoring patients with arrhythmia. Always keep these
patients under close surveillance.
2 Since the arrhythmia detection algorithm sensitivity and specificity is less than 100%,
sometimes there may be some false arrhythmias detected and also some true
arrhythmia events may not be detected. This is especially true when the signal is
noisy.
3 The ventricular HR mentioned above refers to:
In basic ARR, when the consecutive PVCs number ≥ 5, the algorithm calculates
ventricular HR with the average of 4-8 RR intervals.
In advanced ARR, when the consecutive PVCs number ≥ 3, the algorithm
calculates ventricular HR with the average of 2-8 RR intervals.
To Next Page
Loading...
