4: ECG Monitoring
The HeartStart XL+ uses the ST/AR Algorithm. Arrhythmia analysis provides information on your
patient's condition, including heart rate and arrhythmia alarms. The HeartStart XL+ uses the ECG lead
appearing in Wave Sector 1 for single-lead arrhythmia analysis.
During arrhythmia analysis, the monitoring function continuously:
Optimizes ECG signal quality to facilitate arrhythmia analysis. The ECG signal is continuously
filtered to remove baseline wander, muscle artifact and signal irregularities. Also, if the patient's
paced status is set to yes, pace pulses are filtered out to avoid processing them as QRS beats.
Measures signal features such as R-Wave height, width and timing.
Creates beat templates and classifies beats to aid in rhythm analysis and alarm detection.
Examines the ECG signal for ventricular arrhythmias and asystole.
NOTE: Because the ST/AR Algorithm is the HeartStart XL+'s cardiotach source and is needed to generate heart
rate and heart rate alarms, the algorithm can never be disabled. However, if desired, arrhythmia and heart
rate alarms can be turned off. See
ST/AR cardiotach and alarms, when activated, also work in AED mode for ECG monitoring.
As P-Waves are not analyzed, it is difficult and sometimes impossible for the algorithm to distinguish
between an aberrantly-conducted supraventricular beat and a ventricular beat. If the aberrant beat
resembles a ventricular beat, it is classified as a ventricular beat. You should always select a lead where the
aberrantly-conducted beats have an R-Wave that is as narrow as possible to minimize incorrect
Intermittent Bundle Branch Block
Bundle branch and other fascicular blocks create a challenge for the arrhythmia algorithm. If the QRS
complex changes considerably from the learned normal due to bundle branch block, the blocked beat
may be incorrectly identified as ventricular, and may cause false PVC alarms. You should always select a
lead where bundle branch block beats have an R-Wave that is as narrow as possible to minimize incorrect
When arrhythmia monitoring starts, a "learning" process is initiated. The goal is to learn the patient's
normal complexes and/or paced complexes (if the patient with an internal/transvenous pacemaker is in
paced rhythm). The learning process involves the first 15 valid (non-noisy) beats encountered during the
The QRS selected to represent the "normal" complex includes the beat that is the most frequently seen,
narrowest, on-time beat. For this reason, learning should not be initiated when the patient's rhythm is
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