ProSim™ 8
Users Manual
A-2
Artifact
An abnormal signal or structure produced by an external medium, such as a
muscle or electrical wiring. Artifacts are sometimes referred to as noise.
An ECG artifact can be caused by depolarization or contraction of the muscle
which depends on an electrical charge. These electrical charges can be detected
by an electrocardiogram. The electrical charges associated with the contractions
of the heart will be clear only if there is not interference by auxiliary signals from
other muscle movement. Electrical signals from power lines or local (in-wall)
circuitry represent another kind of artifact (also called noise) that can be picked
up by an ECG device. These sources can cause minute electric currents through
capacitive coupling or resistive contacts. On an ECG readout, such electrical
artifacts can cause a serious safety condition. Even a relatively tiny current of 60
hertz (Hz) can be fatal. Therefore, whenever line frequency in an
electrocardiogram is noted, the cause of the signal should be determined at once
Asynchronous
Signals sent to a computer at irregular intervals. Data is transmitted at irregular
intervals by preceding each character with a start bit and following it with a stop
bit. Asynchronous transmission allows a character to be sent at random after the
preceding character has been sent, without regard to any timing device.
Asystole (Cardiac Standstill)
No ECG activity whatsoever. Ventricular asystole is a critical condition
characterized by the absence of a heartbeat either in the ventricles or in the
entire heart. This condition, also referred to as cardiac standstill, is usually
accompanied by loss of consciousness, apnea, and—if not treated
immediately—death.
Atrial Fibrillation
A rapid, irregular atrial signal, coarse or fine, with no real P waves; an
irregularventricular rate. Coarse and fine atrial fibrillation occurs when the
electrical signals in the atria are chaotic, and multiple, ectopic pacemakers are
firing erratically. Some impulses may conduct through to the AV node to
stimulate the ventricles, causing a quite-irregular and often-rapid ventricular rate.
On the ECG there is an absence of P waves, with an irregular R-R interval.
Atrial-fibrillation waveforms are irregularly shaped and usually rounded. The
amplitude of the atrial signal is higher for coarse, and lower for fine, fibrillation.
Atrial Flutter
A repeating sequence of large, irregular P waves at 300 BPM; an irregular
ventricular response. Atrial flutter occurs when a single, ectopic, atrial pacemaker
that is non-SA (usually low, near the AV node) fires repeatedly and (usually)
regularly, producing large, pointed P waves at an approximate rate of 400 BPM
(between 240 BPM and 480 BPM). Not all of the atrial impulses conduct through
to the ventricles. On the ECG readout the waveform generally exhibits a “saw
tooth” appearance. This type of arrhythmia can reduce cardiac output by as
much as 25 %, due in many cases to the lack of an atrial “kick” and the
accompanying failure of the ventricles to fill completely with blood prior to
ventricle contraction.
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