JORGENSEN J1010, Руководство пользователя

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So you are a veterinary technician and you would like to
learn how to interpret electrocardiograms (ECGs). Great idea!
What is reasonable to expect of yourself? Even veterinarians
can be somewhat daunted by all those squiggly lines.
After 20 years as a technician in the cardiology section of the
Veterinary College at the University of Minnesota, I can testify
that learning to read ECGs is fun, well within your grasp, and
can be a tremendously satisfying skill to have tucked under
your belt.
You can master the technique of recording an ECG as well as
learning the fundamentals of arrhythmia interpretation.
Although, measuring the ECG to assess heart chamber enlarge-
ment is certainly not beyond your skill level, it can be a tedious
phase of the learning process. The good news is that your vet-
erinarian can use other tools, such as radiographs and ultra-
sound to determine heart chamber size. This allows us to focus
on arrythmias which are more fun and require almost no meas-
uring.
Recording the ECG
The ECG can be recorded with the patient right side down or
in a standing position with any standard ECG strip chart
recorder.
1. Attach the electrode clips directly to the skin (taking care to
attach the correct electrodes to the appropriate limbs) and mois-
ten with alcohol or gel to assure good contact.
2. Enter a 1 cm = 1 m V calibration signal.
3. Record lead II for about a minute at 25 mm/sec to assess
arrythmias. Increase the length of the tracing if an arrhythmia is
seen. If you are determined to measure waveforms as well,
record a brief tracing at 50 mm/second.
It’s helpful to center the tracing on the paper so that both the
top and bottom of the waveforms can be seen. Also, decrease
the sensitivity to 1/2 cm = 1 mV if the QRS complexes go off
the paper.
The Normal ECG
Next on the agenda is learning what a normal ECG looks like
- and why.
You probably already know all the anatomy you need. The
heart has four chambers: two atria and two ventricles. They are
connected by a conduction system that spreads an electrical
current that enables the heart to contract. The ECG is simply a
graphic recording of this electrical activity during the different
phases of the cardiac cycle.
Read Between the Lines
Learning to interpret electrocardiograms will prove invaluable to your patients and practice
By: Naomi L. Burtnick, MT (ASCP)
The normal sequence of electrical activation in the heart is as
follows:
1. Sinoatrial (SA) node - located in the right atrium.
2. Atrioventricular (AV) node - conduction link between the
atria and ventricles.
3. Left and right bundle branches - located in the left and right
ventricles.
The following waveforms are part of a single heart beat”
P wave - corresponds to atrial contraction
PR interval - corresponds to the time it takes for the impulse to
pass through the AV node
QRS waves - correspond to ventricular contraction
Q is the first negative deflection.
R is the first positive deflection.
S is the negative deflection that follows the S wave.
Note: Not all QRS complexes have a Q and an R and an S.
That’s OK.
T wave - represents ventricular relaxation. T waves can be posi-
tive or negative, but every QRS complex has to have one. If it
contracts it has to relax before it can contract again.
Calculating the Heart Rate
The heart rate (beats/min) can be calculated easily by count-
ing the number of beats (R-R intervals) between two sets of
marks in the margin of the ECG paper (3 seconds at 25
mm/sec) and multiplying by 20. ECG rulers are also available.
this is all the measuring that’s necessary.
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