Download Electrocardiography II. Determination of the cardiac axis Analyis and

Electrocardiography II.
Determination of the cardiac axis
Analyis and evaluation of the recorded data
Name of the students:
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Teacher:
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Date:
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Subject profile
Name: ...................................................
Height: ...............................
Age: ...................................................
Weight: ........................................
Gender: male / female
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Goals of the practical lesson (brief definition in a few sentences)
Introduction (can be continued on a separate sheet if needed)
1. What kind of information the Einthoven triangle can provide?
Principles of calculating the Einthoven triangle (summary of the most
important facts in regard to the analysis of the practical data)
2. Methods and materials (schematic enumeration)
3. Technical details of the practical exercises (preparation of the subject, settings of
the recording system, explanation of the exerted tasks)
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A. Data and Calculations
I. Determination of the direction of the R-wave
Mark the polarity („+” or „-” ) of the R-wave in the table below.
R-wave
Lead
+
-
Einthoven I (CH 1)
Einthoven II (CH 40)
Einthoven III (CH 3)
II. Determination of the amplitude of potential changes accompanied by
ventricular depolarization
Analyze 5 consequtive cardiac cycles and measure the amplitude of the R-wave from the baseline
in case of Einthoven I (CH 1) lead and Einthoven III (CH 3) leads, respectively. For this, use the
∆ (delta amplitude) measurement and select the area between the R peak and the baseline before
the QRS complex by the I-beam cursor. Calculate the mean value. As the ∆ (delta amplitude)
measurement computes the amplitude difference between the start- and the end point of the
selected area, polarity of the measured value will be determined by the selection order of the end
points. Attach the magnified, analyzed recording segments to the lab record and note the
number of the attachments.
1. Seated position:
amplitude (∆
∆) [..............]
1.
2.
Cardiac cycle
3.
4.
5.
mean
amplitude
[............]
Einthoven I (CH 1)
Einthoven III (CH 3)
Number of the attachment:.....................
2. Standing position:
amplitude (∆
∆) [..............]
1.
2.
Einthoven I (CH 1)
Einthoven III (CH 3)
Number of the attachment:.....................
Cardiac cycle
3.
4.
5.
mean
amplitude
[............]
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III. Determination of the direction and amplitude of the electrical cardiac
axis
Construct the electrical axis of the heart using the mean amplitude of the R waves in case of
Einthoven lead I. and III. Draw a perpendicular line from the ends of the vectors (right angles to
the axis of the lead) using a protractor or right angle guide. Determine the point of intersection of
these two perpendicular lines. Draw a new vector from point 0,0 to the point of intersection. The
direction of the resulting vector approximates the mean electrical axis of the heart, while the
length of the vector approximates the mean potential of the heart.
1. Seated position:
mean electrical axis (angle):......................˚
amplitude:.................................mV
2. Standing position:
mean electrical axis (angle):......................˚
amplitude:.................................mV
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B. Data summary and conclusions
Effect of body posture on the direction of the electrical axis of the heart
left
dev.
p a th
ol
right ogical
devia
tion
Draw the mean electrical vectors corresponding to the seated and standing position, respectively,
on the figure below. Use different colours to mark the vectors corresponding to the different body
postures.
pa
t
left holog
ica
de
l
v ia
tion
no
d
ia
ev
tio
n
right
dev.
Normal and disordered QRS main axis postions in the hexaxial reference system
Body posture
Position of the cardiac
range
axis [º]
seated
standing
a) Was there a difference in the direction of the QRS main axis in case of seated vs. standing
positions?
Yes
No
b) Explain the results.
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c) Make a list about the physiological or pathological conditions which can change the direction
of the electrical axis.
(pathological) left axis deviation:
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(pathological) right axis deviation:
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C. Definitions
ECG:……………………....................................................................................................................
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Einthoven’s rule:...……....................................................................................................................
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Einthoven’s triangle:.........................................................................................................................
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