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Unformatted text preview: visible) look about the same in each
heart beat? Are there at least 3 R peaks visible? If you are satisﬁed with the trace, the patient can remove
the EKG Sensor leads from the electrodes (but don’t remove the electrodes yet) and you can move on to
the analysis portion. If not, collect a new trace until you are satisﬁed.
Next, label all of the visible peaks within one heartbeat with the letter indicator and the time at which
each peak occurs, as in the example in Fig. 3 in Sec. 2.4. This example uses the Lead I conﬁguration. Use
to ﬁnd the exact values. The examine functions lists the time and potential of
the examine function
the data point where the cursor is. Use the left and right arrow keys to move through the trace. Add the
labels by clicking Insert then Text Annotation. This places an input box somewhere on the graph. Type
in the label, then click elsewhere in the graph. You can move the location of the text label by hovering
your mouse over the text box until you see the hand icon. Click on the text box and drag it to the desired
location, then release the mouse. In the same way, move the annotation line to point directly to the peak.
Repeat this process to label the other peaks. Also label the time of each of the R peaks.
Once all the peaks are labeled, copy the graph by right clicking and selecting copy (or using Ctrl+C).
Paste the labeled graph into the worksheet.
Calculate the time difference between each of the R peaks, as in the example in Sec. 2.4. Use this
average time difference to calculate the patient’s heart rate. Does this heart rate fall within the typical
resting heart rate range? If it is slightly above the upper end of the range, remember that the patient was
standing while taking the EKG trace.
Calculate the P − R, QRS, and Q − T intervals and compare these to the typical values. Comment on
the intervals in your trace. Are they all close to the expected values? Does one deviate much farther from
the typical values than the other two?
Now we will determine the orientation of the patient’s heart "dipole". In Eqn. 4, there is a cosine term.
The θ is measured from the dipole’s axis. By changing the leads on the EKG sensor, we will be able to
estimate the orientation of the dipole.
Open a new graph in Logger Lite by clicking on
11 (or with Ctrl+N). You may want to save your Figure 6: Experimental Lead I, Lead II, and Lead III traces for a test patient who seems to have a nearlyperfectly-vertically oriented heart. The temporal offset between the peaks in the different traces arises
from clicking collect at different times relative to the patient’s heartbeat for each of the traces. If we had
three EKG sensors for each table, we could collect all three traces simultaneously, eliminating this offset.
previous plot if you have any doubts about it being completely done.
Connect the EKG sensor to the patient in the Lead I conﬁguration. The patient should stand comfortably. Click the Collect button to collect a new Lead I trace. When you have a good Lead I trace, click the Store icon
to save this trace. You will notice that the stored traces have a thinner line than
the current trace.
We will be taking three traces, so it is useful to label them in a descriptive way. Do this by clicking
Data then Data Set Options then clicking on the name of the trace you want to change. If you only have
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This document was uploaded on 02/15/2014.
- Spring '14