The document provides information about recording and interpreting an electrocardiogram (ECG). It describes how the ECG works by recording the heart's electrical activity. It outlines the 18 step procedure for performing an ECG exam, including preparing the patient, attaching electrodes, taking a recording, and analyzing segments and intervals. Key aspects like measuring heart rate using a 15 second recording at 50:1 compression are also covered. The document aims to prepare students for the ECG station of an OSCE exam.

1. Recording & interpreting the ECG

2. Contents
• What is the ECG?
• How does it work?
• Procedure for the OSCE
• Tips for this station
• Questions

3. What is the ECG?
• ECG stands for electrocardiogram
• Its a recording of the heart’s electrical activity
• Useful in demonstrating heart pathology
1
Voltage 0.5
(mV)
0
-0.5
Time (msec)

4. How does it work?

5. How does it work?

Time

6. The procedure
1. Relax, but be ready
2. Wash your hands using the gel provided
3. Introduction, explanation, consent
“Good afternoon. My name is Umar Hussain and I’m a 1st year
medical student. I’m here today to record an ECG exam.
Basically it will involve me attaching these wires on to your
wrists and ankles; the computer will take a recording for
about a minute and then we’d be done. At no point should this
exam be painful, but if it does get to that stage then please let me
know. Is this ok with you?”

7. The procedure
4. The patient will already have electrodes
attached to them but if not:
– Clean the inside of both wrists and ankles with a
mediswab
– Attach 5 electrodes to the patient:
• 2 for the right wrist
• 1 for the left wrist
• 1 for the left ankle
• 1 for right ankle

8. The procedure
5. Connect the wires in the following sequence:
– Right wrist: Red and white
– Left wrist:
– Right ankle: Green
– Left ankle:
The wires should have labels on them (e.g. RA for right
arm on the red and white wires) but learn the
colours just in case

9. The procedure
6. Set sampling rate on computer to 400/s
7. Set time axis compression to 10:1
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10. The procedure
8. Check the patient is comfortable
9. Ask the patient to sit quietly and to remain as still as
possible for about a minute
10. Click the start button
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11. The procedure
11. Once you have at least 10 cycles then stop
recording
12. Disconnect the leads from the patient
12. Thank the patient for their cooperation

12. Analysing the ECG
• Now you have your recordings
• BUT you won’t use them!
• There is an ECG trace on a separate computer
ready for you to analyse, for two reasons
– Examiners
– Good for you (in case you made a mess of your
ECG recording there’s still marks to gain)

13. Analysing the ECG
• Now it’s time to select an ECG recording from the
many on the screen
12. Select one of the leads which gives a large and
clear R wave (lead 2)
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14. Analysing the ECG
• If you still find it hard just try to see which lead has a
recording closest to the “textbook ECG”
13. Click and hold down the mouse and drag a box over
2 complete cardiac cycles, which you think are best
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15. Analysing the ECG
14. Click on the windows menu and select Zoom
Window from the drop down menu
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16. Analysing the ECG
15. You now have a zoomed in view of the two
cycles you need to analyse, but to make use of
this you need to know the theory...
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17. The ECG recording
Time (msec)
• You will be asked to measure the duration of:
– Segments
– Intervals

18. The ECG recording - Segments
P
Time (msec)
• The P-wave (P segment)
– Formed when the atria are depolarised
– Contraction of the atria occurs shortly after

19. The ECG recording - Segments
R
P
Q S
Time (msec)
• The QRS complex (QRS segment)
– Formed when the ventricles are depolarised
– Much larger due to larger size of ventricles

20. The ECG recording - Segments
R
P T
Q S
Time (msec)
• The T wave (T segment)
– Formed when the ventricles repolarise
– N.B the atria repolarise too but the signal is
shadowed by the much more powerful signal of
the QRS complex

21. The ECG recording - Segments
R
P T
Q S
Time (msec)
• The P-Q segment (P-R segment)
– The portion of the recording between P-wave and
QRS complex

22. The ECG recording - Segments
R
P T
Q S
Time (msec)
• The S-T segment
– The portion of the recording between the QRS
complex and the T-wave

23. The ECG recording - Intervals
R
P T
Q S
Time (msec)
• The P-R interval
– Misleading
– From beginning of P to beginning of Q

24. The ECG recording - Intervals
R
P T
Q S
Time (msec)
• The Q-T interval
– From beginning of QRS complex to end of T

25. The ECG recording - Intervals
R R
P T P
Q Q S
S
Time (msec)
• The T-P interval
– From end of T to beginning of P on next wave

26. Analysing the ECG
16. Place the marker (M) at the beginning of the
segment or interval you are asked to measure
(e.g. P-R interval)
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27. Analysing the ECG
17. Move the cursor along the trace to the end
of the segment or interval you are asked to
measure (e.g. P-R interval)
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28. Analysing the ECG
18. Now record the time from the top of the window
19. Tell the examiner your result and you’re done!!!
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29. Measuring Heart Rate using the ECG
• Change the time-axis compression to 50:1
• Again, use a lead on the ECG that is clear
• Highlight 15 seconds worth of graph
File View Windows Macro Help 400/s
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30. Measuring Heart Rate using the ECG
• Count the number of QRS complexes within
the selection
• Multiply this number by 4...and you have your
answer!
File View Windows Macro Help 400/s
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31. The ECG station
• Easy marks
• This skill is rarely given alone, so when
practicing get the quickest time possible
• Make sure you know the theory inside out
• Practice makes perfect
• Act as if you would with a real patient

32. Any Questions?
GOOD LUCK!!!!!