The ECG records the depolarization and repolarization potentials generated by the atrial and ventricular myocardium over time. It shows:
- Atrial depolarization as the P wave
- Ventricular depolarization as the QRS complex
- Ventricular repolarization as the ST segment, T wave, and U wave.
4. ECG graph paper
4
Horizontal axis
Records the time (interval) between cardiac electrical
events
Vertical axis
Records their amplitude (voltage)
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18. Atrial repolarization
18
Usually too low in amplitude to be detected.
Obscured by QRS (i.e., ventricular depolarization).
May be apparent in
Acute pericarditis
Atrial infarction.
Atrial depolarization causes P wave.
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19. Summary
19
Atrial depolarization
P wave.
Ventricular depolarization
QRS complex
Ventricular repolarization
ST segment, T wave, and U wave.
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20. ECG waves
20
P
Atrial
depolarization.
R
Ventricular depolarization and atrial
repolarization.
QRS complex
Ventricular depolarization
ST - T - U complex
Ventricular repolarization
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23. Bipolar lead
23
Measures the difference in
potential between electrodes at two
extremities
Lead
I = left arm-right arm voltages
Lead II = left leg-right arm
Lead III = left leg-left arm.
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29. V 1 to V 6
29
6 unipolar chest
leads or precordial
leads.
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30. 3 augmented unipolar limb leads
30
avL, avR, and avF.
Recordings between one limb
and the other 2 limbs.
Increases the size of the
potentials by 50 %.
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