Electrocardiography

1. Electrocardiogram
⚫ECG is the record of the electrical activity of the heart.
⚫Electrical activity precedes the mechanical activity of the
heart.
⚫Atria and ventricles have separate electrical activity.
⚫Electrical activity has two phases: phase of depolarisation
and phase of repolarization.

2. 1. To recognize arrhythmias
2. To diagnose miscellaneous conditions like
3. To diagnose Ischaemia
1. Electrolyte imbalance
2. WPW Syndrome
4. To diagnose chamber hypertrophy
1. Various channelopathies
2. Certain heart diseases have classical ECG pattern
Uses of ECG

3. ECG: Descriptive terms
Electrocardiogram has:
Waves
Segments
&
Intervals

4. ECG – Waves
⚫ Wavesare tracings which aredeflections aboveor
below the baseline.
⚫ Wave indicate a specific electrical activity
P - Atrial depolarisation
QRS- Ventricular depolarisation
T - Ventricular repolarisation
Ta - Atrial depolarisation
U - After potential/papillary muscle
repolarisation/ Purkingie system
repolarisation

5. ECG – Waves (Contd..)
Q. -
R. -
S. -
In QRS complex if the first deflection
is negative – that is named ‘q’ wave
First positivedef lection in QRS
complex
Negativewave following ‘R’ wave

6. ECG segments
Segments are Isoelectric. Thereare 3 segments in
an ECG.
⚫PR segment -
⚫ST segment -
⚫TP segment -
End of P wave to
beginning of QRS complex
End of QRS complex to
beginning of T wave
End of T to beginning of P
wave

7. ECG Intervals
⚫Includewavesand segments
⚫Indicatespecific time period in cardiac cycle
PR interval – Beginning of P to beginning of QRS
⚫Indicate AV conduction time
⚫Include P waveand PR segment
QT interval - Beginning of QRS complex
toend of T wave
⚫Indicate Electrical systole

9. Recording of Electrocardiogram
- LI/LII/LIII
aVR/aVL/aVF
Leads:-
Limb leads:
Bipolar limb lead
Unipolar limb leads-
Chest leads:
Unipolar chest leads - V1 – V6

10. Recording of Electrocardiogram
⚫ Standardisation
1 small divisionvertically
- 1mv = 10 divisionsvertically
- 0.1 mv
Depending on the size of of QRS complex the
standardizationcan bechanged to twiceor half.
⚫ Speed of recording – 25mm/sec
1 small division horizontally - 0.04 sec
⚫ Sometimes 50 mm/sec recording is useful toseparate
outwavesespecially in tachycardia (Rarely used)

11. Interpretation of Electrocardiogram
Stepwiseanalysis -
⚫ Standardization
⚫ Heartrate
- Is itcorrect?
- 1500
r-r interval
⚫ P waves - Is itsinus ‘P’ wave
Size & shape – normal or not
⚫ PR interval - Is it normal?
⚫ QRS complex - Duration
⚫ Abnormal Q wave
⚫ Heightof R wave
⚫ Depth of S wave

12. ⚫ Duration
Deviation
⚫ T wave
ST segment -
-
-
⚫ U wave -
Upright, flat,
inverted
Prominentor not