ECG
Dr. Hassan Ahmed Raaqi
cardiology specialist Ain Shams University
What is ECG (Electrocardiogram)?
An ECG is the recording (“gram”) of the
electrical activity (“electro”) generated by
the cells of the heart (“cardio”) that
reaches the body surface.
 ECG is a representation of the heart's
electrical activity recorded from electrodes
on the body surface

ECG leads
Limb leads
 I
 II
 III
 aVF
 aVL
 aVR
Chest leads
 V1
 V2
 V3
 V4
 V5
 V6
ECG leads placement
Components of ECG
Calculation. of heart rate
1500 method
Divide 1500 by the number of small squares
Between two consecutive R-R waves
= 1500/no of small squares
For ex 1.
Here, there are 20 small squares
Between 2 consecutive RR
So 1500/20 = 75 b/m
For ex 2
Here total number of small boxes are 30
So 1500/ 30 = 50 b/m
6 second method
↓
↓↓
2
3
↓
4
↓
5
↓
In a 6 second strip,count the number of
QRS complexes and multiply it by 10
So here 10 QRS x 10 = 100 b/m
1 small square = 0.04 sec
5 small square = 0.2 sec
5 large squares = 1 sec
30 large squares = 6 sec
↓
6
↓
Sinus Arrhythmia
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