The document discusses electrocardiography (ECG), which records the electrical activity of the heart. It describes how the ECG is formed based on the direction of current flow and the placement of electrodes. The standard 12-lead ECG is described, including limb leads, augmented limb leads, and chest leads. Common ECG patterns such as the P wave, QRS complex, and ST segment are defined. Various cardiac arrhythmias and conduction abnormalities are also summarized, including sinus arrhythmia, heart block, bundle branch block, and atrial fibrillation.

2. Aga Khan University
Dr. Nasir Mustafa

3. ECG
ELECTROCARDIOGRAM
STORY OF HEART

4. ECG :
Electrocardiography is the technique of recording the
electrical activity of heart. The recording itself is
called electrocardiogram. The machine is called
Electrocardiograph.

5. RULES OF ECG. FORMATION
◼ HEART BEHAVES AS A SINGLE UNIT
◼ CURRENT FLOWS FROM NEGATIVE TO POSITIVE DIRECTION.
◼ CURRENT MOVING TOWARDS ELECTRODE SHOWS POSITIVE
DEFLECTION.
◼ CURRENT MOVING AWAY SHOWS A NEGATIVE DEFLECTION.
+-

6. RULES OF ECG. FORMATION
➢ CURRENT IN THE MIDDLE OF ELECTRODE
SHOWS AN ISOELECTRIC DEFLECTION.
➢ DURING RESTING STATE
HEART IS POSITVELY CHARGED OUTSIDE.
➢ DURING DEPOLARISED / INFRACTED
STATE IT IS NEGATIVELY CHARGED OUTSIDE
+++
+++
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7. ECG TRACINGS:
❑ The cardiac conduction
moves in a waves from.
❑ The three peaks and two
through were given the
name of a PQRST complex.
❑ Taking this wave in a
triangle gave the PQRST
complex its present picture.
❑ The complex P, R and T
always remain upright
where as Q and S remains
negative .
P
P
Q
Q
S
R
R
S
T
T

8. ECG TRACINGS:
The shape of PQRST complex depends on time taken by
the heart to depolarize and repolarize again.

9. ECG ( Depolarization Mode )
NORMALLY THE CURRENT IS
GENERATED IN THE SA NODE
AND FANS OUT TO DEPOLARISE
THE ENTRIE HEART.
SA Node

10. EINTHOWINS TRIANGLE
TO CAPTURE THE WHOLE
MODE OF DEPOLARISATION
EINTHOWINS TOOK THE HEART
IN A TRIANGLE MAKING USE
OF THE LIMBS AS HIS POSITIVE
AND NEGATIVE POLES.

11. Naming and placement of leads
◼ Lead I- b/w Rt. arm
& Lt. arm.
◼ Lead II- b/w Rt. arm
& Lt. foot.
◼ Lead III b/w Lt. arm
& Lt. foot.
.I
.II .III

12. THE AUGMENTED LEAD (a.V.)
UNIPOLAR LIMB LEADS.
❖ Neutralizing the current at
two other poles the maximum
current at one pole is
recorded.
❖ aVR recording current at the
right pole.
❖ aVL recording current at the
left pole.
❖ aVF recording current at the
foot.
Lead I
Lead II Lead III
aVR aVL
aVF

13. UNIPOLAR CHEST LEADS
IN THE RECENT PAST
SCIENTIST HAVE
INTRODUCED 6
UNIPOLAR CHEST
LEADS (VI-V6),TO
RECORD THE ENTIRE
TROLATERAL AREA
V1
V2
V3
V5
V6
V4

14. CHEST LEAD PLACEMENT
CHEST LEADS
◼ VI: 4th intercostal space
3 cms right of midline.
◼ V2: 4th intercostal
space 3 cms left of midline.
◼ V3: space between 2nd
and 4th chest leads
◼ V4: 5th intercostal
space mid clavicular line.
◼ V5: 5th intercostal
space anterior axillary line
◼ V6: 5th intercostal
space mid axiliary line.
V1 V2
V3
V4 V5V6

15. CURRENT ECG MODEL
THE CURRENT ECG MODEL
COMPRISES OF:
BIPOLAR LIMB LEADS:
I, II & III.
AUGMENTED UNIPOLAR
LIMB LEADS:
a VR.aVL. aVF
UNIPOLAR CHEST LEADS:
VI-V6.or C1-C6
.I
.II .III
aVLavR
aVF
V1 V2
V3
V4
V5
V6

16. Lead representation in a circle
So the lead placement
in a circle will have
following pattern
Lead I = 00
Lead aVR = +300
Lead II = +600
Lead aVF = +900
Lead III = +1200
Lead aVL = -300

17. AREA REPRESNATION BY ECG
◼ INFERIOR
Leads II, III & aVF
◼ ANTEROSEPTAL
Leads V1,V2,V3 & V4
◼ LATERAL
I, aVL, V5 & V6
V1
V5
V6V3
V2
V4
IaVR
aVL
aVF
II
III

18. THREE STEP RULE
The depolarization of the
ventricles occurs via three
step rule
1. Depolarization of IVS.
2. Depolarization of RV.
3. Depolarization of LV.
1
2
3

19. ‘R’ Wave Progression
The ECG shows gradual
progression of ‘R” wave
Through V1 to V6 as the
conduction fans
out in the ventricles.

20. ECG PARAMETERS
1 sm sq =.04sec./40msec. or1/1500 of a second
5 sm.sq.= 0.20 sec/200m.sec/300 0f a second
1 sm.sq = 1mm in height or 0.1 mV
10 sm.sq = 10mm in height or 1 mV

21. ECG TRACINGS:
Normal values of a PQRST complex
Duration Height
P WAVE: 0.08 seconds 2 mm
PR segment: 0.12-0.20 isoelectric
Q wave: < 0.04 sec < 1/3rd of R
QRS complex: 0.06-0.10 sec 5-20mm
10-27mm
ST segment: 15 degrees above the
isoelectric line
S wave < 1/3rd of R
QT interval: 0.36-0.42 sec
QT: QT corrected according to the
heart rate.

22. READING AN ECG
* Rate
* Rhythm
* Axis
* P wave
* P-R interval
* Q wave
* QRS complex
* S wave
* ST segment
* T wave
* U wave

23. HEART RATE / min
◼ For regular rhythm: 1500 /No of small squares b/w 2RR’
◼ For irregular rhythm: No of R waves in a 6 second strip x 10.
R
R’
1 2 3 4 5 6
10 sm. sq

24. STAGES OF ISCHEMIA
Normal
<50%
ST flatting
>50%
ST .& T
>70%
2mm ST
>80%v
>2mm ST
>90% 100%
T inversion
>60%
Changes in ECG that occur roughly with the
amount of obstruction present in the vessels

25. ACUTE M.I.
Normal S-T Elevation Reciprocal depression
Acute MI < 4-6 hours is diagnosed on the presence of
ST elevation in more than 2 contiguous leads
with reciprocal changes in any other area
opposite to the area of ischemia

26. AGE OF MI
In a transmural infarct the ‘R’ wave is buried
down below the base line changing into a ‘Q’
wave which persists throughout the patients life
representing a dead scar over the infarcted area.
<4-6 Hours >6 Hours 24 Hours 72 Hours 1 week 1 month

27. DYSRHYTHMIAS
DISTURBANCE IN NORMAL RHYTHM
CONDUCTION PHYSIOLOGY
Heart behaves as a single unit.
Normally the conduction arises
from the SA node, then it
reaches the AV node and after
depolarizing the node it travels
down the his bundle and fans
out into the Right and the Left
bundle reaching finally the
Perkingi fibers and the
Endocardium
SA Node
AV Node
Lt.Bundle
Rt.Bundle

28. DYSRHYTHMIAS
1. S.A. Nodal dysrhythmias
2. A.V. Nodal dysrhythmias
3. His bundle dysrhythmias
4. Atrial dysrhythmias
5. Ventricular dysrhythmias
1.SA Node
2.AV Node
Dysrythmias can arise from any ectopic focus along this
conduction pathway or from the myocardium characterize as
3 His bundle
5 Ventricle
4 Atrial

29. SINUS ARRYTHMIA
P wave Normal
P-R interval Normal
QRS Complex Normal
T wave Normal
R-R’ interval Varies with
respiration
ExpirationInspirationExpiration
Heart Rate varies with respiration, it increases during inspiration due
to increase in venous return to the right side of the heart and decreases
during expiration vice versa

30. SINUS ARREST
P wave Normal
P-R interval Normal
QRS Comp. Normal
T wave Normal
R-R’ interval > 2
normal RR’ complexes
SA node arrest of
> 2 RR’ complex
SA node disease causing failure to form impulse of more than two RR
Complexes Arrest of more than 3 seconds causes syncope.
Arrest of more than 5 seconds causes unconsciousness.
Arrest of more than 10 seconds causes convulsions.

31. AV NODAL DYSRHYTHMIAS
Disease of the AV node resulting in an abnormal delay in the
conduction of impulse from the atria to the ventricle which is
classified as degree of A/V block according to the delay.
1- I0 Block.
2- II0 Block a. Mobitz Type I block( Wenkebach phenomonon)
b. Mobitz Type II block
3- III0 Block or Complete Heart Block

32. I0 HEART BLOCK
Heart Rate More than 100 bpm.
P wave Normal
P-R interval > 0.20 sec
QRS Complex Normal
T wave Normal
R-R’ interval Normal
A delay in the conduction of an impulse through the A/V node
resulting in the prolongation of P-R interval of > 0.20 seconds.
P P P PP

33. Mobitz Type I Block
P wave Normal
P-R interval Progressive
prolongation terminating in
drop in QRST complex
QRS Complex Frequent
drop though normal.
T wave Normal
R-R’ interval Variable
P P P P P P
Disease in the A/V node causes a delay in impulse conduction
through the A/V node resulting in the progressive prolongation of
P-R interval terminating in a drop in QRST complex.
Drop in PQRST

34. Mobitz Type II Block
P wave Normal
P-R interval Normal
QRS complex Regular
drop though normal
T wave Normal
R-R’ interval Normal
P P P P P P P P P
Disease in the A/V node causes a delay in impulse conduction
resulting in a regular drop in a whole QRST complex.

35. III0 / Complete Heart Block
P P P P P P P P P P P
Disease in the A/V node causes a delay in impulse conduction
to such an extent that atria loose association with the ventricles
and both beat on their own individual rate.
P wave 75 bmp.
But normal
P-R interval Inconstant
QRS Complex Multiple drops
T wave Normal
R-R’ interval Variable

36. HIS BUNDLE BLOCK
1 -I0 Block b/w SA & AV node
2 -RBBB
3 -LAD (Left anterior hemiblock)
4 -RAD ( Right posterior Hemiblock)
1
2
3
4
I0 Block
RBBB
LAD
RAD
AF
PF

37. ATRIAL FIBRILLATION
Atrial Rate 400-600 bpm
Ventr.Rate 45-180 bpm
P wave replaced by
‘f ’ wave
PR interval absent
QRS Complex Normal
T wave Normal
R-R’ interval Variable
‘f’ waves
Dilatation of atria produces numerous ectopic foci, which send
their impulses at the A/V node. The one that escapes
through, results in ventricular depolarization