1. What is an ECG?
• The electrocardiogram (ECG) is a graphic
recording of the electrical potentials
produced in association with the heart
beat.

2. Uses
• Chamber hypertrophy
• MI
• Arrhythmias
• Pericarditis
• Systemic diseases
• Effect of drugs
• Electrolyte imbalance

3. ECG Graph Paper
X- Axis time in seconds
Y-AxisAmplitudeinmillvolts

5. +
+ +
- - -
ECG Bipolar Limb Leads
R L
F
R
F
L

6. • Standard ECG is recorded in 12 leads
• Six Limb leads – I, II, III, aVR, aVL, aVF
• Six Chest Leads – V1 V2 V3 V4 V5 & V6
• I, II and III are called bipolar leads
• I between LA and RA
• II between LF and RA
• III between LF and LA
ECG Bipolar Limb Leads

7. ECG Unipolar Limb Leads
++
+
Lead aVR Lead aVL Lead aVF
R L
F

8. • aVR, aVL, aVF are called
unipolar leads
• aVR – from Right Arm Positive
• aVL – from Left Arm Positive
• aVF – from Left Foot Positive
ECG Unipolar Limb Leads

9. ECG Chest
Leads

10. The Six Chest
Leads
TRANSVERSE PLANE

11. Precordial (chest) Lead Position
• V1 Fourth ICS, right sternal border
• V2 Fourth ICS, left sternal border
• V3 Equidistant between V2 and V4
• V4 Fifth ICS, left Mid clavicular Line
• V5 Fifth ICS Left anterior axillary line
• V6 Fifth ICS Left mid axillary line
ECG Chest
Leads

12. Precordial Leads

13. Anatomic Groups
(Summary)
I
Lateral
aVR
None
V1
Septal
V4
Anterior
II
Inferior
aVL
Lateral
V2
Septal
V5
Lateral
III
Inferior
aVF
Inferior
V3
Anterior
V6
Lateral

14. Other Leads
• V7: Posterior Axillary Line
• V8: Posterior Scapular Line
• V9: Left border of the spine
• V3R-9R: Right Sided Leads (V2R = V1)
• VE: Ensiform cartilage
• E: Esophageal lead

15. Pitfalls
• Patient Identity
• Proper relaxation
• Good contact between skin & electrode
• Proper Standardization
• Properly grounded
• Electrical Equipment

16. Pacemakers of the Heart
• SA Node - Dominant pacemaker with an
intrinsic rate of 60 - 100 beats/minute.
• AV Node - Back-up pacemaker with an
intrinsic rate of 40 - 60 beats/minute.
• Ventricular cells - Back-up pacemaker with
an intrinsic rate of 20 - 45 bpm.

18. Phases of Cardiac Action
Potential
i) Phase 0: Upstroke or rapid depolarization.
(a) Atrial and ventricular muscles and HIS and
Purkinje fibres- rapid upstroke and
largeVmax.
Due to opening of fast Na+
channels.
(b) Normal SA & AV node - slow upstroke and
reduced Vmax.
Due to opening of Ca++
channels.

19. ii) Phase 1 : Early rapid repolarization.
iii) Phase 2 : Plateau phase.
iv) Phase 3 : Final rapid repolarization.
v) Phase 4 : Resting membrane potential or
diastolic depolarization (-90mv)

21. LARA
LL
ECG Recordings (QRS Vector pointing leftward, inferiorly
& posteriorly)
3 Bipolar Limb Leads:
I = RA vs. LA (+)

22. LARA
LL
ECG Recordings (QRS Vector pointing leftward, inferiorly
& posteriorly)
3 Bipolar Limb Leads:
I = RA vs. LA (+)
II = RA vs. LL (+)

23. LARA
LL
ECG Recordings (QRS Vector pointing leftward, inferiorly
& posteriorly)
3 Bipolar Limb Leads:
I = RA vs. LA (+)
II = RA vs. LL (+)
III = LA vs. LL (+)

24. LARA
LL
ECG Recordings (QRS Vector pointing leftward, inferiorly
& posteriorly)
3 Bipolar Limb Leads:
I = RA vs. LA (+)
II = RA vs. LL (+)
III = LA vs. LL (+)
3 Augmented Limb Leads:
aVR = (LA-LL) vs. RA(+)

25. LARA
LL
ECG Recordings (QRS Vector pointing leftward, inferiorly
& posteriorly)
3 Bipolar Limb Leads:
I = RA vs. LA (+)
II = RA vs. LL (+)
III = LA vs. LL (+)
3 Augmented Limb Leads:
aVR = (LA-LL) vs. RA(+)
aVL = (RA-LL) vs. LA(+)

26. LARA
LL
ECG Recordings (QRS Vector pointing leftward, inferiorly
& posteriorly)
3 Bipolar Limb Leads:
I = RA vs. LA (+)
II = RA vs. LL (+)
III = LA vs. LL (+)
3 Augmented Limb Leads:
aVR = (LA-LL) vs. RA(+)
aVL = (RA-LL) vs. LA(+)
aVF = (RA-LA) vs. LL(+)

27. V1 V2
V3
V4
V5
V6
6 PRECORDIAL (CHEST) LEADS
Spine
Sternum

28. ECG Recordings: (QRS vector---leftward, inferiorly and posteriorly
3 Bipolar Limb Leads
I = RA vs. LA(+)
II = RA vs. LL(+)
III = LA vs. LL(+)
3 Augmented Limb Leads
aVR = (LA-LL) vs. RA(+)
aVL = (RA-LL) vs. LA(+)
aVF = (RA-LA) vs. LL(+)
6 Precordial (Chest) Leads: Indifferent electrode (RA-LA-LL) vs.
chest lead moved from position V1 through position V6.

29. Normal Impulse Conduction
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

30. Impulse Conduction & the ECG
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

31. The “PQRST”
• P wave - Atrial
depolarization
• T wave - Ventricular
repolarization
• QRS - Ventricular
depolarization

32. The PR Interval
Atrial depolarization
+
delay in AV junction
(AV node/Bundle of His)
(delay allows time for
the atria to contract
before the ventricles
contract)

34. ECG
Complex
• P Wave is Atrial contraction – Normal 0.12 sec
• PR interval is from the beginning of P wave to
the beginning of QRS – Normal up to 0.2 sec
• QRS is Ventricular contraction –Normal 0.08
sec
• ST segment – Normal Isoelectic (electric
silence)
• QT Interval – From the beginning of QRS to the
end of T wave – Normal – 0.40 sec
• RR Interval – One Cardiac cycle 0.80 sec

35. Reporting of ECG
1. Standardization
2. Rhythm
3. Heart rate
4. PR interval
5. QRS interval
6. QT/QTc interval
7. Axis
8. P wave

36. 9. Precordial R wave progression
10. Abnormal Q wave
11. ST Segment
12. T wave
13. U wave