Ecg 1

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
-

A
x
is

A
m
p
lit
u
d
e

in

m
ill
v
o
lt
s

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
V
1
Septal
V
4
Anterior
II
Inferior
aVL
Lateral
V
2
Septal
V
5
Lateral
III
Inferior
aVF
Inferior
V
3
Anterior
V
6
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
largeV
max
.
Due to opening of fast Na
+
channels.
(b) Normal SA & AV node - slow upstroke and
reduced V
max
.
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. LA
RA
LL
ECG Recordings (QRS Vector pointing leftward, inferiorly
& posteriorly)
3 Bipolar Limb Leads:
I = RA vs. LA (+)

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

23. LA
RA
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. LA
RA
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. LA
RA
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. LA
RA
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. V
1 V
2
V
3
V
4
V
5
V
6
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 V
1
through position V
6
.

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