This document contains questions and information about electrocardiography (ECG) asked by Muhammad Awais Munir, a student at Punjab Medical College. It includes questions about what ECG stands for, who invented it, myocardial infarction patterns on ECG, the heart's conduction system, sinus rhythm, pacemakers, electrodes, ECG waves, interpreting ECGs, calculating heart rate from ECG, determining electrical axis, identifying different heart walls on ECG leads, and more. Diagrams are provided to illustrate the heart's conduction system, ECG paper measurements, hexaxial arrays for determining electrical axis, and pacemaker modes. Guidelines for pacemaker implantation in acquired atrioventricular block are also summarized.

1. Muhammad Awais Munir
Roll # 346
Batch 2011-2016
Punjab Medical College
Faisalabad

2.  What does ECG stands for?
 Who first invented ECG?
 Who first described Myocardial infarction on
ECG?
 What is the conduction system of the heart?
 What is a sinus rhythm?
 What is pacemaker?
 What is ectopic pacemaker?

3.  What is an electrode?
 What is a positive deflection on ECG?
 What is a negative deflection on ECG?
 What are the waves in an ECG?
 How to interpret an ECG?

4.  How to calculate heart rate from an ECG?
 How to determine electrical axis of heart
from an ECG?
 Which leads represent anterior wall?
 Which leads represent lateral wall?
 Which leads represent inferior wall?
 Which leads represent right ventricle?
 Which leads represent posterior wall?

20.  SA node
 Atrial pathways
 AV node
 Bundle of His
 Bundle branches
 Left
▪ Left anterior faasciculus
▪ Left posterior fasciculus
 Right
 Purkinje Fibers

21. The Electrical System of the Heart
AV Node
Posterior Inferior Fascicle
Anterior Superior Fascicle
Septal Depolarization
Fibers
Purkinjie Fibers
Inter- nodalTracts
Bundle of HIS
Left Bundle
Branch
Right Bundle
Branch
SA Node

22. SA
Node
AV
Node
Inter-nodal
Tract
Bundle
of Kent
James Fibers
Conduction System of
the Heart:
A Conceptual Model
for Illustration
Bundle
of HIS
Right
Bundle
Branch
Left
Bundle
Branch
Septal
Depolarization
Fibers
Anterior
Superior
Fascicle
Posterior
Inferior
Fascicle

23.  P wave
 atrial depolarisation.
 ‘sinus rhythm’
 PR interval
 conduction through the AV node and the bundle of His.
 This should be between 120–200 ms
 QRS complex
 depolarisation of the ventricles.
 A Q wave is any negative deflection at the beginning of a QRS
complex.
 Small Q waves in some leads may be normal.
 Large Q waves (> 2 mm) may be abnormal.
The EKG, or a measure of this electrical activity of the heart, is
comprised of 3 primary parts...

24.  R wave
 first positive deflection
 S wave is the negative deflection immediately
following an R wave.
 The QRS complex < 120 ms (3 mm)
 ST segment
 ‘Isoelectric’
 T wave
 Repolarisation of the ventricles.

25. The ECG Complex with Interval and Segment Measurements

26. Lead I
extends from
the right to the
left arm
Lead II
extends from the
right arm to the
left foot
Lead III
extends from the left
arm to the left foot
+-
+
-

27. +
-
G
Electrocardiograph
Lead II
The Concept of a “Lead”

28. +
-
The Concept of a “Lead”
Lead II
G

29. +-
RA
RA
LL
+
+
--
LA
LL
LA
LEAD II
LEAD I
LEAD III
The Concept of a “Lead”
Leads I, II, and III

30. The Concept of a “Lead”
+
-
+
+
-
LEAD aVR
-
LEAD aVL
LEAD aVF
By combining certain limb
leads into a central
terminal, which serves as
the negative electrode,
other leads could be
formed to "fill in the gaps"
in terms of the angles of
directional recording.
These leads required
augmentation of voltage
to be read and are thus
labeled.
AugmentedVoltage Leads
AVR,AVL, and AVF

31. 0o
LEAD aVR LEAD aVL
LEAD aVF
LEAD II
LEAD I
LEAD III
60o
90o120o
-30o-150o
Each of the limb
leads (I, II, III,AVR,
AVL, AVF) can be
assigned an angle of
clockwise or
counterclockwise
rotation to describe
its position in the
frontal plane.
Downward rotation
from 0 is positive and
upward rotation
from 0 is negative.
The Concept of a “Lead”
Summary of the
“Limb Leads”

32. V4 V5 V6
V1 - 4th intercostal space - right margin of sternum
V2 - 4th intercostal space - left margin of sternum
V3 - linear midpoint betweenV2 andV4
V4 - 5th intercostal space at the mid clavicular line
V5 - horizontally adjacent toV4 at anterior axillary line
V6 - horizontally adjacent toV5 at mid-axillary line
Each of the 6
precordial leads is
unipolar (1 electrode
constitutes a lead)
and is designed to
view the electrical
activity of the heart in
the horizontal or
transverse plane
The “Precordial Leads”
4th
intercostal
space
The Concept of a “Lead”
V2V1
V3

33. Read
Book
Good
Your

35. • Leads II, III, aVF
- Looks at inferior heart wall
View of Inferior Heart Wall
-Looks from the left leg up

36. • Leads I and aVL
– Looks at lateral heart wall
– Looks from the left arm toward
heart
View of Lateral Heart Wall
*Sometimes known as High Lateral*

37. • Leads V5 & V6
– Looks at lateral heart wall
– Looks from the left lateral chest
toward heart
View of Lateral Heart Wall
*Sometimes referred to as
Low Lateral or Apical view*

38. • Leads I, aVL, V5, V6
- Looks at the lateral wall of the heart from two
different perspectives
View of Entire Lateral Heart Wall
Lateral Wall

39. • Leads V3, V4
– Looks at anterior heart wall
– Looks from the left anterior chest
View of Anterior Heart Wall

40. • Leads V1, V2
- Looks at septal heart wall
- Looks along sternal borders
View of Septal Heart Wall

41.  Speed = 25mm/second
 1 small box(x-axis) =1mm = .04 second
 1 large box (x-axis)=5mm = 0.2 second
 1second = 5 large boxes
 1small box(y-axis)=1mm=0.1mV
 1 large box (y-axis)=5mm = 0.5mV
 2 large boxes (y-axis) = 1 mV

43. ECG Paper and related Heart Rate &Voltage Computations
Memorize
These 2

44.  Rate
 Rhythm
 Axis
 Ischemia/Infarction
 Hypertrophy
 Block

45. 1.R-R interval
Is it regular or irregular?
2.What is the heart rate?
300, 150, 100, 75, 60, 50
300 / (No of large boxes between two consecutive
R waves)
1500 / (No of small boxes between two consecutive
R waves)
Count the number of cardiac cycles in 10 seconds
(50 Large boxes) and multiple by 6.

46. Bradycardia
Less than 60 bpm
Tachycardia
Greater than 100 bpm

49.  Regular
 Irregular

50.  Normal Axis
 LeftAxis Deviation
 Right Axis Deviation

59. Hexaxial Array for Axis Determination
determination of the
angle of the
HEART AXIS in the
frontal plain

60. Lead I
If lead I is mostly
positive, the
axis must lie in the
right half of
of the coordinate
system (the main
vector is moving
mostly toward the
lead’s positive
electrode)
Hexaxial Array for Axis Determination – Example 1

61. If lead AVF is mostly
positive, the
axis must lie in the
bottom half of
of the coordinate
system (again, the
main vector is
moving mostly
toward the lead’s
positive electrode
Lead AVF
Hexaxial Array for Axis Determination – Example 1

62. Hexaxial Array for Axis Determination – Example 1
I AVF
Combining the two
plots, we see
that the axis must lie
in the bottom
right hand quadrant

63. I AVF AVL
Hexaxial Array for Axis Determination – Example 1
Once the quadrant has
been determined, find the
most equiphasic or
smallest limb lead. The
axis will lie about 90o away
from this lead. Given that
AVL is the most
equiphasic lead, the axis
here is at approximately
60o.

64. Hexaxial Array for Axis Determination – Example 1
Since QRS complex in
AVL is a slightly more
positive, the true axis will
lie a little closer to AVL
(the depolarization vector
is moving a little more
towards AVL than away
from it). A better
estimate would be about
50o (normal axis).
I AVF AVL

65. Hexaxial Array for Axis Determination – Example 2
Lead I
If lead I is mostly
negative, the
axis must lie in the
left half of
of the coordinate
system.

66. Hexaxial Array for Axis Determination – Example 2
Lead AVF
If lead AVF is mostly
positive, the
axis must lie in the
bottom half of
of the coordinate
system

67. I AVF
Combining the two
plots, we see
that the axis must lie
in the bottom
left hand quadrant
(Right Axis
Deviation)
Hexaxial Array for Axis Determination – Example 2

68. Hexaxial Array for Axis Determination – Example 2
I AVF II
Once the quadrant has
been determined, find
the most equiphasic or
smallest limb lead.
The axis will lie about
90o away from this
lead. Given that II is
the most equiphasic
lead, the axis here is at
approximately 150o.

69. Hexaxial Array for Axis Determination – Example 2
I AVF II
Since the QRS in II is a
slightly more negative,
the true axis will lie a
little farther away
from lead II than just
90o (the depolarization
vector is moving a
little more away from
lead II than toward it).
A better estimate
would be 160o.

70. Since Lead III is the
most equiphasic
lead and it is
slightly more
positive than
negative, this axis
could be estimated
at about 40o.
Precise calculation
of the axis can be
done using the
coordinate system
to plot net voltages
of perpendicular
leads, drawing a
resultant rectangle,
then connecting the
origin of the
coordinate system
with the opposite
corner of the
rectangle. A
protractor can then
be used to measure
the deflection from
0.
Net voltage = 12
Netvoltage=7
Precise Axis
Calculation

71.  T wave inversions
 ST segment depression
 ST segment Elevation
 Q-waves

77.  1st degree heart block
 2nd degree heart block
▪ TYPE 1
▪ TYPE 2
 3rd degree heart block
 LBBB
 LAH
 LPH
 RBBB

79.  Causes 1st Degree heart block
 Effect of drugs
 Beta Blockers
 Calcium Channel Blockers
 Digitalis
 Increased vagal tone
 Inferior wall ischemia/infarction
 No treatment is required for 1st degree heart
block until it is symptomatic
 Atropine can used to treat bradycardia

80. ?

81.  Most commonly due to intranodal pathology
 No treatment is required until the patient is
syptomatic
 Atropine can be used to treat bradycardia

83.  Commonly due to infranodal pathology
 Pacing is usually needed as there is more
chance ofprogressing to a higher block

85.  Temporary or permanent artificial pacing is the
most reliable treatment for patients with
symptomatic AV conduction system disease.
 Correction of electrolyte derangements
 Ischemia
 inhibition of excessive vagal tone
 withholding drugs with AV nodal blocking properties
 Adjunctive pharmacologic treatment with
atropine or isoproterenol
 Transcutaneous pacing
 Permanent pacemaking.

86.  Pacemaker modes and function are named using a
five-letter code.
 First letter indicates the chamber(s) that is paced (O, none;
A, atrium;V, ventricle; D, dual; S, single)
 Second is the chamber(s) in which sensing occurs (O,
none; A, atrium;V, ventricle; D, dual; S, single)
 Third is the response to a sensed event (O, none; I,
inhibition; T, triggered; D, inhibition + triggered)
 Fourth letter refers to the programmability or rate
response (R, rate responsive)
 Fifth refers to the existence of antitachycardia functions if
present (O, none; P, antitachycardia pacing; S, shock; D,
pace + shock).

87. Guideline Summary for Pacemaker Implantation in Acquired AV Block
Class I
1.Third-degree or high-grade AV block at any anatomic level associated with:
a. Symptomatic bradycardia
b. Essential drug therapy that produces symptomatic bradycardia
c. Periods of asystole > 3 s or any escape rate < 40 beats/min while awake
d. Postoperative AV block not expected to resolve
e. Catheter ablation of the AV junction
f. Neuromuscular diseases such as myotonic dystrophy, Kearns-Sayre syndrome, Erb dystrophy, and
peroneal muscular atrophy, regardless of the presence of symptoms
2. Second-degree AV block with symptomatic bradycardia
3.Type II second-degree AV block with a wide QRS complex with or without symptoms
Class IIa
1. Asymptomatic third-degree AV block regardless of level
2. Asymptomatic type II second-degree AV block with a narrow QRS complex
3. Asymptomatic type II second-degree AV block with block within or below the His at electrophysiologic
study
4. First- or second-degree AV block with symptoms similar to pacemaker syndrome

88. Class IIb
1. Marked first-degree AV block (PR interval > 300 ms) in patients with LV dysfunction in whom shortening
the AV delay would improve hemodynamics
2. Neuromuscular diseases, such as myotonic dystrophy, Kearns-Sayre syndrome, Erb dystrophy, and
peroneal muscular atrophy, with any degree of AV block regardless of the presence of symptoms
Class III
1. Asymptomatic first-degree AV block
2. Asymptomatic type I second-degree AV block at the AV node level
3. AV block that is expected to resolve or is unlikely to recur (Lyme disease, drug toxicity)

89.  Class I
 Conditions in which permanent pacing is definitely beneficial,
useful, and effective. In such conditions, implantation of a
cardiac pacemaker is considered acceptable and necessary,
provided that the condition is not due to a transient cause.
 Class II
 Conditions in which permanent pacing may be indicated but
there is conflicting evidence and/or divergence of opinion; class
IIA refers to conditions in which the weight of evidence/opinion
is in favor of usefulness/efficacy, while class IIB refers to
conditions in which the usefulness/efficacy is less well
established by evidence/opinion.
 Class III
 Conditions in which permanent pacing is not useful/effective
and in some cases may be harmful.

90.  Tall R wave in v1 usually notched with an RSR’
pattern
 Prominent, delayed and widened S wave in I,
V5,V6
 QRS complex duration more
than0.14seconds

92.  Widening of QRS complex (QRS > 0.12
seconds)
 Left axis Deviation(usually)
 M pattern in I,V5,V6
 The S-T segment andT wave are opposite to
the terminal QRS deflection

94.  Left axis deviation
 Deep S waves in II, III(More) and aVf
 Tall R wave in aVL
 Prominent initial q wave in I and aVL
 Prominent initial r waves in II, III and aVF
 Increased ventricular activation time >0.045
seconds
 QRS complex < 0.11seconds
 Slight surring or R waves in aVR and I and S
waves inV5,V6
 Increase QRS deflexions in frontal leads
 Secondary t wave repolarization changes

96.  Right Axis Deviation
 Prominent S waves in I,aVL
 Tall R waves in II, III(tallest),aVF
 Prominent q wave in II, III, aVF and a small r
wave in I
 Tall R wave in III is frequently notched or
slurred

98.  LVH
 RVH
 RAH
 LAH

99.  Magnitude of S wave inV1,V2
Plus
 Magnitude of R wave inV5,V6
 Or
 S wave inV1,V2>20mm
 R wave inV5,V6> 20mm
 Or
 R wave in standard limb lead I > 15mm
 Or
 S wave in aVL >11mm
 Or voltage of all 12 limb leads >175mm
>35mm

100.  Attenuation of the small initial q wave in left
orientated leads
 Increased left ventricular activation time>
0.045seconds
 Small equiphasic rs complex in aVF
 Counter clockwise rotation of electrical axis
 Transition shifts to right in leadV2,V3

101.  ST-T segment changes(left ventricular strain
pattern)
 Inverted U waves in left precordial leads
 Left atrialenlargement
 QRS axis at 00 andT wave axis at 1800

102.  IncreaedQRS magnitude=3
 ST-T wave abnormality=3
 Pwave of left atrial enlargement=3
 Left axis deviation=2
 increasedVAT=1
 >5 indicates LVH

104.  Right axis deviation
 Dominance of R wave in right orientated
leads(V1)
 R:S ratio > 1 inV1
 R or R’ > 5mm inV1
 Initial incident of QRS complex inV1
 Initial slur of QRS
 Initial deflexion separated from R wave by a
notch
 Initial qR complex inV1

105.  VAT> 0.02 seconds
 diminution of R wave towards left orintated
leads
 Transition zone shifts towards leftV4,V5
 Right bundle branch block
 Right ventriculat strain pattarn(t-wave
inversions and ST-segment minimally depressed
with slight upward convexity inV1-V4)
 Diminished U-wave in right precordial
lead/inverted in II, III, aVF
 Right atrial enlargement(tall/peaked p wave in II)

107.  LVH with right axis deviation
 LVH with left shift of transition zone
 LVH with tall R wave inV1
 These three constitute katz-wachtel phenomenon
 Pwave with LAH with any of the following
 R:S inV5,V6<1
 S wave inV5,V6>7mm
 Right axis deviation +900

108.  Wide and notched p waves in standard lead I
and a prominent delayed terminal deflexion
of the p wave in leadV1

109.  In lead II two types of P-wave abnormalities
can be seen.
 Right atrial enlargement is seen as a taller
than normal P-wave( increased amplitude)
 Left atrial enlargement seen as a P-wave with
a notch in it.

110. 3/23/2016
1
1
0
Note the larger terminal portion