The document provides an extensive overview of the electrocardiogram (ECG), detailing its function, nomenclature, and various waveforms associated with cardiac electrical activity. It explains the key components of an ECG, including the P wave, QRS complex, and T wave, as well as the assessment of heart rate, rhythm, and pathological conditions. Additionally, it discusses abnormal ECG findings, heart blocks, and arrhythmias, offering guidelines on how to interpret and report ECG results.

1. Electrocardiogram
‘ECG’
Zaid kamel Alhusaini, MD
Cardiology fellow
2023

2. What is ECG ?
it'sused to record the electrical
activity of the heart from different
angles to both identity and locate
pathology
Electrode are placed on different
parts of a patient’slimb and chest

3. ECG Electrodes vs ECG leads
ECG Electrodes is a conductive pad that is
attached to the skin to record electrical activity
ECG leads (= views) is a graphical representation
of the heart’s electrical activity

4. ECG leads
Limb leads
• Standard leads : I,II,III
• Augmented leads : aVR, aVF, aVL
Chest leads
V1-V2 : Septal view of the heart
V3-V4 : Anterior view of the heart
V5-V6 : Lateral view of heart

7. ECG paper is divided by heavy vertical and
horizontal lines into big squares , each big square
is subdivided into 5 small squares.
Calibration : Duration (Time) X Voltage(Amplitude)
Small square : 1mm X 1mm (40ms X 0.1mV)
Large square : 5mm X 5 mm ( 200ms X 0.5 mV )
• 5 large square = 1 second
• 300 large square = 60 second (1 minute )

8. • Before you interpret an ECG , check the
standard setting of calibration:
• Speed : 25mm/sec
• Voltage : 2 big squares = one mV = 10mm
• We can change ECG setting (speed and
voltage) according to the situation

10. ECG nomenclature
• P wave
• PR interval /segment
• QRS complex
• J point
• ST segment
• T wave
• U wave
• QT interval
• RR interval

11. P-wave
The P wave is the first positive deflection on the ECG
and represents atrial depolarization
Characteristics of the Normal Sinus P Wave
• Morphology : Smooth contour , upright in leads I
and II, inverted in aVR , Biphasic in V1
• Duration : < 120ms or 3 small squares
• Amplitude : < 2.5 mm in the limb leads , < 1.5
mm in the precordial leads

12. Common P Wave Abnormalities
• P mitrale (bifid P waves), seen with left
atrial enlargement
• P pulmonale (peaked P waves), seen
with right atrial enlargement
• P wave inversion, seen with ectopic atrial
and junctional rhythms
• Variable P wave morphology, seen in
multifocal atrial rhythms

13. PR interval
• Normal duration is 120-200 ms ( 3-5 small
square )
• Abnormally short/ long/ varying as due Heart
blocks

14. QRS complex
• Represent ventricular depolarization
• Duration(width): < 2.5 small square , wide if > 3 small
square
• Amplitude(height): Lead I+ Lead II+ Lead III > 15 small
square , can be normal/ low voltage/ alternans.
• Component :
• Q wave : First negative deflection
• R wave : First positive deflection , it show normal
progression from V1 to V5 , transitional zone (R = S) in V3 or
V4
• S wave : First positive after R deflection
• R’ wave : Second positive deflection
• QRS could be monophasic or biphasic or triphasic ,
not every QRS contain Q ,R,S .

15. Q wave
• Any negative deflection that precedes an R
wave
• Q waves in different leads
• Small Q waves are normal in most leads ,
typically seen in the lateral leads
• Deeper Q waves (>2 mm) may be seen in
leads III and aVR as a normal variant
• Normally Q waves are not seen in V1-3
• Pathological Q Waves
• Usually indicate current or prior
myocardial infarction .
• Q waves are considered pathological
if:
• > 1 mm wide
• > 2 mm deep
• > 25% of depth of QRS complex
• Seen in leads V1-3

16. R wave
• Normally R wave progress from V1-V5
• Normal Transition in V3-4
• Poor R Wave Progression is defined by R
wave height ≤ 3 mm in V3

17. QRS complex comment should include :
• Duration: Normal < 2.5 small square , wide if > 3 small square
• Amplitude: normal/ low voltage/ alternans
• Axis : Normal axis or Abnormal (LAD,RAD,NW axis )
• Q wave : Detect any pathological Q waves
• R wave: Normal or Poor R progression

18. ST Segment
• Isoelectric line between the end of the S wave
(J point) and the beginning of the T wave
• Displacement: elevation/ depression
• Contour: horizontal /upsloping / downsloping

19. T wave
• Represent Ventricular repolarization
• Upright in all leads except aVR and V1
• Amplitude
< 1 large square in limb leads
< 2 large square in chest leads
• T wave abnormalities :
Peaked T waves , Hyperacute T waves ,
Inverted T waves , Biphasic T waves ,
Flattened T waves

20. T wave abnormalities
• Inverted: ischemia
• Peaked: Early ischemia, hyperkalemia (↑K)
• Flat/U waves: hypokalemia (↓K)

21. QT Interval
• Normal QT is 350-450 msec
• QT interval is less than half the
preceding RR interval
• QT interval should be adjusted for
heart rate (QTc)
• QTc is prolonged if > 450 ms
• QTc short if < 350 ms

22. Rate and Rhythm
• Normal heart rate : 60 – 100 beat per min
• Rate can be Normal /Tachycardia
/Bradycardia
• Rhythm can be Regular , regularly irregular ,
irregularly irregular
• How to calculate HR ?
• If the rhythm is regular :
• 300/RR interval in big squares.
• 1500/RR interval in small squares
• If the rhythm is irregular :
• Number of QRS complexes in 30 big square x
10.

23. Cardiac axis
• Normally the electrical activity begin at the SAN to
both atrium then spread to AVN down to His
bundle , right bundle and left bundle to Purkinje
fiber to cause ventricular depolarization.
• Whenever the direction of the electrical activity
move toward the lead cause positive deflection ,
move away the lead cause negative deflection ,
move parapedicular to the lead make biphasic
wave.
• Cardiac axis give us an idea of the overall direction
of electrical activity .

24. Normal Axis = QRS axis between -30° and +90°.
Left Axis Deviation = QRS axis between -30° and -90° .
Right Axis Deviation = QRS axis between +90° and
180.
Extreme Axis Deviation = QRS axis between -90° and
180° (AKA “Northwest Axis”).
Assessment for cardiac axis :
• look for lead I,III (or aVF ) and examine the QRS
complex in each lead and determine if it is Positive or
Negative
• Another method is by find Biphasic QRS and calculate
QRS axis , axis is 90 degree to biphasic lead .

30. How to write an ECG report
I. Rate
II. Rhythm
III. Waves
• P wave
• PR interval
• QRS complex ( Axis , width , amplitude , waves )
• ST segment
• T wave
• QT interval
IV : Final diagnosis

31. ECG Report
Rate : 300/3.5 = 85 beat per minute
Rhythm: Regular, normal sinus rhythm
waves :
• P wave: Normal P wave morphology and
axis , each P wave followed by QRS.
• PR interval : Normal , constant .
• QRS complex ( Axis , width , amplitude ,
waves ) : Normal
• T wave : Normal
• ST segment : Normal , isoelectric
• QT interval : Normal
Final diagnosis : Normal ECG

33. Common ECG abnormality
• Tachyarrhythmias
• Bradyarrhythmias
• Bundle branch blocks
• Myocardial ischemia and infarction
• Chamber Enlargement
• Miscellaneous

34. Tachyarrhythmias and Bradyarrhythmias
• The key for identification of the rhythm is the
identification of the pacemaker of the heart
• To be able to reach the final diagnosis you will
need to answer three questions : rate , rhythm,
and the pacemaker
• Normal pacemaker of the heart is SA node ,in
arrhythmia the pacemaker can be atrial focus ,
AVN or ventricular

35. Characteristic features of different types of pacemaker
• SA Node : P wave upright in lead I,II, inverted in aVR
• Normal sinus rhythm
• Sinus tachycardia
• Sinus bradycardia
• Sinus arrhythmia
• Sinus pause
• Atrial ectopic focus : P wave is small , inverted or replaced by fibrillatory or
flutter wave or there more than three P wave morphologies
• Atrial tachycardia
• Atrial flutter
• Atrial fibrillation
• Multifocal atrial tachycardia
• Wandering atrial pacemaker

36. • Junctional in AVN: P wave is absent or retrograde (negative in lead II , upright
in aVR , P wave just before or inside or after QRS)
• Junctional tachycardia
• Accelerated junctional rhythm
• Escape junctional Rhythm
• Ventricular ectopic focus : wide QRS complex , T wave axis opposite to QRS axis
and AV dissociation (no constant relation between P wave and QRS)
• Ventricular tachycardia
• Accelerated Ventricular rhythm
• Escape idioventricular rhythm
• Ventricular fibrillation

37. Sinus Rhythms
Regular narrow complex QRS with sinus
pacemaker (P wave upright in lead I,II,
inverted in aVR )
Heart rate :
• 60-100: Normal sinus rhythm
• >100 : Sinus tachycardia
• <60: Sinus bradycardia

38. • Sinus arrhythmia :changing sinus
node rate with respiratory cycle lead
to irregular sinus rhythm
• Sinus pause : SAN transiently ceases
to generate the electrical impulses ,
sinus pause lasting > 2-3 seconds is
called sinus arrest

39. Atrial Rhythms
Narrow complex QRS with atrial pacemaker , can be regular or
irregular according to type of arrhythmia
Regular
• Non sinus P-wave : Atrial tachycardia
• Flutter wave : Atrial flutter with fixed block
Irregular
• Fibrillatory wave : Atrial fibrillation
• Flutter wave : Atrial flutter with variable block
• 3 or more different P wave :
• Multifocal atrial tachycardia (rate > 100 )
• Wandering atrial pacemaker (rate < 100)

40. Atrial tachycardia
• Narrow QRS complex
• Tachycardia
• Regular
• Ectopic atrial focus : Non-sinus P wave ( small, Biphasic , inverted , .. )

42. Atrial fibrillation
• Narrow QRS complex
• Irregular ventricular response
• No P wave ( fine or coarse fibrillatory waves )
• Ventricular response can be normal , slow or rapid response

46. Atrial flutter
• Narrow QRS complex
• Flutter wave ( saw teeth appearance)
• Regular ventricular response , irregular if with variable AV block

49. Multifocal atrial tachycardia (MAT) ,
Wandering atrial pacemaker (WAP)
• Narrow QRS complex
• Irregular
• 3 or more different P wave
• Heart rate :
• <100 : Wandering atrial pacemaker
• > 100: Multifocal atrial tachycardia

50. Junctional Rhythms
Regular narrow complex QRS with
Junctional pacemaker (P wave come
just before or inside or after QRS)
Heart rate :
• > 100 : Junctional tachycardia
• 60-100 : Accelerated junctional rhythm
• 40-60 : Escape junctional Rhythm

51. SVT is any tachyarrhythmia arising from above the level of the Bundle of His,
It is often used synonymously with AV nodal re-entry tachycardia (AVNRT)
Classification of SVT :
Atrial :
Regular Atrial
• Sinus tachycardia
• Atrial tachycardia
• Atrial flutter
Irregular Atrial
• Atrial fibrillation
• Atrial flutter (variable block)
• Multifocal atrial tachycardia
AV node
• AVRT
• AVNRT
• junctional tachycardia

53. ECG features of AVNRT
• Regular tachycardia (150 -
200)
• Narrow QRS complexes
• P waves is absent , if visible
exhibit retrograde
conduction may be buried
within or after or before the
QRS complex

55. Ventricular Rhythms
Regular wide complex QRS ( > 120 ms )
with Ventricular pacemaker
• wide QRS complex
• T wave axis opposite to QRS axis
• AV dissociation (no constant relation
between P wave and QRS)
Heart rate :
• > 100 : Ventricular tachycardia
• 40-100 : Accelerated Ventricular rhythm
• <40 : Escape idioventricular rhythm

56. Ventricular tachycardia types:
• Monomorphic VT and Polymorphic VT
• Sustained VT and non-sustained VT

58. • Torsades de pointes (TdP) is a specific form of PVT occurring in the
context of QT prolongation , it has a characteristic morphology in
which the QRS complexes “twist” around the isoelectric line.
• Ventricular Fibrillation (VF) : Chaotic irregular deflections of varying
amplitude with no identifiable P waves, QRS complexes, or T waves.

60. Tachyarrhythmia
Narrow complex tachycardia
Regular
• Sinus tachycardia : P wave upright in lead I,II, inverted in aVR
• Atrial tachycardia ( focal ) : P wave is small or inverted
• Atrial flutter with fixed block : P wave is replaced by flutter wave
• Supraventricular tachycardia ( AVNRT ): P wave is absent or retrograde
• Junctional tachycardia : P wave is absent or retrograde
Irregular
• Atrial fibrillation : P wave is replaced by fibrillatory wave or absent P wave
• Atrial flutter with variable block : P wave is replaced by flutter wave
• Multifocal atrial tachycardia ( MAT ) : Three or more different P wave morphology

61. Wide complex tachycardia
Regular
• Ventricular tachycardia ( Monomorphic ) : Wide QRS complex , QRS are same morphology.
• Any regular SVT with aberrancy or preexcitation.
Irregular
• Ventricular tachycardia ( Polymorphic ) : Wide QRS complex with different morphology
• Ventricular fibrillation
• Any irregular SVT with aberrancy or preexcitation

62. Premature beats
• Premature Atrial Complex (PAC)
• Premature Junctional Complex (PJC)
• Premature Ventricular Complex (PVC)

63. Premature Atrial Complex (PAC)
• A premature beat arising from ectopic tissue within the atria. There is an
abnormal P wave, usually followed by a normal QRS complex.
• PACs may also be conducted aberrantly or not conducted at all.

64. Premature Junctional Complex (PJC)
• A premature beat arising from an ectopic focus within the Atrioventricular
(AV) junction.
• Narrow QRS complex, either without a preceding P wave or with a retrograde
P wave which may appear before, during, or after the QRS complex

65. Premature Ventricular Complex (PVC)
A premature beat arising from an ectopic focus within the ventricles.
Broad QRS complex with abnormal morphology
• Premature : occurs earlier than would be expected.
• Discordant ST segment and T wave changes.
• Usually followed by a full compensatory pause.
• Retrograde capture of the atria may or may not occur.

66. Heart block ( AV block)
• First degree HB
• Second degree HB ( Mobitz 1 , Mobitz 2 )
• Third degree HB ( Complete Heart block )

67. First degree HB
Prolonged PR interval > 5 small square

69. Mobitz I block (Wenckebach phenomenon)
Progressive PR lengthening followed by drop beat due to
malfunctioning AV nodal cells

70. Mobitz II block
intermittent non-conducted P waves without progressive
prolongation of the PR interval usually due to failure of
conduction at the level of the His-Purkinje system (i.e. below
the AV node)

71. Third degree heart block ( CHB )
• Severe bradycardia due to absence of AV conduction (Complete failure impulse conduct
from atrium to ventricle
• The ECG demonstrates bradycardia with complete AV dissociation (QRS rate < P rate)
• Regular P-P interval
• Regular R-R interval
• More P waves are present than QRS complexes ( AV dissociation )
• Bradycardia

72. Bundle branch block
•RBBB
•LBBB
•Hemiblock
•Bifascicular block
•Trifascicular block

73. RBBB
• Wide QRS > 120 ms (3 square)
• rSR’ pattern or broad monophasic R wave in V1-3
with 2ry T wave inversion
• Wide, slurred S wave in the lateral leads

75. LBBB
• Wide QRS > 120 ms (3 square)
• Dominant S wave in V1 (with ST and T
wave opposite QRS)
• Broad monophasic R wave in lateral leads

78. Intraventricular conduction delay
• Wide QRS but the pattern is not consistent with RBBB or LBBB .
• Can be due to fascicular block , Cardiomyopathy , LVH , Electrolyte abnormally , drugs as TCA
or Non-specific IVCD ( not due to any of the cause )

79. Hemiblock
Left anterior hemiblock (LAHB ,LAFB)
• Pathology in left anterior fascicle branch of left bundle
• ECG : LAD and deep S in inferior leads
Left posterior hemiblock (LPHB ,LPFB )
• Pathology in posterior fascicle branch of left bundle
• ECG : RAD and deep S in lateral leads

82. Bifascicular block
RBBB + LAHB or LPHB
Trifascicular block
Bifascicular block +
First degree AV block

85. Myocardial ischemia and infarction

86. ECG changes in myocardial ischemia
• Certain ECG findings suggest myocardial ischemia without total obstruction
• ECG findings should be in at least two successive leads in the same wall
• ECG changes :
• ST depression ≥ 0.5 mm
• T wave flattening / inversion

87. ECG changes in myocardial infarction (STEMI)
• ECG findings should be in at least two successive leads in the same wall
• ECG changes :
• ST elevation ( injury ) : ≥ 1mm in limb lead and ≥2mm in chest lead
• T wave changes ( Peripheral ischemia ) : Hyperacute T wave , Biphasic then
inverted
• Pathological Q (Central necrosis ) :Wide and deep Q wave
• Poor R progression
• Reciprocal ST depression : Presences STD in leads other than leads
showing STE , with inferior MI look for reciprocal in lateral leads , with
anterior MI looks for reciprocal STD in inferior leads

88. Stages of MI
 Hyperacute MI : Hyperacute T wave +- STE ( No pathological Q wave )
 Acute MI : STE , Pathological Q may present or not
 Recent MI ( subacute , evolving ) : Pathological Q wave , STD return to baseline , Inverted T wave
 Old MI ( chronic ) : Pathological Q or Poor R progression with Normal ST , T wave (Persistent STE in
old MI if with LV aneurysm )

93. Chamber Enlargement
• Left atrium enlargement
• Right atrium enlargement
• Left Ventricular Hypertrophy (LVH)
• Right Ventricular Hypertrophy (RVH)

94. LA enlargement :
Lead II : P mitrale, broad +- notched P wave
V1 : Negative deflection of P wave > 1*1mm
RA enlargement :
Lead II: P pulmonale ,Tall and peaked P wave
V1 : Positive deflection of P wave is tall > 1 mm

95. Left Ventricular Hypertrophy (LVH)
Voltage Criteria
• R wave in V5 or V6 > 25 mm ( 5 large square )
• R wave in V5 or V6 plus S wave in V1 or V2 > 35
mm (7 large square )
• R wave in aVL > 11 mm
Non Voltage Criteria (Strain pattern)
• ST depression +- T wave inversion in the lateral
leads
• ST elevation in V1-3
Additional ECG changes seen in LVH
• Left axis deviation
• IVCD

96. Typical appearance of LVH:
• S(V1 or V2) + R(V5 or V6) > 35mm
• Strain Pattern : ST Elevation V1-4 , ST Depression / Inverted T waves V5 and V6

97. Right Ventricular Hypertrophy (RVH)
• Dominant R wave in V1 (> 7mm tall or R/S ratio > 1)
• Dominant S wave in V5 or V6 (> 7mm deep or R/S ratio < 1)
• QRS duration < 120ms (changes not due to RBBB)
• Right axis deviation
• RV strain pattern : STD / T wave inversion in V1-4 and inferior leads.

98. Typical appearance of RVH:
• Dominant R wave in V1
• Dominant S wave in V6
• Right axis deviation
• Right ventricular strain pattern with ST depression and T-wave inversion in V1-4

100. Miscellaneous
• WPW syndrome
• Long QT syndrome
• Pericarditis
• Pacemaker ECG
• Low Voltage ECG
• Electrical alternans

101. Wolff-Parkinson-White (WPW) Syndrome
Presence of a congenital accessory pathway (AP)
that can result in symptomatic and life-
threatening arrhythmias.
ECG features of WPW :
• PR interval < 120ms
• Delta wave: slurring slow rise of initial
portion of the QRS
• Wide QRS

103. • QT interval usually measured in lead II or V5,V6 , however the
lead with longest measurement should be used
• QT interval is less than half the preceding RR interval
• QT interval is inversely proportional to heart rate , QT interval
shortens at faster rate and lengthens at slower rates so QT
interval should be corrected for heart rate ( corrected QT
interval , QTc )
• QTc estimated QT interval at standard heart rate of 60 bpm
Long QT syndrome

104. • Causes of a prolonged QTc :
• Congenital long QT syndrome
• Hypokalemia
• Hypomagnesaemia
• Hypocalcemia
• Myocardial ischemia
• Drugs
• Raised intracranial pressure
• QTc prolonged if > 440 ms in men , and > 460 ms in women
• Short QT if < 350ms

106. Pericarditis
• Widespread concave STE and PR depression
• Stages of ECG Findings in Pericarditis
Stage I - widespread ST elevation
Stage II - resolution of ST elevation, T wave flattening
Stage III - T wave inversion
Stage IV - resolution of T wave inversion

108. DD : Benign early repolarization (BER)
• usually benign ECG pattern producing widespread ST segment elevation that is commonly seen in young
• It is generally thought to be a normal variant that is not indicative of underlying cardiac disease
• Ecg : Widespread concave ST elevation , Notching or slurring at the J point

109. Pacemaker ECG
• Spike proceeding P wave or QRS or both

111. Low Voltage ECG
• Normal QRS amplitude : lead I + II + III > 15 small squares
• Low voltage criteria :QRS amplitude less than 5 mm in the limb leads and/or less than 10 mm
in the precordial leads.
• Causes of low voltage : Pleural effusion , Pericardial effusion, Emphysema, Obesity,
Myxedema , Infiltrative diseases as amyloid cardiomyopathy.

112. Electrical alternans
• Beat to beat variability in QRS voltage
• Due to massive pericardial effusion (swinging heart)

113. Massive pericardial effusion produces a characteristic ECG triad of:
• Low QRS voltage
• Tachycardia
• Electrical alternans

116. 1. The P wave represents_________.
2. The QRS complex represent_________.
3. The T wave represents__________.
4. The normal PR interval in adult is ________ ms.
5. In Normal Sinus rhythm the P wave negative in lead_____
and positive in lead _______.
6. A wide QRS with deep S wave in lead V1 and monophasic
R wave in V6 is seen in ______.
7. Tall and peaked P wave suggestive of _______.
8. Wide P wave ( >120 ms) in lead II suggest __________.
9. Normal QRS width is less than_____.

117. 10. Widespread STE with PR depression seen in______.
11. Lateral leads are lead________.
12. A premature beat with abnormal P wave followed with a normal
QRS complex is called __________.
13. Irregular narrow QRS complex with 3 or more different P wave and
normal heart rate is called _______.
14. Beat to beat variability in QRS voltage suggest________.
15. Progressive PR lengthening followed by drop beat seen in _______.
16. Normal QRS axis is between_______.

118. 17. A delta wave is seen in what syndrome ?
18. Name 3 causes that may prolong QT interval ?
19. Define Ventricular tachycardia ?
20. Define Atrial fibrillation ?
21. Name the LVH and RVH criteria ?
22. How to calculate heart rate in irregular rhythm ?
23. Name 3 causes of low voltage QRS complexes ?

131. ‘Work hard in
silence ,let
success make
the noise’