ECG by Dr.Sravani Vishnubhatla

DR. VISHNUBHATLA SRAVANI (PG)
MD (ANAESTHESIA)
MODERATOR: DR.OMKAR SIR
ECG
Dr.Sravani Vishnubhatla

ECG
➢ ECG is define as ‘’ recording of electrical activity of heart
on a graph paper.’’
Or
➢ Graphical representation of electrical activity of heart.

ECG leads.
➢ leads are electrodes which record the electrical potential of heart at
different sites.
➢ There are 12 ECG leads.
a) 3 bipolar limb leads.
b) 3 augmented limb leads.(unipolar).
c) 6 chest leads.

Bipolar limb leads.
➢ Lead 1 = left arm + ve , right arm -ve
➢ Lead 2 = right arm -ve ,left leg + ve..
➢ Lead 3 = left arm -ve , left leg +ve.

Augmented limb leads.
➢ A
VR
➢ AVL
➢ AVF
attach to right arm..
attach to left arm.
attach to left foot.

The limb electrodes
RA - On the right arm, avoiding thick muscle
LA – On the left arm this time.
RL - On the right leg, lateral calf muscle
LL- On the left leg this time.
The 6 chest electrodes
V1 - Fourth intercostal space, right sternal border.
V2 - Fourth intercostal space, left sternal border.
V3 - Midway between V2 and V4.
V4 - Fifth intercostal space, left midclavicular line.
V5 - Level with V4, left anterior axillary line.
V6 - Level with V4, left mid axillary line.
Electrodes
Usually consist of a conducting gel, embedded
in the middle of a self-adhesive pad onto
which cables clip. Ten electrodes are used for a
12-lead ECG.
Placement of electrodes

ECG PAPER
➢Recorded as a graph, with time represented
on x axis and voltage on y axis .
➢Divided into grid like boxes .
➢Each of small boxes is 1mm square .
➢Paper moves at a speed of 25 mm / sec
➢So horizontally each unit represents 0.04 sec.
➢1 mv = 10 mm in y axis , so each box is 0.1 mv
Every 5th line is highlighted and darker than
other lines , to define large box ,which consist
of 5 small squares vertically and horizontally .

❖P WAVE :denotes atrial depolarization
[electrical vector is directed from the SA node
towards the AV node].
❖QRS COMPLEX : denotes depolaization of
ventricle as well as repolarization of atrium.
❖T WAVE : denotes the repolarization [ or
recovery]of the ventricle.
The interval from the beginning of the QRS
complex to the apex of the T wave is referred
to as the ABSOLUTE REFRACTORY
PERIOD.
The last of the T WAVE is referred to as
the RELATIVE REFRACTORY PERIOD

P WAVE
➢1st positive deflection.
➢Activation of atria.
➢Normal width / duration : <2.5mm or 3 small squares .
➢+ve → L1 , L2 ,Avf & V2 – V6 .
➢-ve → Avr.
➢Can be Biphasic in V1 or V2 .

Abnormalities of P wave.
➢ P .pulmonale :- This is tall and peaked P wave in lead 1 and lead 2
and 3 in right atrial hypertrophy. (pulmonary
hypertension).
➢ P. mitrale ;_ It is biphasic or broad P wave seen in left atrial
hypertrophy.(mitral stenosis).
➢ -. Best seen in lead 2.

Q wave..
➢It is the 1st negative deflection .
➢Represents depolarization of Inter Ventricular Septum , by septal fascicle of
Lt bundle branch.
➢width : <1 mm (0.04 sec)
➢ht : ¼ of R wave in same lead .

Low voltage QRS complex.
when the height of R or S wave is not more than 5mm… it is seen
in..
➢ Hypothyroidism.
➢ Pericardial effusion.
➢ Thick chest wall.
➢ Problem in ECG machine.

High voltage QRS complex.
➢ This is present in ventricular hypertrophies.
➢ The maximum voltage of QRS complex may be 35 mv(35 small square).
➢ V1 and V2 show high voltage QRS complex in right ventricular
hypertrophy.( s wave)
➢ V5 and V6 show such QRS complex in left ventricular
hypertrophy. (r wave)

T wave
➢Represents ventricular repolarization .
➢Same direction as QRS complex .
➢ L2 → always + ve , aVR → always –ve , V4–6 →normally +ve .
➢V1-2 → can be +ve or –ve or isoelectric .

T wave.
➢ T wave should not be more than one third of R wave.
➢ T wave inversion represent ischemia of heart.
➢ Tall and peaked T wave is present in hyperkalemia.
➢ Flattened T waves in pericarditis and myocarditis.

U wave
➢Small round , upright wave followed by T wave .
➢In 20–30 % , it is seen .
➢Represents repolarization of purkinje fibers .
➢Also known as wave of late v.repolarization .
➢Mostly seen in slow HR .

J POINT
➢Also called as J junction .
➢Marks the end of QRS complex and beginning of ST segment .
➢J point , ST segment and T wave represents whole process of v.repolarization
➢V .repolarization starts at j point

INTERVALS AND SEGMENTS
➢SEGMENT IS A STRAIGHT LINE CONNECTING 2 WAVES .
➢INTERVAL CONSIST OF ATLEAST 1 WAVE PLUS THE CONNECTING
LINE .

PR segment:
➢Time taken by the AV node to conduct the impulse .
➢Straight line from end of p wave to start of qrs complex .
➢Measures the time from end of atrial depolarization to start of ventricle
depolarization .
PR interval:
➢Measured from beginning of p wave to beginning of qrs complex.
➢Measures the time from start of atrial depolarization to start of v.depolarization .
➢Normal → 3 – 5 mm (0.12 - .20 sec )

Prolong PR interval.
➢ Prolong PR interval shows delayed conduction from SA to AV node….
➢ In first degree heart , 2nd degree and complete heart block.
➢ Digitalis therapy.
➢ Hyperkalemia.

ST segment
➢Time gap btwn v.d & v.r .
➢No specific duration , but should be at same level as PR segment .
➢Starts from J point to beginning of T waves .
➢Represents the time when all cells are just depolarized and muscle cells are in
state at sustained contraction .

ST segment
➢ Elevation . Seen in recent MI and hyperkalemia.
➢ Depression. Seen in ischemia, digitalis therapy and hypokalemia.

Qt interval
➢Includes QRS complex , ST segment and T wave .
➢Measures the time from begining of v.depolarization to end of v.repolarization .
➢Represents total ventricular activity .
➢Normal → <0.42 sec in men & <0.44 sec in women .

Arrhythmias Classification
• The arrhythmias are categorizes into two major groups:
• 1.Bradycardias
• 2.Tachycardias.
The tachycardia group is then subdivided into narrow and wide
(broad) QRS complex variants, which are a major focus of ECG differential
diagnosis in acute care medicine and in referrals to cardiologists.

Bradycardias: Simplified Classification
➢Sinus bradycardia, including sinoatrial block
➢Atrioventricular (AV) junctional (nodal) and ectopic atrial escape
rhythms
➢AV heart block (second- or third-degree) or AV dissociation variants
➢Idioventricular escape rhythm (rule out hyperkalemia)

Major Tachyarrhythmias: Simplified
Classification
Narrow QRS
Complexes (NCT)
Wide QRS Complexes
(WCT)
Sinus tachycardia Ventricular tachycardia
(Paroxysmal)
supraventricular
tachycardias (PSVTs)*
Supraventricular tachycardia
with aberration/anomalous
conduction caused by:
(a) bundle branch block-type
pattern
(b) Wolff–Parkinson–White
preexcitation with (antegrade)
conduction down the bypass
tract
Atrial flutter
Atrial fibrillation

Rhythm Analysis
1.Rhythm
2.Rate
3.Axis
4.P wave
5.PR interval
6. QRS complex
7.T waves
8. QT interval
9.ST segment
10.other components

➢ Rhythm:
-regular
-irregular
1.irregularly irregular----AF
2.regularly irregular--sinus arrhythmia,2nd degree heart
block
➢Rate:
If rhythm is regular,
300/no.of big suares b/w 2 consecutive R waves
1500/small suares b/w 2 consecutive R waves
If rhythm is irregular,
no. of R waves in 6 seconds * 10

➢Axis
Right Returns
Left Leaves

Step 1: Determine regularity
➢Look at the R-R distances (using a caliper or markings on a pen or paper).
R R

Step 2: Calculate Rate
➢Option 1- Count the # of big squares between two R-R interval and divide
300 with that number.
300 / 3 = 100
➢Option 2 - Count the # of small squares between two R-R interval and
divide 1500 with that number.
1500 / 16 = 90

Step 3: Assess the P waves
➢Are there P waves?
➢Do the P waves all look alike?
➢Do the P waves occur at a regular rate?
➢Is there one P wave before each QRS?

Step 4: Determine PR interval
➢Normal: 0.12 - 0.20 seconds.
(3 - 5 small boxes)

Step 5: QRS duration
➢Normal: 0.04 - 0.12 seconds.
(1 - 3 small boxes)

Rhythm Summary
▪ Rate 90-95 bpm
▪ Regularity regular
▪ P waves normal
▪ PR interval 0.12 s
▪ QRS duration 0.08 s
▪ Interpretation?
Normal Sinus Rhythm

Normal Sinus Rhythm (NSR)
➢Etiology: the electrical impulse is formed in the SA node and
conducted normally.
➢This is the normal rhythm of the heart; other rhythms that do not
conduct via the typical pathway are called arrhythmias.

NSR Parameters
▪ Rate 60 - 100 bpm
▪ Regularity regular
▪ P waves normal
▪ PR interval 0.12 - 0.20s
▪ QRS duration 0.08 - 0.12s
▪ QT Interval 0.4 – 0.42s
▪ ST segment 0.08s
▪ T Wave 0.2s

Arrhythmia Formation
Arrhythmias can arise from problems in the:
➢Sinus node
➢Atrial cells
➢AV junction
➢Ventricular cells

SA Node Problems
The SA Node can:
➢fire too slow
➢fire too fast
Sinus Bradycardia
Sinus Tachycardia

Atrial Cell Problems
Atrial cells can:
➢fire occasionally from a focus
➢fire continuously due to a
looping re-entrant circuit
Premature Atrial Contractions (PACs)
Atrial Flutter
Atrial fibrillation

AV Junctional Problems
The AV junction can:
➢ block impulses coming from
the SA Node
Paroxysmal Supraventricular
Tachycardia
AV Junctional Blocks

Ventricular Cell Problems
Ventricular cells can:
➢fire occasionally from 1 or more
foci
➢fire continuously from multiple
foci
Premature Ventricular Contractions
(PVCs)
Ventricular Fibrillation
Ventricular Tachycardia

Rhythm #1
➢ Rate? 30bpm
➢ Regularity? regular
➢ P waves? normal
➢ PR interval? 0.12s
➢ QRS duration? 0.10s
➢ Interpretation? Sinus Bradycardia

Rhythm #2
➢ Rate? 130bpm
➢ P waves? normal
➢ Interpretation? Sinus Tachycardia

Remember …
• When an impulse originates anywhere in the atria (SA node, atrial
cells, AV node, Bundle of His) and then is conducted normally
through the ventricles, the QRS will be narrow (0.04 - 0.12 s).

Rhythm #3
➢ Rate? 140bpm
➢ Regularity? Irregularly regular
➢ P waves? none
➢ PR interval? none
➢ Interpretation? Atrial Fibrillation

Rhythm #4
➢ Rate? 250bpm
➢ P waves? flutter waves
➢ Interpretation? Atrial Flutter

➢Atrial flutter

Rhythm #5

Rhythm #6
➢ Rate? 160bpm
➢ P waves? none
➢ QRS duration? wide (> 0.12s)
➢ Interpretation? Ventricular Tachycardia

Rhythm #7
➢ Rate? none
➢ Regularity? irregularly regular
➢ P waves? none
➢ QRS duration? Wide, if recognizable
➢ Interpretation? Ventricular Fibrillation

➢Torsades de pointes

Rhythm #8
➢ Rate? 60bpm
➢ P waves? normal
➢ Interpretation? 1st Degree AV Block

Rhythm #9
➢ Rate? 50bpm
➢ Regularity? Regularly irregular
➢ P waves? nl, but 4th no QRS
➢ PR interval? lengthens
➢ Interpretation? 2nd Degree AV Block, Type I

2nd Degree AV Block, Type I
➢Etiology: Each successive atrial impulse encounters a longer and
longer delay in the AV node until one impulse (usually the 3rd or
4th) fails to make it through the AV node. It is otherwise called
“Wenckebach phenomenon”

Rhythm #10
➢ Rate? 40bpm
➢ P waves? nl, 2 of 3 no QRS
➢ Interpretation? 2nd Degree AV Block, Type II

Rhythm #11
Rate? 40bpm
Regularity? regular
P waves? no relation to QRS
PR interval? none
QRS duration? Wide (> 0.12s)
Interpretation? 3rd Degree AV Block

3rd Degree AV Block
➢Etiology: There is complete block of conduction in the AV junction,
so the atria and ventricles form impulses independently of each other.
Without impulses from the atria, the ventricles own intrinsic
pacemaker kicks in at around 30 - 45 beats/minute.

PR-INTERVAL
Wolff–Parkinson–White syndrome
Wolf Parkinson White Syndrome One
beat from a rhythm strip in V2
demonstrating characteristic findings in
WPW syndrome. Note the characteristic
delta wave (above the blue bar), the short
PR interval (red bar) of 0.08 seconds, and
the long QRS complex (green) at 0.12
seconds
Accessory pathway (Bundle of Kent)
allows early activation of the ventricle
(delta wave and short PR interval)

ECTOPICS
Pre mature atrial contraction
Pre mature Ventricular contraction

VENTRICULAR BIGEMINY:
Every other beat is a PVC.
Treatment:
▪ Beta Blockers
▪ Calcium channel Blockers
▪ Anti Arrhythmics
▪ Cardiac Ablation in severe cases who cannot take medication
▪ Cessation of smoking, alcohol and Caffeine

VENTRICULAR TRIGEMINY:
Every third beat is a PVC.
Treatment:
▪ Beta Blockers
▪ Calcium channel Blockers
▪ Anti Arrhythmics
▪ Cardiac Ablation in severe cases who cannot take medication
▪ Cessation of smoking, alcohol and Caffeine

Bundle Branch Blocks
With Bundle Branch Blocks you will see two changes on the ECG.
1. QRS complex widens (> 0.12 sec).
2. QRS morphology changes (varies depending on ECG lead, and if
it is a right vs. left bundle branch block).

Bundle Branch Blocks
Why does the QRS complex widen?
When the conduction pathway is blocked it will
take longer for the electrical signal to pass
throughout the ventricles.

Right Bundle Branch Blocks
What QRS morphology is characteristic?
V1
For RBBB the wide QRS complex assumes a unique, virtually
diagnostic shape in those leads overlying the right ventricle (V1 and V2).
“Rabbit Ears”

MARROW
V1 V6

Left Bundle Branch Blocks
What QRS morphology is characteristic?
For LBBB the wide QRS complex assumes a characteristic change in shape
in those leads the left ventricle (right ventricular leads - V1 and V2).
Broad,
deep S waves
Normal

WILLIAM
V1 V6

LVH VS RVH
LVH
➢Deepest s wave in v1 or v2
+
➢Tallest R wave v5 or v6
➢If total >35mm, then it is
LVH
RVH
➢Right ax is deviation
➢R/S >1 in V1
<1 IN V5 V6
➢R wave in v1 >7mm

LEFT ANTERIOR FASCICULAR BLOCK/
HEMIBLOCK
ON ECG:
LAD( usually -45 to-90)
qR complexes in lead 1, avL
rS complexes in lead 2 3 avF
PROLONGED R wave
peak time in avL> 45ms

REFERENCES
➢BASIC AND BEDSIDE ELECTROCARDIIOGRAPHY BY
ROMULO.F.BALTAZAR.
➢ECG MADE WASY BY JOHN R HAMPTON

ECG by Dr.Sravani Vishnubhatla

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