The document provides an overview of electrocardiogram (ECG or EKG) interpretation. It discusses cardiac anatomy and physiology relevant to understanding ECGs. The basics of the 12-lead ECG system are explained, including the six limb leads and six precordial leads. Components of the ECG waveform like the P, QRS, and T waves are defined. An 8-step method for ECG interpretation is outlined, beginning with analyzing the rhythm and rate, and then evaluating each waveform and interval. Key points include determining normal durations for the P wave, PR interval, QRS complex, QT interval, and identifying abnormalities. The summary restates normal findings for a sinus rhythm ECG.

1. THE BASICS OF ECG INTERPRETATION
Dr. Anil Sharma, PhD(N)
Principal, Manikaka
Topawala Institute of
Nursing-CHARUSAT,
Changa
Accredited Grade “A” with
NAAC
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2. Flow of Presentation
 Quick Recapping of Cardiac Anatomy &
Physiology.
 Learning 12 Lead ECG and understanding
rhythm strips
 Understanding interpretation of ECG in
terms of:
 Significance and variation
 Calculating rate and rhythm
 Step-by-step approach for interpretation
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3. • Heart Chambers
• Heart valves
• Blood flow
• Cardiac cycle dynamics (cardiac output, stroke
volume, preload, afterload, contractility)
• Conduction system (SA, AV node, bundle of His,
bundle branches, Purkinje fibers)
• Innervation of the Heart (ANS-Sympathetic &
Parasympathetic)
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Cardiac Anatomy & Physiology

4. ECG (ElectroCardioGram/ElectroCardioGraphy):
Graphical record of electrical potentials produced
during heartbeat.
Or
Graphical representation of heart’s electrical activity
in waveforms
Process:
Heart electrical activity Produce Currents
Radiate to skin via surrounding tissues
The electrodes sense these current and transmit as
ECG 4

5. • Current then transformed into waveform &
represent the heart’s depolarization and
repolarization cycle.
• ECG shows precise sequence of electrical
events occurring in each cardiac cycle.
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6. Pre-requisite to interpret ECG:
• Leads & Planes: During ECG recording the
waveforms which carries information of current
from different perspectives, that known as leads
and Plans.
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7. • Lead: it provide a view of the heart’s electrical
activity between one positive and one negative
pole.
• Between the two poles a imaginary line
represent the lead axis (Direction of the
current movement)
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9. Plane: It reflect cross-sectional perspective of the
heart’s electrical activity.
 Frontal Plane:
 Horizontal plane:
• Frontal Plane: Six limb leads (I, II, III, aVR, aVL, and
aVF)
• Horizontal plane: Six Chest leads (V1 to V6) 9

10. 12-Lead ECG
• It give 12 different views of the heart.
• These views obtained through electrodes which placed at
limb and chest.
1. Six Limb Leads: Lead I, II & III are Bipolar (require –ve
and +ve electrode for monitoring) and Augmented vector
Right (aVR), Augmented vector Left (aVL ), Augmented vector
Foot (aVF) are Unipolar as information collect from one lead
2. Six Precordial or V leads: These are Unipolar leads
known as V1,V2,V3,V4,V5 & V6.
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Lead Characteristic
I Reflect current moving right to left (-ve to +ve): positive
deflection (Arterial rhythms)
II +ve electrode on left leg and –ve on right arm: positive
deflection (Sinus Node)
III +ve electrode on left leg and –ve on left arm: positive
deflection

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Lead Characteristic
aVR
+ve electrode on right arm and produce negative deflection
(current moves away from the lead)
aVL
+ve electrode on left arm and produce positive deflection
aVF
+ve electrode on left leg and positive deflection

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Lead Characteristic
V1 Placed right side of sternum at 4th intercostal rib space
V2 Placed at left of the sternum at the 4th intercostal rib space
V3 Placed between V2 & V4
V4 Placed at 5th intercostal space at midclavicular line
V5 Placed at 5th intercostal space at anterior axillary line
(produce positive deflection)
V6 Placed with level of V4 at the midaxillary line.
(produce positive deflection)

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16. Lead representation of heart
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I
Lateral
aVR
V1
Septal
V4
Anterior
II
Inferior
aVL
Lateral
V2
Septal
V5
Lateral
III
Inferior
aVF
Inferior
V3
Anterior
V6
Lateral

17. ECG Strip
• It is a piece of paper used to record ECG.
• ECG paper consist of horizontal and vertical
lines forming a grid.
• Horizontal axis represent time.
• Small block-0.04 second
• 5 small block create one large block-.2 second
• 5 large block- 1 second
• Vertical axis represent amplitude in millimeters
(mm) or electrical voltage in millivolts (mV).
• Small block-1 mm or 0.1 mV
• Large block- 5 mm or 0.5 mV
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18. Interpreting A Rhythm Strip
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P wave:
represent arterial depolarization.
• Location- Precedes the QRS complex
• Amplitude- 2 to 3 mm high
• Duration- 0.06 to 0.12 second
• Configuration-usually rounded and upright
• Positive deflection in leads I, II, aVF and V2 to V6
but variable in lead III & aVL & V1. Also negative
or inverted in lead aVR

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PR Interval:
It track atrial impulse from atria via AV node, bundle of
His and right & left bundle branches.
(Amplitude, Configuration and Deflection aren’t
measured)
• Location- Beginning of P wave to beginning of QRS
complex
• Duration- 0.12 to 0.20 second

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QRS Complex:
represent ventricles depolarization.
• Location- follows the PR interval
• Amplitude- 5 to 30 mm high but differ for each lead
• Duration- 0.06 to 0.10 second (Half of PR interval)
• Configuration- Q wave- First negative deflection,
• R wave- First Positive deflection after p wave
• S wave- First negative deflection after R wave
• Positive deflection in leads I, II, III, aVL, aVF and
V4 to V6 and negative in lead aVR & V1 to V3

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ST Segment:
represent end of ventricles depolarization and the
beginning of ventricles repolarization.
(Amplitude, Duration and Configuration aren’t
measured)
• Location- extend from the S wave to the beginning of
T wave
• Deflection- Isoelectric (neither positive nor
negative)
• Vary from -0.5 to +1 mm in some chest leads

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T wave:
represent ventricles repolarization.
(Duration isn’t measured)
• Location- Follows the S wave
• Amplitude- 0.5 mm in leads I, II & III (10 mm in
Chest leads)
• Configuration- typically rounded and smooth
• Positive deflection in leads I, II and V3 to V6 but
negative or inverted in lead aVR
• variable in other lead

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QT Interval:
It measures ventricular depolarization and repolarization.
Length of QT interval varies as per Heart Rate
(inversely proportional)
(Amplitude, Configuration and Deflection aren’t observed)
• Location- Beginning of QRS complex to end of T wave
• Duration- Varies as per age, gender & Heart Rate.
generally 0.36 to 0.44 second

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U wave:
represent the recovery period of Purkinje or ventricular
conduction fibers.
(It may or may not be present of ECG Strip)
(Amplitude & Duration aren’t measured)
• Location- Follows the T wave
• Configuration- typically upright & rounded
• Deflection- Upright

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8-Step Method of Interpretation
• Determining the Rhythm
• Determining the Rate
• Evaluate the P wave
• Determine the Duration of PR interval
• Determine the Duration of the QRS complex
• Evaluate the T Wave
• Determine the Duration of the QT interval
• Evaluate any other component

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Step-1: Determining the Rhythm
• Use paper pencil method
• For atrial rhythm measure P-P interval (If regular
then interpret it as regular atrial rhythm)
• For ventricular rhythm measure R-R interval (If
regular then interpret it as regular ventricular
rhythm)

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Step-2: Determining the Rate
• 10-times method – consider as easiest method
(Especially when rhythm is irregular)
• To obtain Ventricular rate- count the number of R
waves that appear within 10 second period and
multiply by 6.
• Ten 6-second strip will represent one minute
• Atrial rate can be identified by using P wave

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Step-3: Evaluate the P wave
Can we interpret by answering following points:
• Presence of P wave.
• Match it with normal configuration.
• Do all have similar size and shape?
• Is these each QRS complex has one P wave or not?

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Step-4: Determine the Duration of PR interval
First Measure it by counting small squares between
the start of P wave and start of QRS complex and
then multiply the number of squares by 0.04 seconds
Example: 5 small squares fall then multiply it with
0.04 (5×.04= .20 second)
Can we interpret by answering following points:
• Is the duration of it is 0.12 to 0.20 Second ?
• Is it constant ?

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Step-5: Determine the Duration of the QRS complex
First Measure it by counting small squares between
Beginning and end of QRS complex and multiply the
number of squares by 0.04 seconds
Example: 3 small squares fall then multiply it with
0.04 (3×.04= .12 second)
Can we interpret by answering following points:
• Is the duration is normal 0.06 to 0.10 Second ?
• Are all QRS complexes the same size and shape ?
• Does it appear after every P wave ?

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Step-6: Evaluate the T Wave
Can we interpret by answering following points:
• Presence of T wave
• Do all T wave are in normal shape?
• Do they all have normal and same amplitude?

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Step-7: Determine the Duration of the QT interval
First Measure it by counting small squares between
Beginning of QRS complex and the end of T wave and
multiply the number of squares by 0.04 seconds
Example: 10 small squares fall then multiply it with
0.04 (10×.04= .40 second)
Can we interpret by answering following points:
• Is the duration is normal 0.36 to 0.44 Second ?
• Are all QRS complexes the same size and shape ?
• Does it appear after every P wave ?

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Step-8: Evaluate any other component
we can evaluate other parameters by noting ECG strip,
such as:
• Presence of U wave
• Origin of the rhythm
• Rate characteristic
• Rhythm abnormalities

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Summery of Interpretation of Normal sinus
rhythm
• Atrial and ventricular rhythms are regular
• Atrial and ventricular rate range between 60 to 100 beats per
minute
• P wave rounded, smooth and upright in Lead II (reflect the
impulse reached to atria)
• Normal PR interval (0.12 to 0.20 sec.) (reflect the impulse
following regular conduction pathway)
• Normal QRS duration (< 0.12 sec.) (reflect normal ventricular
depolarization and repolarization)
• T wave upright in Lead II (Reflecting that normal repolarization
took place)
• Normal QT interval (0.36 to 0.44 sec.)
• No aberrant or ectopic beats presence.

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Selected References:
• Coviello, Jessica Shank (2016). ECG Interpretation Made Incredibly Easy
(6rd Ed.). Lippincott Williams & Wilkins
• Patricia A. Potter, A. Stockert et al (2014). Fundamentals of nursing (2nd
ed.). South Asian edition. Elsevier.
• Janice L.N., & Kerry H.C. (2014). Textbook of Medical-surgical nursing
volume-1 (13th ed.). South Asian Edition: Wolters Kluwer Health
• Weber J. & Kelley,J. (2010) health assessment in nursing (4th ed.).
Lippincott Williams & Wilkins

38. Thank You
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