Ecg basics and interpretation

ECG: Basics and Interpretation

Contents
 Basics of Electrocardiogram (ECG)
 Interpreting ECGs
 Common Cardiac Problems
 Troubleshooting ECG Problems
 Summary
 Abnormal Heart Rhythms

Objectives
By the end of this presentation, you will be familiar with:
 Conduction system of the heart
 Basic procedure of ECG
 Interpreting normal ECGs and ECG abnormalities
 Identifying common errors in ECG and troubleshooting them

Basics of Electrocardiogram (ECG)

• It aids in the diagnosis and treatment of various cardiac and other related
disorders.2
What is an ECG?
• An ECG is a diagnostic tool that records the electrical activity of the
heart.1
1. Ashley EA, Niebauer J. Cardiology Explained. London: Remedica, 2004.
2. Booth KA, DeiTos P, O’Brien TE. Electrocardiography for Healthcare Personnel, 2nd edn. Boston: McGraw-Hill Higher Education, 2008.

History
AlGhatrif M, Lindsay J. A brief review: History to understand fundamentals of electrocardiography. JCHIMP 2012;2(1):1-5.
1842 1887 1893 1901 1924 1934 –1938 1942 1954
Matteucci
recorded
electrical
activity
from the
heart of a
frog
Waller recorded
first electrical
activity from
human heart
Einthoven
first used the
term EKG
Einthoven
built string
galvanometer
-based 3-lead
EKG machine
Wilson invented
the central
terminal.
Precordial leads
were born.
AHA
standardized
12-lead as we
know it now
Einthoven
won Nobel
Prize
Goldberg used the
central terminal with
augmentation.
Augmented unipolar
leads were born.

Cardiac Conduction System
ECG Interpretation made Incredibly Easy, 5th edn. Philadelphia: WoltersKluwer Health Lippincott Williams and Wilkins, 2011.
SA node
 60100 per min
AV junction
 4060 per min
Purkinje fibers
 2040 per min

Types of ECGs
• Two types: 12-lead ECG and Rhythm strip
MCL: Modified chest lead
• Advanced ECG or EASI system enables continuous 12-lead ECG
monitoring using only five electrodes
• Rhythm strip provides information from one or more leads
simultaneously
• 12-lead ECG records information from 12 different views and requires
placement of 12 leads on patients’ limb and chest

ECG Leads
ECG Interpretation made Incredibly Easy, 5th edn. Philadelphia: Wolters Kluwer Health Lippincott Williams and Wilkins, 2011.
Einthoven’s triangle
• The leads include:
 standard limb leads,
 augmented limb leads,
 chest leads and
 modified chest leads
• Standard limb leads: I, II and III
• The electrode placement is
referred to as Einthoven’s
triangle

Augmented Limb Leads
• Augmented limb leads are unipolar
leads and include aVR, aVL and aVF.
• The letter ‘a’ stands for ‘augmented’
and letters R, L, and F stand for
positive electrode position of the lead.
• They measure electrical activity
between one limb and a single
electrode.
• While aVR provides no specific view,
aVL and aVF show electrical activity
from lateral and inferior wall of the
heart, respectively.
• aVR produces negative deflection and
aVL and aVF produce positive
deflections.

Lead V1 V2 V3 V4 V5 V6
Positive
Electrode
Placement
4th
intercostal
space on
right side
of sternum
4th
intercostal
space on
left side of
sternum
Midway
between
V2 and
V4
5th
intercostal
space at the
midclavicular
line on the
left
Midway
between
V4 and V6
level with
V4
Midaxillary
line on
left, level
with V4
View of
Heart
Surface
Septum Septum Anterior Anterior Lateral Lateral
Chest or Precordial Leads
• Chest or Precordial leads are unipolar leads and provide ECG
view in horizontal plane.
• Include V1, V2, V3, V4, V5,V6
Jenkins P. Nurse to Nurse ECG Interpretation. London: McGraw-Hill Education, 2009.
Chest Leads

Precordial Leads: Different Views

Precordial Leads: Uses
• Lead V5 shows changes in the ST segment or T wave.
• Lead V3 can be used to detect ST-segment elevation.
• It is also useful in monitoring ventricular arrhythmias, ST-segment
changes and bundle branch blocks.
• The lead V1 helps to differentiate between right and left
ventricular ectopic beats that occur due to myocardial irritation or
other cardiac stimulation.

12-Lead Electrode Placement

Modified Chest Leads
• Modified chest lead 1 (MCL)1 is similar to lead V1 created by placing the
negative electrode on the left upper chest, positive electrode on the right
side of the sternum at the 4th intercostal space and the ground electrode
on the right upper chest below the clavicle.
• Modified chest lead (MCL)1 can be used to assess bundle branch
defects.
• It is used to monitor premature ventricular contractions, and
distinguish between different types of tachycardia.
• Modified chest lead (MCL)6 may be used as an alternative to MCL1.
• Bipolar leads MCL1 and MCL6 along with I, II, III, V1 and V6 are the
commonly monitored leads.
MCL:Modified chest lead

Lead Placement in Special Cases: Limb Amputation
• In case of arm or leg amputations, respective limb electrodes are
placed as far distally as possible.1
1. Crawford J, Doherty L. Practical Aspects of ECG Recording. Cumbria: M&K Update Ltd, 2012.
2. ECG Training Module. Rajasthan Medical Services Corporation. Government of Rajasthan. Available at:
http://www.rmsc.nic.in/pdf/Training%20Module%20-%20ECG.pdf. Accessed on: 06 October 2014.
• Both leg leads can be placed on left leg as long as the left lead is
higher up the leg than the right leg lead.2
• The precordial electrodes remain on the correct anatomical
positions.1
• The limb leads should not be placed on torso.1
• The deviation is documented on ECG.1

Burns and Skin Conditions
• Leads should not be placed on parts where the integrity of the skin
is compromised.
Crawford J, Doherty L. Practical Aspects of ECG Recording. Cumbria: M&K Update Ltd, 2012.
• Greasy medications on damaged skin may cause wandering
baseline artifacts.
• In extensive burns and severe skin conditions, it is better to rely on
suboptimal tracings till the skin heals.
• Careful skin preparation should be done before placement.
• Proper infection control measures should be employed before
placing the electrodes.

• When serial ECGs are required, the chest can be marked to keep
electrode placement constant.
Pediatric Patients
• Locating anatomical positions especially in premature babies may
be difficult.
• Additional leads include V3R, V4R and V7.
• In addition to standard electrodes, additional electrodes can be
applied routinely.
• Very little pressure should be applied while locating the intercostal
spaces.

Pediatric Patients: Additional Leads
• V7 is located on the left side on the
horizontal levels of V4, V5 and V6 on the
posterior axillary line and is attached to
V3 lead.
• V3R is placed midway between V4R
and V1 and is attached to the V2
lead.
• V4R is placed first on the 5th
intercostal space on the right
midclavicular line and is attached to
the V1 lead.
• Additional leads provide information
on congenital structural
abnormalities.

ECG Waveforms
1. ECG Interpretation made Incredibly Easy, 5th edn. Philadelphia: WoltersKluwer Health Lippincott Williams and Wilkins, 2011.
2. Bowbrick S, Borg AN. ECG Complete. Philadelphia: Elsevier, 2006.

ECG Waveforms
What do the waves mean?1
Deflection What it represents
P wave Atrial depolarisation
PR interval Time delay between atrial depolarisation and ventricular activation
QRS
complex
Ventricular depolarisation
ST segment
(isoelectric)
Electrical plateau of ventricular activation
T wave Ventricular repolarisation
QT interval Total time for ventricular depolarisation and repolarisation
U wave Possibly septal or late ventricular repolarisation
Bowbrick S, Borg AN. ECG Complete. Philadelphia: Elsevier, 2006.

The P Wave
• Represents atrial depolarization (conduction of electrical impulse
through the atria)
• Location: Precedes the QRS complex
• Amplitude: 23 mm high
• Duration: 0.060.12 seconds
• Configuration: Usually rounded
and upright
• Deflection: Positive in leads I, II, aVF,
and V2 to V6, negative in lead aVR;
variable in other leads

Abnormal P Wave
• Peaked, notched or enlarged P: Atrial hypertrophy or enlargement
associated with COPD, pulmonary emboli, valvular disease or heart
failure
• Inverted P waves: Retrograde conduction from the AV junction
towards atria
• Varying P waves: Impulse may be coming from different sites such
as wandering pacemaker rhythm, irritable atrial tissue, damage
near the SA node
• Absent P waves: Conduction by a route other than the SA node
(junctional or atrial fibrillation rhythm)
COPD: chronic obstructive pulmonary disease; AV: atrioventricular; SA: sinoatrial

The PR Interval
• The PR interval represents atrial impulse from the atria through
AV node, bundle of His and right and left bundle branches.
AV: atrioventricular
• Duration: 0.120.20 seconds
• Location: From the beginning of the P wave to the beginning of
the QRS complex

Abnormal PR Interval
• Short PR intervals of <0.12 seconds: Impulse has originated
somewhere other than the SA node as seen in junctional
arrhythmias and pre-excitation syndromes
• Prolonged PR intervals of >0.20 seconds: Conduction delay
through the atria or AV junction as seen in digoxin toxicity or heart
block
AV: atrioventricular; SA: sinoatrial

The QRS Complex
• QRS complex represents ventricular depolarization
• Location: Follows the PR interval
• Amplitude: 530 mm high; differs as per lead used
• Duration: 0.060.10 seconds, or half of PR interval
• Configuration: Consists of Q (negative), R (positive)
and S (negative) waves
• Deflection: Positive in leads I, II, III, aVL, aVF, and V4
to V6 and negative in leads aVR and V1 to V3

Abnormal QRS Complex
• Interpreting QRS complex is crucial as it represents intraventricular
conduction time.
• Deep, wide Q waves: Myocardial infarction; amplitude of Q wave
25% of the R wave or duration of Q wave is 0.04 seconds or more
• Notched R wave: Bundle branch block
• Widened QRS (>0.12 seconds): Ventricular conduction delay
• Missing QRS: AV block or ventricular standstill
• If P wave does not appear with the QRS complex: Ventricular
arrhythmia
AV: atrioventricular

The ST Segment
• The ST segment represents the end of ventricular depolarization
and beginning of ventricular repolarization
• J point: Point that marks the end of the QRS complex and
beginning of the ST segment
• Location: Extends from the S wave to the beginning of the T wave
• Deflection: Isoelectric; may vary from –0.5 to +1 mm in some
precordial leads

Abnormal ST Segment
• Myocardial ischemia
• Digoxin toxicity
• Myocardial injury
0.5 mm or more below
the baseline
1 mm or more above
the baseline

The T Wave
• T wave represents ventricular recovery or repolarization
• Location: Follows the S wave
• Amplitude: 0.5 mm in leads I, II and III and up to 10 mm in
precordial leads
• Configuration: Round and smooth
• Deflection: Upright in leads I, II and V3to V6; inverted in lead aVR;
variable in other leads

Abnormal T Wave
• Tall, peaked or tented T wave: Myocardial injury or hyperkalemia
• Inverted T waves in leads I, II, or V3 through V6: Myocardial
ischemia
• Heavily notched or pointed T waves in adults: Pericarditis

• QT interval determines ventricular depolarization and
repolarization
• Location: Extends from the beginning of the QRS complex to the
end of the T wave
• Duration: 0.360.44 seconds; varies according to age, sex, and
heart rate
The QT Interval
• Length varies according to the heart
rate. Faster the heart rate, shorter
is the QT interval.
• When the rhythm is regular, duration
of QT interval should not be greater
than half the distance between
consecutive R waves.

Abnormal QT Interval
• Abnormality in duration of QT interval indicates myocardial
problems
• Prolonged QT: Increases the risk of a life-threatening arrhythmia
known as torsades de pointes
• Certain medications also increase the QT interval such as
amiodarone, amitriptyline, chlorpromazine
• Prolonged QT may also indicate congenital conduction system
defect present in certain families
• Short QT interval: Digoxin toxicity or hypercalcemia

• The U wave may not appear in all rhythm strips.
The U Wave
• Prominent U wave indicates
hypercalcemia, hypokalemia or
digoxin toxicity
• Configuration: Typically upright
and rounded
• Location: Follows the T wave
• If present, it represents the recovery period of the Purkinje or
ventricular conduction fibers

Interpreting ECG: The 5-Step Approach
Evaluate duration of QRS interval
Evaluate duration of PR interval
Evaluate P wave
Determine rhythm
Determine rate

ECG Grid

Rate
Rule of 300
• Identify the QRS complex
• Count the number of large boxes between one QRS wave and the
next one
• Divide 300 by this number
• The resultant number is the heart rate
No. of large squares between QRS complexes Heart rate (bpm)
5 60
4 75
3 100
2 150
Ashley EA, Niebauer J. Cardiology Explained. London: Remedica, 2004.

Rule of 300: An Example
• Number of large boxes between one QRS wave and the next one is 6
• 300/6=50 beats per minute

10-Second Rule
• This is particularly useful when the rhythm is
irregular
• Obtain a 6-second strip
• Count the number of P waves in the strip
• Multiply the number by 10 to get the number of
atrial beats per minute
• Repeat the same for ventricular rate by counting
the number of R waves and multiplying by 10

10-Second Rule: Example
• Number of R waves in the 6-second strip: 7
• Ventricular heart rate—710=70 beats per minute

Rhythm
• Atrial rhythms are
evaluated by measuring
intervals between
consecutive P waves
• Ventricular rhythms are
evaluated by measuring
intervals between
consecutive R waves
• In the absence of R waves,
use the Q wave
• Paper-and-pencil method
or the caliper method can
be used for measuring the
rhythms.
Paper-and-
pencil
method
Caliper method

Evaluating P Wave
P wave checklist
• Check if P waves are present
• Check if they all have normal configurations
• Check if they all have similar size and shape
• Check if there is a P wave for every QRS complex
Normal P wave characteristics
• Upright
• Uniform
• Round
• One-to-one
• Ratio with QRS complex

• To determine the PR interval, count the small squares between
start of the P wave and the start of the QRS complex
• Then, multiply the number of squares with 0.04 sec
• If the resultant duration is between 0.12 and 0.20 sec, it is
considered to be normal
• Check if the PR interval is constant
Evaluating Duration of PR Interval

• To determine QRS complex, count the small squares between start
and the end of the QRS complex
• Measure from the end of the PR interval to the end of the S wave
and not just the peak
• Multiply the number by 0.04 sec
• If the resultant duration is between 0.06 and 0.10 sec, it is
considered to be normal
• Check if all QRS complexes are of same size and shape
• Check if QRS complex appears after every P wave
Evaluating Duration of QRS Complex

Additional Observations
Additional observations are useful to interpret electrolytes, medications and
myocardial damage.1 They include:
• T wave: Presence, shape and amplitude (if all the T waves have same
amplitude and deflection)
• Duration of QT interval: Count the number of small squares between the
beginning of the QRS complex and the end of the T wave and multiply this
number by 0.04 sec (normal range is 0.360.44 sec)
• Other components: Check for ectopic beats and other abnormalities, ST
segment abnormalities, presence of a U wave, etc.

Cardiac Axis
• Net direction of electrical
activity during depolarization1
• Waveforms are recorded from
six frontal plane leads: I, II, III,
aVR, aVL and aVF
2
• Imaginary lines form intersect
at heart’s center and form
hexaxial reference system2
• Normal axis: 0° and +90°2
• LAD: 0° and –90°2
• RAD: +90° and +180°2
1. Ashley EA, Niebauer J. Cardiology Explained. London: Remedica, 2004.
2. ECG Interpretation made Incredibly Easy, 5th edn. Philadelphia: Wolters Kluwer Health Lippincott Williams and Wilkins, 2011.
Hexaxial Reference System
RAD: right axis deviation; LAD: left axis deviation

Cardiac Axis Determination: Quadrant Method
• Fast and easy method
• Involves examination of deflection of QRS complex in leads I and aVF

Quadrant Method: An Example
Lead I: Negative
deflection;
aVF: Positive
deflection=Right
axis deviation

Equiphasic Method
• More precise method
• Step 1: Identify the lead with equiphasic QRS complex
• Step 2: Locate the axis perpendicular to this lead on hexaxial
diagram
• Step 3: The axis of the identified lead represents heart’s electrical
activity in degrees

Causes of Axis Deviation
Left
• Normal variation
• Inferior wall myocardial infarction
(Ml)
• Left anterior hemiblock
• Wolff-Parkinson-White syndrome
• Mechanical shifts (ascites,
pregnancy, tumors)
• Left bundle branch block
• Left ventricular hypertrophy
• Aging
Right
• Normal variation
• Lateral wall Ml
• Left posterior hemiblock
• Right bundle branch block
• Emphysema
• Right ventricular hypertrophy

• Normal sinus rhythm is standard rhythm against which all
other rhythms are compared
• Characteristics of normal sinus rhythm
Normal Sinus Rhythm

Sinus Rhythms: Sinus Bradycardia
1. Huff J. ECG Workout: Exercises in Arrhythmia Interpretation, 5th edn. Philadelphia: Lippincott Williams and Wilkins, 2006.
Characteristic ECG
Features1
Occurs during sleep and in athletes2

Sinus Tachycardia
• Exercise
• Pain
• Stress
• Fever
• Strong emotions such as fear and anxiety
• Heart failure
• Cardiogenic shock
• Pericarditis
Characteristic ECG
Features1

Sinus Arrhythmia
• Occurs naturally in athletes and children
• Inferior wall myocardial infarction
• Advanced age
• Use of digoxin or morphine
• Conditions that increase intracranial pressure
Characteristic ECG
Features1

• Originates outside SA node
• Triggers: Alcohol, nicotine, anxiety, fatigue, fever and
infectious diseases, coronary or valvular heart disease,
acute respiratory failure, hypoxia, pulmonary disease,
digoxin toxicity, and certain electrolyte imbalances
• Characteristic ECG Features
 Rhythms: Irregular as a result of PACs
 P wave: Premature; may be buried in the previous T wave
 PR interval: Usually normal; may be slightly shortened or prolonged
 QRS complex: Similar to the underlying QRS complex when PAC is
conducted; may not follow the premature P wave when PAC is non-
conducted
Atrial Rhythms: Premature Atrial Contractions (PAC)

• Ectopic beat that may occur in healthy people
• PVCs may occur singly, in clusters of two or more, or in repeating
patterns such as bigeminy (every 2nd beat) and trigeminy (every 3rd
beat).
• When occurs with underlying heart disease, indicates impending lethal
ventricular arrhythmias
• Characteristic ECG Features
 Rhythms: Irregular during PVCs
 Rate: Patterned after underlying rhythm
 P wave: Absent
 PR interval: Unmeasurable
 QRS complex: Wide and bizarre
 T wave: Opposite direction from QRS complex
 QT interval: Unmeasurable
Ventricular Rhythms: Premature Ventricular
Contractions (PVC)

• Delayed conduction of atrial impulses through AV node
• Can occur normally in healthy persons or result from myocardial
ischemia, infarction, myocarditis, degenerative, medications, such
as digoxin, calcium channel blockers, and -adrenergic blockers
• Characteristic ECG features include a normal sinus rhythm except
for a prolonged PR interval
Heart Blocks: First-Degree Atrioventricular (AV) Block

• Also known as Mobitz type I block; each successive impulse from SA
node is delayed longer than previous impulse and finally fails to be
conducted.
• Occurs in coronary artery disease, inferior wall MI, rheumatic fever,
increased vagal stimulation, medications, such as digoxin, calcium
channel blockers and -adrenergic blockers.
• Distinguishing ECG features: Irregular ventricular rhythm with
ventricular rate exceeding atrial rate; PR interval gradually gets
longer with each beat until P wave fails to conduct.
Type I Second-Degree AV Block

Type II Second-Degree AV Block
• Also known as Mobitz type II block; more serious than type I
block
• Occasional impulses from SA node fail to conduct to the
ventricles
• Occurs in anterior wall MI, degenerative changes in the
conduction system, or severe coronary artery disease
• Distinguishing ECG features: Irregular ventricular rhythm is
observed when block is intermittent and regular if block is
constant, occasional prolonged PR interval and wide QRS
complex

• Also called as complete heart block; occurs when impulses from atria
are completely blocked at AV node and do not reach ventricles
• Congenital conditions: Originate at the level of AV node
• Occurs in coronary artery disease, anterior or inferior wall MI,
degenerative changes in the heart, digoxin toxicity, calcium channel
blockers, -adrenergic blockers or surgical injury
• Distinguishing ECG features:
 Rhythm: Regular
 Rate: Atrial rate exceeds ventricular rate
 PR interval: Variations with no regularity; no relation between P waves and
QRS complexes
 QRS complex: Normal in junctional pacemaker or wide and bizarre in
ventricular pacemaker
Third-Degree AV Block

Stable and Unstable Angina
• Typically shows ischemic changes on ECG but only during the angina
attack
• Since the changes are transient, ECG should be performed as soon
as the patient reports chest pain
• Helpful in identifying the affected coronary artery and thereby
preventing myocardial infarction or death

ECG Changes in Angina

Myocardial Infarction
• Myocardial infarction (MI) usually occurs in the left ventricle and
the location may vary based on the coronary artery affected
• ECG shows three pathological changes of an MI:
 Zone of ischemia
 Zone of injury
 Zone of infarction

Pathologic Zones in MI
• Zone of Infarction: Represents area of myocardial necrosis that is
irreversible and eventually replaced by scar tissue. ECG changes
include a pathologic permanent Q wave that results from lack of
depolarization
• Zone of Injury: Surrounds the zone of infarction seen as an elevated
ST segment on an ECG
• Zone of Ischemia: Outermost area seen as T-wave inversion
• Changes in zones of injury and ischemia are reversible
MI: myocardial infarction

ECG Changes during MI
• ECG may typically show an ST-segment elevation
• T waves flatten and become inverted
• Q waves appear hours to days after MI and indicate that the whole
thickness of myocardium has become necrotic
• Tall R waves can develop in reciprocal leads, which are known as
Transmural or Q-wave MI
• ST changes return to baseline within few days/2 weeks
• Inverted T waves persist for several months
• Q waves may stay for indefinite period

ECG Changes during MI
• For every characteristic
ECG change on the
damaged side, the ECG
shows opposite changes
on the reciprocal leads

Locating an MI
• Locating the MI is a critical factor in determining appropriate
treatment and in predicting complications.
Wall affected Leads Artery involved Reciprocal changes
Anterior V2 to V4 Left coronary artery, left anterior
descending (LAD) artery
II, III, aVF
Anterolateral I, aVL, V3 to V6 LAD artery, circumflex artery II, III, aVF
Septal V1 to V2 LAD artery None
Inferior II, III, aVF Right coronary artery I, aVL
Lateral I, aVL, V5, V6 Circumflex artery, branch of left coronary
artery
II, III, aVF
Posterior V8, V9 Right coronary artery, circumflex artery V1 to V4
Right ventricular V4R, V5R, V6R Right coronary artery None

Locating an Anterior Wall MI
Artery Involved:
Left coronary
artery, left
anterior
descending
(LAD) artery

Locating a Lateral Wall MI
Artery Involved:
Left circumflex
artery; branch of
left coronary artery

Locating an Anteroseptal Wall MI
A septal wall MI
commonly occurs along
with anterior wall MI as
left anterior descending
(LAD) artery also supplies
ventricular septum

Locating an Inferior Wall MI
• An inferior wall occurs
alone or along with lateral
wall MI or right ventricular
MI
• Inferior wall MI exhibits the
risk of developing into
sinus bradycardia, sinus
arrest, heart block, and
premature ventricular
contractions

Locating a Posterior Wall MI
Artery Involved:
Right coronary artery or
the left circumflex
arteries

Locating a Right Ventricular MI
• Occurs due to occlusion of
right coronary artery
• Right ventricular MI (RVMI)
usually occurs along with
inferior wall MI (about 40%
of times)
• RVMI can result in right-
sided heart failure and right-
sided block
• Identifying RVMI is difficult if
right precordial leads are not
available
• Leads II, III, and aVF or V1,
V2, and V3 may show ST-
segment elevation

Artifact
• When the baseline of the ECG appears wavy, bumpy, or tremulous
on the strip, it is known as an artifact.
What you see What might cause it What to do about it

• Electrical interference or 60-cycle interference appears as a thick
and unreadable baseline
Electrical Interference

Wandering Baseline
• Wandering baseline indicates that the waveforms are present but
the baseline is not stationary

Weak Signals

Other Problems
• Faulty equipment: Problems such as broken cables and lead wires
can cause improper grounding and result in a shock
• False high rate alarm: Can occur when gain setting is too high,
particularly with MCL1. In such cases, assess the patient for signs
and symptoms of hyperkalemia and reset the gain

Summary
• An ECG aids in the diagnosis and treatment of various cardiac and other
related disorders.
• The leads include standard limb leads, augmented limb leads, chest leads
and modified chest leads.
• ECGs can be interpreted by following a 5-step approach, which includes
determining rate, rhythm, evaluating P wave, duration of PR interval and
QRS interval.
• Some heart rhythm abnormalities include abnormalities in sinus rhythm,
atrial rhythm, ventricular rhythm and heart blocks.
• ECG changes are specific to cardiac conditions, such as acute coronary
syndromes and myocardial infarction.
• Characteristic ECG changes that occur with each type of MI-specific leads
help in locating the MI.
• Monitor problems in ECG, such as artifact, electrical interference,
wandering baseline, and can be recognized easily and managed well.

Case Study 1
• A 60-year-old man presented to OPD complaining of vague
central chest pain on exertion with no pain at rest.
Old inferior myocardial infarction

Case Study 2
• A 50-year-old man visited the emergency department with
complaint of severe central chest pain for the past 18 h.

Case Study 3
• A 75-year-old woman complained of attacks of dizziness.

Case Study 4
• This ECG was recorded from a 48-year-old man who had severe central
chest pain for the past 1 h.

Case Study 5
• This ECG was recorded from a 39-year-old woman who complained of
sudden onset of breathlessness. She had no previous history, and no
chest pain. Examination revealed nothing other than a rapid heart rate.

Case Study 6
• This ECG was recorded from a patient who was admitted with an acute
myocardial infarction 2 h back. The patient was cold and clammy and
confused and his blood pressure was unrecordable.

Case Study 7
• A 9-year-old girl underwent ECG due to the presence of
heart murmur on physical examination. She was
asymptomatic.

Case Study 8
• This ECG was recorded from a 55-year-old man who was admitted to
hospital as an emergency with severe central chest pain that had been
present for about an hour. He was pale, cold and clammy; his blood
pressure was 100/80 mmHg, but there were no signs of heart failure.

Case Study 9
• This ECG was recorded from a 25-year-old pregnant woman
who complained of an irregular heart beat. Auscultation
revealed a soft systolic murmur but her heart was
otherwise normal.

Case Study 10
• An 80-year-old woman had previously had a few attacks of
dizziness, fell and broke her hip. She was found to have low
pulse.

Ecg basics and interpretation

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