Please complete the ECG Lab assignment and follow assignment instruction carefully using provided data and supplemental documents. Please follow instructions on “Lab 2 Assignment”. For questions 1 and 2 please refer to “Lab 2 Manual” and “420 ECG Student”.
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Assignment-20 points
Purpose (1 point)
Resuits (18 points)
1.
Create a one-page worksheet for ECG interpretation (reminder: as usual, this must be done on
your own). Include a space for a nal interpretation. This worksheet format will be used to interpret
each ECG on question #5. (0.5 pt)
2.
Create a one-page/one-sided “cheat sheet” for ECG interpretation. You will be able to use this on
the Lab Final exam. (0.5 pt)
3
Using your cheat sheet from #2, interpret: (5 pts)
Lead ll rhythm strips 3a – 3e (found on the following pages).
calculations on the rhythm strips.
Make notes and show your
Yourrhythmstripinterpretationsshould incude
o6none9
heart rate
rhythm
4
Using your cheat sheet from #2, interpret: (5 pts)
Lead Il rhythm strips 4a –4e (found on the following pages).
calculations on the rhythm strips.
Make notes and show your
Your rhythm stripinterpretationsshould include:
heart rate
rhythm
premature beats
5.
Using your cheat sheet from #2 and the worksheet created in #1, interpret: (7 points total)
Your own 12-lead RESTING ECG (3.5 pts)
Ve workseet fram Ql
The 12-lead EXERCISE ECG from your group (3.5 pts)
Your 12-eadinterpretationsshouldincude (1worksheetperECGinterpretation!):
Three steps (heartrate, rhythm, and premature beats)e
Axis determination
Enlargements (if applicable)
Hypertrophies (if applicable)
Previous MI (if applicable)
•
Attach the ECG tracings to the lab report.
Notes ontheworksheet mustbedetailedenoughto justifyyourinterpretationsand calculations.
Closing Paragraph (1 point)
63
Lead lIl Rhythm Strips
ForQuestion#3:
3a.
Heart Rate:
Rhythm:
36.
Heart Rate:
Rhythm:
3c.
Heart Rate:
Rhythm:
64
3d.
Heart Rate:
Rhythm:
3e.
Heart Rate:
Rhythm:
65
ForQuestion#4:
4a.
Heart Rate:
Premature BeatInterpretation:
Rhythm:
4b.
Heart Rate:
Premature Beat Interpretation:
Rhythm:
4c.
Heart Rate:
Premature Beat Interpretation:
Rhythm:
66
4d.
Heart Rate:
Premature Beat Interpretation:
Rhythm:
4e.
Heart Rate:
Premature Beat Interpretation:
Rhythm:
67
To gain knowiedge and understanding of the scienti c principle and concept of:
electrocardiography.
depolarization and repolarizationin the heart.
2.
To learn how to interpret and apply:
A 12-lead ECG at rest and during exercise (basic interpretation).
3.
To lean and develop the following speci c skills:
How to administer an electrocardiograph test.
Introduction
An electrocardiogram is a recording of the electrical activity of the heart. Electrical impulses generated in
the heart are conducted through body uids to the skin, where they can be detected and printed out by an
electrocardiograph.
Infomation We GetFrom a RhythmStrip:
Rate & rhythm
Presence of any blocks
Presence of any irregular/premature beats
Additional Information We Get From a Resting 12-Lead ECG: (full view of heart)
Anatomical orientation of the heart in the body (axis)
Relative thickness of the heart muscle and the size of the chambers (hypertrophy/enlargement)
Previous damage to the heart (myocardial infarction, MI) (Qwave)
Acute MI (ST-segment elevation)
Infomation We GetFromanExercise12-LeadECG:
exercise→↑HR-→↑02 demand by heart → ischemia (if CAD is present) → ST-segment depression
The Wave ofDepolarizationNormallyTravelsThroughthe Heartas Follows:
Impulse originates at the SA node (in right atrium) which starts the wave of depolarization
Spreads across the left and right atria (atria depolarize and contract)
Goes into the AV Junction (electrical “bridge” connecting atria and ventricles, includes AV node and
bundle of HIS) where it pauses for ~ 0.13 seconds to wait for atrial contraction/ventricular lling to be
completed
Goes down the left and right þundle branches (carries stimulus into ventricles toward apex of heart,
then outward)
To the Purkinje bers (on both left and right sides)
Throughout the left and right yentricles (ventricles depolarize and contract)
The ventricles repolarize and relax
The cycle begins again.
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1.
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Speci c Objectives
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Lab #2:Electrocardiography(ECG)
. Ade ection
thatispartly
positiveandpartly
negativeisclledbiphasi. b
The
o
ool
sinus node (normal pacemaker) impulse immediately precedes the P wave, but is not visible on an
ECG.
P wave
o
Representsatrial
depolarization(contraction).oor
o
Small de ection before QRS complex.
peub onsiesnie
dote&hA
P-R interval
o
o
Measured from the beginning of the P wave to the beginning of the QRS complex.
Represents the time it takes for the stimulus to spread through the atria and to pass through the
AV junction.
otosbensct
QRS complex
Represents ventricular depolarization (contraction).
o
o
o
o
o
o
QRS width represents the time required for a stimulus to spread through the ventricles.
Not every QRS containsa Q wave, an R wave, and an S wave.
If the initial de ection of the QRS complex is negative, it is called a Q-wave.
The rst positive de ection in the QRS complex is called an R wave.
A negative de ection following the R wave is called an S wave.
Atrialrepolarization occurs here but is hidden within the QRS complex.
en
ST segment
o
o
Measured from the end of the QRS complex to the beginning of the T wave.
Represents the beginning of ventricular repolarization.
A normal ST segment is isoelectric.
J point
o
The junction between the QRS complex and the beginning of the ST segment
Twave
o
Represents ventricular repolarization.
QT interval
o
Measure from the beginning of the Q wave to the end of the T wave.
Represents the ventricular refractory period (time necessary for the ventricle to depolarize, then
repolarize).
U wave
Small de ection sometimes seen after the T wave.
Exact action unknown.
Represents the nal phase of ventricular repolarization.
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03E)vishipofbmsoaash3 ch dnl
An upward de ection or wave is called positive.
A downward de ection or wave is called negative.
A de ection or wave that rests on the baseline is called isoelectric.
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Basic ECGWaves
Figure 1.
1.0
PRsogment
P-R interval
HHH
Isoelectric line
+
-Tinterval
„04
0.2
0.4
0.6
0.8
Soconds
ECG Leads
The body conducts electricity. Therefore, recording electrodes placed on the body are able to detect the
voltages of the cardiac currents conducted to these locations. The usual way of recording the voltages
from the heart is with 12 standard ECG leads. Each lead shows a “picture” of the difference in electrical
potential (voltage) between two points on the skin surface (electrodes). Each lead is measuring the same
event (one cardiac cycle) simultaneously, but each lead viewsit from a different angle. Multiple ECG leads
describe the electrical activity from multiple angles/views to allow a complete picture of the heart’s electrical
activity.
54
The leads can be divided into two subgroups:
1. Extremity(limb)Leads
These leads show voltage differences by placing electrodes on the limbs (4 electrodes total). During a
resting ECG the electrodes are placed on the extremities. During an exercise ECG the arm electrodes
are placed below the clavicles and the leg electrodes on the lower abdomen.
The extremity leads can be further divided into two smaller subgroups:
a. Bipolarextremityleads
The right leg electrode is the electrical ground.
Lead I records the voltagedifferencebetween the left arm (LA) and right arm (RA).
Lead |= LA – RA
Example: When recording lead , the LA electrode detects the electrical voltages of the heart
transmitted to the left arm. The RA electrode detects electrical voltages of the heart transmitted
to the right arm. The electrocardiograph subtracts the RA voltages from the LA voltages. The
difference between these voltages appears at lead l on the prnt-out.
Lead ll records the voltage difference between the left leg (LL) and right arm (RA).
Lead I| = LL- RA
Lead lI records the voltage differencebetween the left leg (LL) and left arm (LA).
Lead Ill = LL- LA
Einthoven’s Triangle
LA
RA
LL
b. Unipolarextremityleads
The three unipolar leads are aVR, aVL, and aVe.
The ‘a” stands for “augmented”, the”V stands for “voltage”, and the R, L, and F stand for Right
arm, Left am, and left Foot.
The unipolar leads record the electrical voltage at one location relative to zero potential, rather
than relative to another extremity.
2. Precordial(chest)Leads
These leads show voltage differences by placing electrodes on the chest (6 electrodes total). The six
precordial leads are V1, V2, V3, V4, V5, and V6. The precordial leads are unipolar leads that record
the electrical voltage at one location relative to zero potential.
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2.
A negative de ection will appear in any lead if the wave of depolarization spreads toward the negative
pole of that lead (or away from the positive pole).
3.
A biphasic de ection will appear if depolarization spreads at right angles to any lead axis.
SkinPrep:
1.
2.
3.
4.
If necessary, shave hair.
Clean the skin surface thoroughly with alcohol.
Scrape off dead skin using gauze.
Let the alcohol dry before applying the electrode.
Place electrodes as lows:
Limb Leads (restingECG)
R/ arm anterior surface of right wrist
V arm anterior surface of left wrist
R/ leg on top of at portion of the right tibia superior to the medial maleolus (ground)
U leg on top of at portion of the left tibia superior to the medial maleolus
Limb Leads(exerciseECG)
R/ambelowright
clavicle,offof muscleoenhisoo oovh
N RI leg below rib cage on right side of abdomen (ground)o
tioreoe
Varm belowleftclavicle,offof musclec
U leg
below rib cage on left side of abdomen
o
oes
o 0
h
o
o
2uslush
Precordial Leads (resting orexercise ECG)- (see Figure 2)
V1
V2
V3
V4
V5
V6
on the right side of the sternum in the fourth intercostal space
on the left side of the sternum in the fourth intercostal space
on a diagonal, midway between V2 and V4
left mid-clavicular line in the fth intercostal space
left anterior axillary line, horizontal to V4
left mid-axillary line, horizontal to V4 & V5
How tolocatethe fouthintercostalspace:
Place your nger at the top of the sternum and move it slowly downward. After moving about 1-% inches
you will feel a slight horizontal ridge; this is called the angle of Louis, where the manubrium joins the body
of the sternum. The second intercostal space is just below and lateral to this point. Move down two more
spaces to the fourth intercostal space.
Femalesubiects:
When placing electrodes on a female, you must place V4-V6 blow the breast. To avoid breast tissue, V3
will also be lower on a female than on a male, but you should place it as lose as you can to the diagonal
between V2 and V4,
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A positive de ection will appear in any lead if the wave of depolarization spreads toward the positive
pole of that lead.
The skin must be properly prepared before placing the electrodes onto the skin surface in order to ensure
a clean transfer of electrical impulses from the skin to the electrode.
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1.
ECG Electrode Placement
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get
ThreeBasicLawsofElectrocardiographv.
Figure 2.
V6
(From American College of SportsMedicine, ACSMS ResourceManual, 3’ Ed. Wiliams & Wikins. 1998,)s
ECG Paper and Heart Rate
On ECG paper, each small box is 1 mm² and each large box is 5 mm?.
Amplitude, or voltage, of ECG waves/de ections is measured in the vertical direction.
The ECG is standardized so that 1 mV produces a de ection of 10 mm amplitude (10 mm/mV)
(default setting). If the amplitudes are too high or t0o low, the sensitivity can be adjusted.
Width (duration) is recorded in the horizontal direction.
ECG chart paper usually moves at 25 mmis (default setting). The paper speed can be changed.
Each mm of ECG paper is equal to 0.04 seconds (25 mm/sec X 0.04 seconds = 1 mm).
Each 5 mm of ECG paper is equal to 0.20 seconds (5 X 0.04 seconds = 0.20 seconds).
Two methods for calculating (average) heart rate from an ECG tracing:
1.
If the heart rate is reqular (regular R to R intervals):he
Count the number of large boxes between two successive QRS complexes and divide 300 by
this. The number of large boxes is divided into 300 because 300 X 0.20 = 60 and we are
calculating the heart rate in beats per minute, or 60 seconds.
For a more accurate measure, count the number of small boxes between successive QRS
Complexes and divide 1500 by this. The number of small boxes is divided into 1500 because
1500 X 0.04 = 60 and we are calculating the heart rate in beats per minute, or 60 seconds.
2.
If the heart rate is irreqular (irregular R to R intervals):
Count the number of cardiac cycles (1 cardiac cycle is the interval between successive R
waves) in a six-second period and multiply this number by 10 (since 6 seconds X 10 = 60
seconds or 1 minute). To determine 6 seconds: 6 seconds = 30 large boxes. This will give the
beats per minute because ten 6-second strips is equivalent to one minute.
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ECG Interpretation
(For speci c examples, see ECG tracings in the Appendix at the end of your lab manual)
For steps 1-3, use a rhythm strip.
Step 1: Determine the Underlying Rate
“Underlying” means the primary rhythm, excluding any iregular beats.
Is theratenormal?(60-100bpm)
NO→ I
M
heart rate less than 60 bpm → bradycardia
heart rate greater than 100 bpm → tachycardia
Step 2: Determine the Underlying Rhythm
Inspect the P-Waves (of the underlying rhythm). It is helpful to circle all of the P-waves.
Are P-wavespresent for eachQRS? Are theP-wavesupright?
YES to both → sinus rhythm (impulse originates at SA node; normal focus)
normal rate & regular rhythm → normal sinus rhythm (NSR)
normal rate & irregular rhythm → sinus arrhythmia
rate < 60 bpm & regular rhythm → sinus bradycardia
rate > 100 bpm & regular rhythm → sinus tachycardia
Inverted P-waves → junctional” rhythm (impulse originates at AV node; ectopic focus)
No p-waves & normal QRS width -→ junctional” rhythm
No p-waves & wide QRS (>0.12) → ventricular rhythm
(*In a junctional rhythm, the P-waves are inverted or absent because they occur within QRS complex.)
|Step 3: Determine whether there are any Premature Beats
A premature beat is a beat that comes before the next nomal/sinus beat is due.
Are theresignsofprematurebeats?
YES → determine origin (inspect P-waves and QRS complex)
normal, upright P-wave & normal QRS width -→ PAC (see description below)
no P-wave& wide &aberrantQRS → PVc (seedescriptionbelow)
When there is a premature beat:
Include the underlying rhythm in your interpretation, (example: normal sinus rhythm
with PVC’s, sinus bradycardia with PJC’s)
Look for a pattern in the premature beats (see below)
If therearePVC’s,isthefocusuni-ormulti-focal?(seebelow)
If there are premature beats, do they have a Pattern?
Ø
Ø
Ø
two consecutive premature beats → couplet
three consecutive beats
triplet
four or more consecutive beats → ventricular tachycardia
every other beat is premature → bigeminy
every third beat is premature→ trigeminy
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PrematureBeats
Premature Atrial Contraction (PAC)- Impulse originates in atria, but not from SA node.
nomal P-waves or P-waves not visible (lost in T-wave)
nomal QRS width
Premature Ventricular Contracion (PVC) -Impulse originates in the ventricles.
no P-wave, wide and aberrant QRS, >0.12 second
T-wave and QRS complex usually point in opposite directions
three or more PVC’s in a row= ventricular tachycardia
PVCFocus
Unifocal PVC’s – originate from same ectopic (abnormal) focus (pacemaker location) in ventricles.
PVC’s that look the same
Multifocal PVC’s – originate from more than one ectopic focus in ventricles.
PVC’s that look different
Additional Information Obtained from a 12-Lead ECG
Axis (see gure 3)
Is the QRS complex in lead I positive or negative?
positive → axis in left quadrant
negative → axis in right quadrant
Is the QRS complex in lead AVF positive or negative?
positive → axis in bottom quadrant
negative → axis in top quadrant
Determine the quadrant.
lower left→ normal axis
upper left→ left axis deviation (LAD)
lower right → right axis deviation (RAD)
upper right → extreme right axis deviation
59
Figure 3.
LA
AVF7
AVF4
Norm
AVFJ
AVF
(From: Dubin, D. Rapid Interpretation of EKG’s, S Ed. Cover Publishing Company, 2000,)
Enlargement
Check p-waves in limb leads and V1.
•
p-wave tall (>2.5 mm) in any limb lead → right atrial enlargement (RAE)
p-wave inverted or biphasic in V1
&lor
Humped p-wave in one or more of the limb leads
→ left atrial enlargement (LAE)
Hypertrophy
Check R& S-waves in V1, V5, and V6.
Tall R-wave in V1 (taller than S-wave) → right ventricular hypertrophy (RVH)
(S in V1) + (R in V5 or V6) > 35 mm → left ventricular hypertrophy (LVH)
Previous MI
Scan leads for Q-waves.*
Signi cant Qwave (2 1/3 of the amplitude of the QRS complex) → MI (old or acute)
AcuteMI
Scan leads for ST-segment elevation.*
Elevation→ acute MI
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Additional Information Obtained from a 12-Lead Exercise ECG
Ischemial/CAD
Scan leads for ST-segment depression.”
İschemia→ CAD
0.5 mm
*Leads with Abnormality
Location of Abnormality
V1, V2
Anteroseptal
V1-V4
Anterior
V1-V6, 1,AVL
Extensive anterior
V3- V6,IAVL
Anterolateral
I.AVL
High lateral
II, III, AVF
Inferior
V1, V2
Posterior
OtherReferences:
4.
Aehlert, B. ECGS Made Easy, 2rd Ed. Mosby, Inc Publishing. 2002.
American College of Sports Medicine, ACSM’s Resource Manual, 3rd Ed. Willians & Wilkins. 1998.
Dubin, D. Rapid Interpretation of EKG’s, Sh Ed. Cover Publishing Co. 2000.
Ford, R.D. EKG Cards. Springhouse Publishing Co. 1987.
5.
Goldberger, A.L. and Goldberger, E. Clinical Electrocardiography: A Simpli ed Approach, 3d Ed. C.V. Mosby Co. 1986.
2
3
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Procedures
Equipment
Electrocardiograph
Recording paper
Electrodes
Alcohol wipes
Folding cot
Themo Tape
Ace Bandages
Fom 4 groups, no more than 4 students/group.
Part 1:RESTINGECG
Perfom a resting ECG on each person in your group.
o
o
This should be done as the subject rests comfortably on a massage table.
Take your time and be sure to place the electrodes correctly.
The electrodes require a smooth surface. Shave any chest hair as necessary.
Give the subject time to relax to obtain a true “resting” value.
Part 2:EXERCISEECG
Perfon an exercise ECG on one person in your group.
The subject may choose their exercise device and intensity.
(Note: it is easier to obtain a clear
reading with less “bounce”.)
Be sure that your subject has reached a steady-state exercise heart rate before recording. (This
can be measured manually at the wrist.)
o
Take your time and utilize the provided materials (tape, ace bandages, etc.) to obtain a clear tracing
that is relatively “noise-free”. You may have to make multiple attempts.
62
Electrocardiogram (ECG)
HBIO 420L
Bara Floyd
Normal Electrocardiogram
Figure 9.11
Electrocardiogram (ECG)
¤
Records the electrical activity of the heart
¤
P wave
¤ Atrial depolarization
¤
P-R Interval
¤ Time required for signal to spread
through atria
¤
QRS complex
¤ Ventricular depolarization and atrial
repolarization
¤
ST Segment
¤ Beginning of ventricular repolarization
(normally isoelectric)
¤
T wave
¤ Ventricular repolarization
Relationship Between Electrical Events
and the ECG
Figure 9.12
ECG Leads: Extremity Leads
ECG Lead Placement: Rest vs. Exercise
ECG Interpretation: Step 1
Determine the underlying rate:
¤ “Underlying” means the primary rhythm, excluding any
irregular beats.
¤ Is the rate normal? (60-100 bpm)
¤ NO :
¤ heart rate less than 60 bpm → bradycardia
¤ heart rate greater than 100 bpm → tachycardia
ECG Interpretation: Step 2
Determine the underlying rhythm:
¤
Inspect the P-Waves (of the underlying rhythm). It is helpful to circle all of the Pwaves.
¤
Are P-waves present for each QRS? Are the P-waves upright?
¤ YES to both
¤
¤
¤
¤
¤
sinus rhythm (impulse originates at SA node; normal focus)
¤
normal rate & regular rhythm → normal sinus rhythm (NSR)
¤ normal rate & irregular rhythm → sinus arrhythmia
¤
rate 100 bpm & regular rhythm → sinus tachycardia
Inverted P-waves → junctional* rhythm (impulse originates at AV node; ectopic focus)
No p-waves & normal QRS width ® junctional* rhythm
No p-waves & wide QRS (>0.12) → ventricular rhythm
(*In a junctional rhythm, the P-waves are inverted or absent because they occur within QRS
complex.)
ECG Interpretation: Step 3
Determine whether there are any premature beats:
¤
A premature beat is a beat that comes before the next normal/sinus beat is due.
¤
YES: determine origin (inspect P-waves and QRS complex)
¤
¤
¤
¤
normal, upright P-wave & normal QRS width ® PAC (see description below)
no P-wave & wide & aberrant QRS ® PVC (see description below)
When there is a premature beat:
¤
include the underlying rhythm in your interpretation, (example: normal sinus rhythm with PVC’s, sinus
bradycardia with PJC’s)
¤
look for a pattern in the premature beats (see below)
¤
if there are PVC’s, is the focus uni- or multi-focal? (see below)
If there are premature beats, do they have a Pattern?
¤
two consecutive premature beats → couplet
¤
¤
three consecutive beats → triplet
four or more consecutive beats → ventricular tachycardia
¤
¤
every other beat is premature → bigeminy
every third beat is premature → trigeminy
Premature Beats
Premature Atrial Contraction (PAC)
¤ Impulse originates in atria, but not from SA node.
¤ normal P-waves or P-waves not visible (lost in T-wave)
¤ normal QRS width
Premature Ventricular Contraction (PVC)
¤ Impulse originates in the ventricles.
¤ no P-wave, wide and aberrant QRS, >0.12 second
¤ T-wave and QRS complex usually point in opposite directions
¤ three or more PVC’s in a row = ventricular tachycardia
¤ PVC Focus
¤ Unifocal PVC’s – originate from same ectopic (abnormal) focus
(pacemaker location) in ventricles
¤ PVC’s that look the same
¤ Multifocal PVC’s – originate from more than one ectopic focus in
ventricles
¤ PVC’s that look different
ECG Interpretation: Step 4
Determine orientation of axis:
ECG Interpretation: Step 5
Determine if there is any atrial enlargement:
¤ Check p-waves in limb leads and V1.
¤ p-wave tall (> 2.5 mm) in any limb lead
¤ right atrial enlargement (RAE)
¤ p-wave inverted or biphasic in V1
&/or
¤ humped p-wave in one or more of the limb leads
¤ left atrial enlargement (LAE)
ECG Interpretation: Step 6
Determine if there is any ventricular hypertrophy:
¤ Check R & S-waves in V1, V5, and V6.
¤ Tall R-wave in V1 (taller than S-wave)
¤ right ventricular hypertrophy (RVH)
¤ (S in V1) + (R in V5 or V6) > 35 mm
¤ left ventricular hypertrophy (LVH)
ECG Interpretation: Step 7
Determine presence of previous or acute MI:
¤ Scan leads for Q-waves.
¤ Significant Q-wave (³ 1/3 of the amplitude of the QRS
complex)
¤ MI (old or acute)
¤ Scan leads for ST-segment elevation.*
¤ Elevation
¤ acute MI
ECG Interpretation: Step 8
Determine presence of Ischemia/CAD:
¤ Scan leads for ST-segment depression.*
¤ ³ 0.5 mm ® ischemia ® CAD
Leads with Abnormality
Location of Abnormality
V1, V2
V1 – V4
Anteroseptal
Anterior
V1 – V6, I, AVL
V3 – V6, I AVL
I, AVL
II, III, AVF
Extensive anterior
Anterolateral
High lateral
Inferior
V1, V2
Posterior
S-T Segment Depression on the
Electrocardiogram
Figure 9.10
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