ECGG Interpretation
Najib Ul Haq
1
ECG
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ECG Basics
Normal Sinus Rhythm
How to Analyze a Rhythm
Heart Arrhythmias
Diagnosing a Myocardial Infarction
Advanced 12-Lead Interpretation
Normal Cardiac Current Flow
Basics of Current movement
• Current
• Electrode
+
Electrode
Current
Normal ECG
Normal Impulse Conduction
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers
Impulse Conduction & the ECG
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers
The PR Interval
Atrial depolarization
+
Delay in AV junction
(AV node/Bundle of His)
(Delay allows time for the
atria to contract before
the ventricles contract)
The “PQRST”
• P wave - Atrial
depolarization
• QRS -
Ventricular
depolarization
• T wave - Ventricular
repolarization
Normal ECG
Normal ECG
Einthoven’s Triangle
Lead I
extends from
the right to the
left arm
-
+
Lead III
extends from the left
arm to the left foot
Lead II
extends from the
right arm to the
left foot
+
Diagnosing MI
To diagnose a myocardial infarction you need
to go beyond looking at a rhythm strip and
obtain a 12-Lead ECG.
12-Lead
ECG
Rhythm
Strip
The 12-Lead ECG
• The 12-Lead ECG sees the heart from 12
different views.
• Therefore, the 12-Lead ECG helps you
see what is happening in different
portions of the heart.
• The rhythm strip is only 1 of these 12
views.
The 12-Leads
The 12-leads include:
–3 Limb leads
(I, II, III)
–3 Augmented leads
(aVR, aVL, aVF)
–6 Precordial leads
(V1- V6)
Normal ECG
Views of the Heart
Some leads get a
good view of the:
Anterior portion
of the heart
Inferior portion
of the heart
Lateral portion
of the heart
ST Elevation
One way to
diagnose an
acute MI is to
look for
elevation of the
ST segment.
A Normal 12 Lead ECG
2004 Anna Story
19
ST Elevation (cont)
Elevation of the ST
segment (greater
than 1 small box) in
2 leads is
consistent with a
myocardial
infarction.
Left Main Coronary Artery
Branches quickly into the LAD & LCX.
Involves almost 2/3 of the heart muscle
primarily anterior
Right Coronary Artery (RCA)
The RCA supplies blood to the bottom
(inferior) portion and part of the back
(posterior) portion of the left ventricle.
The posterior portion of the septum is also
supplied with blood from the RCA.
•SA Node 55%
•AV Node 90%
•AV Blocks
Left Anterior Descending Branch (LAD)
The LAD supplies blood to the front
(anterior) portion of the left ventricle, apical
including most of the anterior portion of the
septum separating the ventricles.
•Bundle Branch Block, AMI, CHF
Left Circumflux Branch (LCX)
The LCX supplies blood to the left
side (lateral) portion and the back
(posterior) portion of the left ventricle.
•SA Node 45%
•AV Node 10%
•Lateral & posterior MI
MI Locations
Look again at this
picture of the heart.
Anterior portion
of the heart
Inferior portion
of the heart
Lateral portion
of the heart
MI Locations
Look again at this
picture of the heart.
Anterior portion
of the heart
Inferior portion
of the heart
Lateral portion
of the heart
Anterior View of the Heart
The anterior portion of the heart is best
viewed using leads V1- V4.
Anterior MI
Remember the anterior portion of the heart is best
viewed using leads V1- V4.
Limb Leads
Augmented Leads
Precordial Leads
Anterior Wall MI
View of Anterior Heart Wall
• Leads V3, V4
– Looks at anterior heart wall
– Looks from the left anterior chest
Lateral MI
So what leads do you think the
lateral portion of the heart is
best viewed?
Limb Leads
Augmented Leads
Leads I, aVL, and V5- V6
Precordial Leads
Lateral Wall MI
View of Lateral Heart Wall
• Leads I and aVL
– Looks at lateral heart wall
– Looks from the left arm toward
heart
*Sometimes known as High Lateral*
Inferior MI
Now how about the inferior
portion of the heart?
Limb Leads
Augmented Leads
Leads II, III and aVF
Precordial Leads
Inferior Wall MI
View of Inferior Heart Wall
• Leads II, III, aVF
- Looks at inferior heart wall
-Looks from the left leg up
Putting it all Together
Now, where do you think this person is having
a myocardial infarction?
Inferior Wall MI
This is an inferior MI. Note the ST elevation in
leads II, III and aVF.
Inferior Wall MI
This is an inferior MI. Note the ST elevation in leads II, III and aVF.
Inferior Wall MI
Putting it all Together
How about now?
Anterolateral MI
This person’s MI involves both the anterior wall (V2V4) and the lateral wall (V5-V6, I, and aVL)!
Thank You