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ECGG Interpretation

Najib Ul Haq

ECG

• 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 ConductionSinoatrial node

AV node

Bundle of His

Bundle Branches

Purkinje fibers

Impulse Conduction & the ECGSinoatrial 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

• T wave - Ventricular repolarization

• QRS - Ventricular depolarization

Normal ECG

Normal ECG

Lead Iextends from the right to the left arm

Lead IIextends from the right arm to the left foot

Lead IIIextends from the left arm to the left foot

Einthoven’s Triangle

+-

+

-

Diagnosing MI

To diagnose a myocardial infarction you need to go beyond looking at a rhythm strip and obtain a 12-Lead ECG.

Rhythm Strip

12-Lead ECG

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

Lateral portion of the heart

Inferior portion of the heart

ST Elevation

One way to diagnose an acute MI is to look for elevation of the ST segment.

192004 Anna Story

A Normal 12 Lead ECG

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 ArteryBranches 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

Lateral portion of the heart

Inferior portion of the heart

MI Locations

Look again at this picture of the heart.

Anterior portion of the heart

Lateral portion of the heart

Inferior 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

• Leads V3, V4– Looks at anterior heart wall– Looks from the left anterior chest

Anterior Wall MI

View of Anterior Heart Wall

Lateral MI

So what leads do you think the lateral portion of the heart is best viewed?

Limb Leads Augmented Leads Precordial Leads

Leads I, aVL, and V5- V6

• Leads I and aVL– Looks at lateral heart wall – Looks from the left arm toward

heart

Lateral Wall MI

View of Lateral Heart Wall

*Sometimes known as High Lateral*

Inferior MI

Now how about the inferior portion of the heart?

Limb Leads Augmented Leads Precordial Leads

Leads II, III and aVF

• Leads II, III, aVF- Looks at inferior heart wall

Inferior Wall MI

View of 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 MIThis 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 (V2-V4) and the lateral wall (V5-V6, I, and aVL)!

Thank You