ECGG Interpretation Najib Ul Haq coyright 2004 Anna Story

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 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

Atrial depolarization 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 - + Lead III Lead II 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 Lateral portion of the heart Some leads get a good view of the: Anterior 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.

A Normal 12 Lead ECG 2004 Anna Story

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 Lateral portion of the heart Anterior portion of the heart Lateral portion of the heart Inferior portion of the heart Look again at this picture of the heart.

MI Locations Lateral portion of the heart Anterior portion of the heart Lateral portion of the heart Inferior portion of the heart Look again at this picture 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

View of Anterior Heart Wall 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? Leads I, aVL, and V5- V6 Limb Leads Augmented Leads Precordial Leads

View of Lateral Heart Wall 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? Leads II, III and aVF Limb Leads Augmented Leads Precordial Leads

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

Thank You