ECG Axis Determination Module

ECG Axis Determination

Thomas E. O'Brien
AS CCT CRAT RMA

Learning Objectives

Upon completion of the accompanying narrative and practice the student will be able to:

Recall which major coronary artery supports each region of the heart
Associate the views of a 12-Lead ECG with specific surfaces of the heart
Determine the presence of cardiac axis deviation
Understand Einthoven's Triangle

12-Lead ECG

People may choose to analyze ECG’s in a number of different ways. The sequence doesn’t necessarily matter as long as you gather and report the proper information each time. I read from left to right as much as possible (in anatomic groupings).
If your protocols are different, always follow them.
The following slides will review the leads, surfaces, and associated coronary arteries which commonly supply that portion of the heart.

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Lessons

Lesson #1: Views 322

II, III, and aVF

Inferior wall of left ventricle
Right Coronary Artery
Marginal branch

V1 and V2

Septum
Left Coronary
Septal branch

V3 & V4

Anterior
Left Coronary
Anterior Descending and Diagonal arteries

I, aVL, V5 & V6

Lateral
Left Coronary
Circumflex & Obtuse marginal

Labeled Views

Lesson #2: Quick Check Views 1

Question 1

Name the inferior view leads.

Answer

II, III & aVF

Question 2

Name the septal view leads.

Answer

V1 & V2

Lesson #3: Quick Check Views 2

Question 1

Name the anterior view leads.

Answer

V3 & V4

Question 2

Name the lateral view leads.

Answer

I, aVL, V5 & V6

Lesson #4: Axis & Deviation

Description

Axis is the general flow of electricity as it passes through the heart from the SA node all the way to the Purkinje fibers.
It is typically obtained from the limb or frontal plane leads.
The axis of the heart can change for a number of different reasons from birth defects which affect the physical location of the heart i.e. Dextrocardia, to obesity to pregnancy among others.
If you can envision a circle with a centered vertical and horizontal line superimposed over the chest, you would note that the normal heart is located in the lower left quadrant of this circle.
You will be provided an example of this image in a few slides.

Electrical Axis Determination

Axis determination can be determined a number of different ways. From complex to simple. The following steps are the easiest I know to obtain this important information.

Electrical Axis Determination

Imagine a large circle, divided into four equal quadrants superimposed over the patient’s chest.

Lesson #5: Axis Determination

Part I

The direction of the ventricular depolarization (QRS complex) is analyzed.
Refer to lead I and aVF each time
If the majority of the QRS complex is positively deflected in both views, this is referred to as “normal axis”.

Part II

If lead I is positive and aVF is negative, this is ‘left axis deviation”

Part III

If lead I is negative and aVF is positive, this is “right axis deviation”.

Part IV

If lead I is negative and aVF is negative, this is extreme right axis deviation aka indeterminate.

Lesson #6: Quick Check Axis 1

Question

Identify the electrical axis

Answer

Normal Axis – Lead I up, aVF up

Question

Identify the electrical axis

Answer

Despite the presence of premature ventricular complexes, when analyzing the ventricular depolarization of the underlying rhythm you will note Normal Axis – Lead I up, aVF up