12 lead-lesson 2

12-Lead 12-Lead ElectrocardiographyElectrocardiography

a comprehensive course

Adam Thompson, EMT-P, A.S.Adam Thompson, EMT-P, A.S.

Lesson

2

Resources

• http://www.blaufuss.org/ECGviewer/indexFrame2.html• ems12lead.com/

http://www.blaufuss.org/ECGviewer/indexFrame2.html

http://wwwems12lead.com/

The 6-Step Method

• 1. Rate & Rhythm1. Rate & Rhythm

• 2. Axis Determination2. Axis Determination

• 3. Intervals3. Intervals

• 4. Morphology4. Morphology

• 5. STE-Mimics5. STE-Mimics

• 6. Ischemia, Injury, & Infarct6. Ischemia, Injury, & Infarct

Lesson Two

• Frontal Axis determination tutorial

• Precordial Axis rotation

• Pathologies that cause axis deviation

Objectives

• Learn how to determine the frontal axis.

• Distinguish between the different causes of axis deviation.

• Learn how to identify rotation of the precordial axis.

Axis Determination

• Critical Skill!• Use the hexaxial reference system for

the frontal plane.• Identify clockwise or counterclockwise

rotation of R-wave progression.

PathologiesFrontal Plane Axis Precordial Axis

ERAD-90 to 180

Right Axis Deviation90 to 180

Pathological Left Axis Deviation-30 to -90

Early TransitionCounterclockwise

Rotation

Late TransitionClockwise Rotation

• Ventricular Rhythm• Paced Rhythm• Dextrocardia• Electrolyte derangement

• May be normal• LPFB• Pulmonary disease• RVH• RBBB• WPW• Dextrocardia•Venrticular Rhythm

• Pregnancy• LAFB• WPW• Pulmonary disease• LBBB• Hyperkalemia• Q-waves, MI

• Posterior wall infarction• RVH• RBBB

• Sometimes Normal, especially in women• Anterior MI• LVH• LAFB• LBBB• Lung Disease

Willem Einthoven

Won the Nobel Prize in Physiology or Medicine in 1924 for inventing the string galvanometer which was the first EKG.

Einthoven’s Triangle

• Electrically, leads I, II, & III form an equilateral triangle.

• Einthoven’s LawI + (-II) + III = 0

Einthoven’s Law

• How it works

• Lead I– The R wave is about 7 1/2 mm tall.– The S wave is about 2 1/2 mm deep.

– Subtract the S wave from the R wave • you come up with 5 mm.

Einthoven’s Law

• Lead I = 5mm

• Lead II– It’s essentially a monophasic

QS complex. – About -10 mm.

Einthoven’s Law

• Lead I = 5mm

• Lead II = -10mm

• Lead III– R wave that is about 1 mm high.– The S wave is about 16 mm deep. – Subtract the S wave from the R wave.– -15 mm.

Einthoven’s Law

• Lead I = 5mm

• Lead II = -10mm

• Lead III = -15mm

Einthoven’s Law

• Lead I = 5mm

• Lead II = -10mm

• Lead III = -15mm– Plug the numbers in.

• I + (-II) + III = 0• 5 + 10 -15 = 0

Einthoven’s Law

The equilateral triangle

Electrical Axis

What is the heart’s electrical axis?

The first area to depolarize (1) is the interventricular septum

1

3

22

3

4

Mean vector

Cardiac vector

Electrical Axis


Next, the area around the left and right ventricular apex (2) depolarizes from a endocardial-to-epicardial direction (inside-out).

1

3

22

3

4

Mean vector

Cardiac vector

Electrical Axis


Finally, the lateral walls of the left and right ventricle depolarize (3) and last the high lateral wall of the left

ventricle (4).

1

3

22

3

4

Mean vector

Cardiac vector

Electrical Axis


The big arrow is the heart’s mean (average) electrical vector. If you averaged the millions of cardiac vectors,

you would get the “mean vector”.

1

3

22

3

4

Mean vector

Cardiac vector

Mean Electrical Vector

+

+

+ A B A

B

Mean vector moves towards positive electrode = positive QRSMean vector moves towards positive electrode = positive QRSMean vector moves away from positive electrode = negative QRSMean vector moves away from positive electrode = negative QRSMean vector is perpendicular to positive electrode = equiphasic QRSMean vector is perpendicular to positive electrode = equiphasic QRS


Red arrow is heart’s

mean electrical vector


Lead I views the heart’s

Vector similar to the

image on the left.

Leads II & III do the same

from their angles.

Einthoven’s Triangle

=

Hexaxial Reference System

The arrows and lead

names are placed on

the side of the

positive electrode.

I

IIIII


The augmented leads provide the other 3 leads of the hexaxial reference system.



I

IIIII

+

aVF

aVLaVR

=


Hexaxial Reference SystemHexaxial Reference System

QuickTime™ and ampeg4 decompressor

are needed to see this picture.


• Lead I cuts through body horizontally

• aVF cuts through body vertically• II, III, aVF are inferior• III & aVL are reciprocal


How to use it


Find the most equiphasic lead


Find the most equiphasic lead


• When the mean axis is perpendicular to the positive electrode, the QRS is equiphasic.

+

+

+ A B A

B


Find Lead I on the

reference diagram.

Find the lead

perpendicular to

Lead I


Find Lead I on the

reference diagram.

Find the lead

perpendicular to

Lead I


Look at aVF, is it positive or negative?


Since aVF is positive,

look at the measure

next to the side with

the up arrow.

Axis is about +90


About +90

Axis Determination

• Is that too much work?• You’re first time is always the hardest.• The more you do this, the easier it is to

do.• Eventually, you won’t need any

diagrams.

Axis Determination

Lets practice…

Axis Determination

Find the most equiphasic lead.

Axis Determination

Looks like Lead II…

Axis Determination

Lead aVF

Axis Determination

Which lead is

perpendicular to

aVF?

Axis Determination

Which lead is

perpendicular to

aVF?

Axis Determination

Is Lead I positive or negative?

Axis Determination

Since Lead I is

Positive, the

axis is about 0

Axis Deviation

• So what is a normal axis?

• Why does it matter if an axis is deviated?

Normal Axis

• The normal quadrant for the QRS axis is the Southeast quadrant.

• From 0 to 90

Left Axis Deviation

• From -90 to 90• This is considered the

Northeast quadrant.

Left Axis Deviation

• From 0 to -30• This is considered

physiological left axis deviation

• Pathological axis deviation is from -30 to -90

• Most common cause is left anterior fascicular block

Right Axis Deviation

• From 90 to -180• Negative QRS in Lead I • Positive QRS in aVF

– Possible Left Posterior Fascicular Block

– Q-Waves from lateral MI– Right Ventricular

Hypertrophy– Pulmonary Disease.

Extreme Right Axis Deviation

• Called ERAD• From -90 to -180• QRS in I, II, & III are negative• Probably ventricular

– Idioventricular– Paced rhythm

Cheat SheetNormal

Axis

0 to 90

Physiologic

Left

0 to -30

Pathologic

Left

-30 to -90

Right Axis

90 to 180

Extreme Right Axis

-90 to 180

Indeterminate

Axis

?

Lead I

Lead II

Lead III

Practice

Look at leads I, II, & III

Cheat SheetNormal

Axis

0 to 90

Physiologic

Left

0 to -30

Pathologic

Left

-30 to -90

Right Axis

90 to 180

Extreme Right Axis

-90 to 180

Indeterminate

Axis

?

Lead I

Lead II

Lead III

Practice

Normal Axis

Practice

Normal Axis

Practice

Which lead is equiphasic?

Practice

Which lead is equiphasic?

Practice

• Lead aVL is equiphasic

• Lead II is perpendicular to aVL

• Lead II is positive

Practice

About 60?

Quadrant Method

• Much easier to do. • Faster and more practical for rapid

interpretation. • Does not give you a very close

estimate.

Quadrant Method

ERAD LAD

RAD Normal

180 0

-90

90

Quadrant Method

ERAD LAD

RAD Normal

- I I +

aVF +

aVF -

Quadrant Method

- I I +

aVF +

aVF -

Positive QRS in Lead I

Negative QRS in Lead I

Practice

Lets take a look

Quadrant Method

- I I +

aVF +

aVF -

Quadrant Method

aVF +

- I I +

aVF -

Negative QRS Complex in aVF

Positive QRS Complex in aVF

Practice

Lets take a look

Quadrant Method

- I I +

aVF +

aVF -

Quadrant Method

- I I +

aVF +

aVF -

Quadrant Method

ERAD LAD

RAD Normal

180 0

-90

90

Quadrant Method

Lead I aVF

Normal Positive (+) Positive (+)

RAD Negative (-) Positive (+)

LAD Positive (+) Negative (-)

ERAD Negative (-) Negative (-)

Frontal Axis

Modern 12-Lead monitors do a pretty good job estimating the QRS Axis.

Frontal Axis

Precordial Axis

• Sometimes called Z axis

• Clockwise or Counterclockwise rotation

Precordial Axis

Precordial Leads = V Leads

Sometimes called Chest Leads

Precordial Axis

• The main impulse travels down then to the left.

1

3

22

3

4

Mean vector

Cardiac vector

Precordial Axis

1

3

22

3

4

Mean vector

Cardiac vector

V1 V2

V3V4 V5

V6

Precordial Axis

Lets pretend the impulse is a delivery truck that has a positive front end and a negative back end.

+-

Precordial Axis

Precordial Axis

V1 V2 V3 V4 V5 V6

Precordial Axis

V1 V2 V3 V4 V5 V6

+

Precordial Axis

V1 V2 V3 V4 V5 V6

+

Precordial Axis

V1 V2 V3 V4 V5 V6

+-

Precordial Axis

V1 V2 V3 V4 V5 V6

+-

Precordial Axis

V1 V2 V3 V4 V5 V6

+-

Precordial Axis

V1 V2 V3 V4 V5 V6

+-

Prec ordial Axis

V1 V2 V3 V4 V5 V6

+-

Precordial Axis

V1 V2 V3 V4 V5 V6

+-

Precordial Axis

• The normal transition zone is between V3 and V4.

• V1 should be predominately negative.

• V6 should be mostly positive.

Precordial Axis

Lets take a look at a 12-lead

Precordial Axis

Is V1 mostly negative?

Precordial Axis

Is V6 mostly positive?

Precordial Axis

Where is the transition?

Precordial Axis

The Precordial Axis is Normal

Precordial Axis

Now picture the precordial leads in this pattern.

V1

V2

V3

V4

V5V6

Precordial Axis

V1

V2

V3

V4

V5V6

Normal transition

Precordial Axis

V1

V2

V3

V4

V5V6

Early transition = Counterclockwise Rotation

Precordial Axis

V1

V2

V3

V4

V5V6

Late transition = Clockwise Rotation

Precordial Axis

Precordial Axis

Early Transition - Counterclockwise Rotation

Precordial Axis

Early Transition - Counterclockwise Rotation

Precordial Axis

Another Example

Precordial Axis

Late Transition - Clockwise Rotation


ERAD-90 to 180




Rotation







Fascicles

• Right Bundle Branch– 1 Fascicle

• Left Bundle Branch– 2 Fascicles

• Left Anterior• Left Posterior

Fascicular Blocks

Left AnteriorFascicular Block

Left PosteriorFascicular Block

Fascicular Block

• Bifascicular Block– Right Bundle Branch Block (RBBB) with either:

• Left Anterior Fascicular Block (LAFB)• Left Posterior Fascicular Block (LPFB)

– Only one fascicle remaining

• Trifascicular Block– RBBB with LAFB/LPFB and 1st degree AV Block– May degrade into lethal arrhythmia rapidly

Practice

Practice

Identify the rate & regularity

Practice


Practice


Practice


1 2 3

Practice


1 2 3

300 ÷ 3 = 100

Practice

Identify the rhythm

HR ≈ 100

Practice

Identify the rhythm

HR ≈ 100

Practice

Identify the rhythm

HR ≈ 100

Practice

Normal Sinus Rhythm

HR ≈ 100

Normal Sinus

Practice

Frontal Axis?

HR ≈ 100

Normal Sinus

Practice

Frontal Axis?

HR ≈ 100

Normal Sinus

Practice

Frontal Axis?

HR ≈ 100

Normal Sinus

Practice

• Equiphasic lead is aVF.

• Find lead perpendicular to aVF

Practice

• Equiphasic lead is aVF.

• Find lead perpendicular to aVF

Practice

Frontal Axis?

HR ≈ 100

Normal Sinus

Practice

• Lead I is positive

• Frontal axis is about 0

Practice

• Lead I is positive

• Frontal axis is about 0

• That is in normal quadrant.

Practice

Frontal Axis = Normal, about 0

HR ≈ 100

Normal Sinus

Frontal axis is normal

Practice

Precordial Axis

HR ≈ 100

Normal Sinus


Practice

Early Transition, Counterclockwise Rotation

HR ≈ 100

Normal Sinus


Practice

Lets try another

Practice

Practice

Determine Rate & Rhythm

Practice

Determine Rate & Rhythm

HR ≈ 75

Normal Sinus

Practice

Determine Frontal Axis

HR ≈ 75

Normal Sinus

Quadrant Method

ERAD LAD

RAD Normal

180 0

-90

90

Practice


HR ≈ 75

Normal Sinus

Quadrant Method

Lead I aVF

Normal Positive (+) Positive (+)

RAD Negative (-) Positive (+)

LAD Positive (+) Negative (-)

ERAD Negative (-) Negative (-)

Cheat SheetNormal

Axis

0 to 90

Physiologic

Left

0 to -30

Pathologic

Left

-30 to -90

Right Axis

90 to 180

Extreme Right Axis

-90 to 180

Indeterminate

Axis

?

Lead I

Lead II

Lead III

Practice


HR ≈ 75

Normal Sinus

Practice

Determine Precordial Axis

HR ≈ 75

Normal Sinus

Pathological Left Axis

Precordial Axis

V1

V2

V3

V4

V5V6

Early transition = Counterclockwise Rotation

Practice

Determine Precordial Axis

HR ≈ 75

Normal Sinus

Pathological Left Axis

Counterclockwise Z


ERAD-90 to 180




Rotation







Lesson Two

“Its finally over”

…Well almost.

More to come in lesson three.

Business

12 lead-lesson 2