• Normal Axis
• Right Axis Deviation (RAD)
• Left Axis Deviation (LAD)
• Atrial Hypertrophy (enlargement)
• Ventricular Hypertrophy

Axis

What does “axis” mean?

Direction of the movement of depolarization

Determined by:

anatomic cardiac position

direction of ventricular depolarization

Vectors:

mean QRS vector = sum of all depolarization vectors

Review! Hexaxial Diagram

Know degrees for all 6 leads in the frontal plane!

Calculation of Axis

Dubin's way:

Find the isoelectric complex in the extremity leads

the mean QRS axis is directed 90° from that lead!

Calculation of Axis (another way!)

Use graph paper

Look at lead I and AVF

Graph “net” positivity or negativity for both I and AVF

subract (+) from (-) = net

Draw perpendicular lines from each point

QRS axis intersects!

Normal Axis

Dubin says: 0° to +90°

So, use this range for examinationpurposes.

Dubins 'double thumbs up sign! Both Lead I and Lead AVF are POSITIVE!

(Other sources may say…-30°to +100°)

Right Axis Deviation

+90° to - 90° axis deviation

+180° to -90° considered extreme and unusual!

Lead I and AVF mostly negative: No man’s land!

Lead I mostly (-), lead AVF mostly (+): RAD

causes: right ventricular hypertrophy, left wall MI, left posterior hemiblock, chronic lung disease, slender/tall

Left Axis Deviation

0° to -90° axis deviation

Lead I (+)

Lead AVF (-)

causes: left ventricular hypertrophy, left anterior hemiblock, left bundle branch block, obesity

Hypertrophy

Cardiac enlargement or dilation of heart chamber

heart muscle stretched or chamber enlarged

hypertrophy of heart muscle

heart muscle fibers increase in size

chamber enlarged

chronic pressure or volume load on heart muscle

Right and Left Atrial Hypertrophy

RAH

Diphasic P waves in V1 with initial portion dominant

TALL: > 2.5 mm high

Cause: right ventricular hypertrophy, pulmonary disease, pulmonic valve stenosis

Overload of right atrium increases voltage of ‘P’ wave

LAH

Diphasic or notched ‘P’ waves in V1 with second portion dominant

WIDE: > 0.12 sec (> 3 small boxes)

Cause: hypertension, valvular disease, CAD, cardiomyopathies

Prolong total duration of atrial depolarization; therefore wide ‘P’ wave

Right Ventricular Hypertrophy

QRS V1

Characteristics

large ‘R’ waves V1

Progressively gets smaller toward left chest leads

V1>V6

Cause: congenital heart disease, valvular stenosis, emphysema

Left Ventricular Hypertrophy

QRS in chest leads

Right V1 and V2

Left V5 and V6

Characteristics

S in V1 + R in V5 > 35 mm TALL!

LV strain pattern= T wave inversion and/or ST depression

Cause: valvular heart disease, systemic hypertension, CHF, cardiomyopathies

Pressure or volume overload state