Determining AXIS: 12 Lead
ECG's
Using the Hexaxial Diagram to find the degree of Axis
Deviation
This technique is a little hard to learn
but it is very accurate (+ or – 100 to 150)
Emily Koch, RN, BSN, ACNPc
Clinician III
4 East UVA Health System
Basics of 12 Lead ECG's
Determining AXIS
M arked RA D
-90°
To determine the axis
a scale must be used
such as the one at the
left. Each physician
uses a slightly
different degree as the
upper limit of normal,
but typically 105-110
degrees.
-60°
-120°
LA D
aV R
-30°
-150°
aV L
0°
180°
I
150°
30°
120°
60°
III
90° aV F
RA D
II
N orm al A xis
-30° to +100°
Basics of 12 Lead ECG's
Determining AXIS
M arked RA D
-90°
-60°
-120°
First you must find the most
equiphasic QRS complex in
the six limb leads. This is
done by adding and
subtracting the number of
squares each QRS complex
has above the baseline and
below the baseline in each
lead.
LA D
aV R
-30°
-150°
aV L
0°
180°
I
150°
30°
120°
60°
III
90° aV F
RA D
II
N orm al A xis
-30° to +100°
Basics of 12 Lead ECG's
Determining AXIS
Locate the lead
perpendicular to the lead
with the most isoelectric
QRS. If the perpendicular
lead has a positive QRS,
orient the axis to the
positive pole of this lead. If
it is negative then
orient it to the negative
Pole of this lead.
Basics of 12 Lead ECG's
Determining AXIS
If there is a lead with a QRS
that is taller than the lead
perpendicular to the most
isoelectric, the axis is the
mean of the two.
Remember: If the tallest
lead has a positive QRS,
orient the axis to the
positive pole of this lead. If it
is negative then
orient it to the negative
pole.
Causes of Abnormal Axis
Left Axis Deviation = An axis between -30 and -90
 May be normal in the elderly and very obese
 Due to high diaphragm during pregnancy, ascites, or ABD
tumors
 Left Anterior Hemiblock
 Left Bundle Branch Block
 WPW Syndrome
 Congenital Lesions
 Right Vent. Pacer or ectopic rhythms
 Emphysema
Causes of Abnormal Axis
Right Axis Deviation = An axis between +120 and
+180
 Can be normal variant
 Right Vent. Hypertrophy
 Right Bundle Branch Block
 Left Posterior Hemiblock
 Left Ventricular ectopic rhythms
 Some right Vent. Ectopic rhythms
 WPW Syndrome
Causes of Abnormal Axis
Extreme Right Axis Deviation = An axis between 90 and +180
 Ventricular ectopic rhythms
 Right Vent. Paced rhythms
 Less commonly seen in patients with
cardiomyopathies and in those with multiple
MI's
Normal ECG
Determine Axis