 ### Description

The electrical axis for the QRS complex in the frontal (coronal plane) can be determined from the standard limb leads (I, II, III, aVF, aVL, aVR). Change in the electrical axis in the frontal plane is referred to as axis deviation.

Conventions:

(1) sagittal midline caudal (inferior): +90°

(2) patient's left side in frontal (coronal) plane: 0°

I

II

III

aVL

aVF

aVR

Axis in Degrees

N

N

P

N

I

P

-180 (+180)

N

N

P

N

N

P

-151 to -179 (+181 to +209)

N

N

I

N

N

P

-150 (+210)

N

N

N

N

N

P

-121 to -149 (+211 to +239)

N

N

N

I

N

P

-120 (+240)

N

N

N

P

N

P

-91 to -119 (+241 to +269)

I

N

N

P

N

P

-90 (+270)

P

N

N

P

N

P

-61 to -89

P

N

N

P

N

I

-60

P

N

N

P

N

N

-31 to -59

P

I

N

P

N

N

-30

P

P

N

P

N

N

-1 to -29

P

P

N

P

I

N

0

P

P

N

P

P

N

1 to +29

P

P

I

P

P

N

+30

P

P

P

P

P

N

+31 to +59

P

P

P

I

P

N

+60

P

P

P

N

P

N

+61 to +89

I

P

P

N

P

N

+90

N

P

P

N

P

N

+91 to +119

N

P

P

N

P

I

+120

N

P

P

N

P

P

+121 to +149

N

I

P

N

P

P

+150

N

N

P

N

P

P

+151 to +179

N

N

P

N

I

P

+180

where:

• N = complex predominantly negative

• I = isoelectric = equally positive and negative = axis is perpendicular to that lead

• P = complex predominantly positive

Using subgroups in table to find the axis:

(1) first use I and aVF to determine quadrant (0 to +90°, +90 to +180°, 0 to -90°, -90 to -180°)

(2) if patient's lower left quadrant (0 to +90°): look at III and aVL

(3) if patient's lower right quadrant (+90 to +180°): look at II and aVR

(4) if patient's upper left quadrant (0 to -90°): look at II and aVR

(5) if patient's upper right quadrant (-90 to -180°, +180 to +270°): look at III and aVL

Interpretation

Axis

Interpretation

-30 to +90°

normal

+90 to +/- 180°

right axis deviation

-30 to -90°

left axis deviation

-90 to -180 (+180 to +270)

extreme axis deviation