Exam
QRS Axis
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QRS Axis
, EKG Axis, Electrocardiogram Axis
See Also
Electrocardiogram
Cardiac Electrophysiology Anatomy
Left Axis Deviation
Right Axis Deviation
Interpretation
Axis Determination (Method 1)
Images: EKG Axis
Check lead I (0 degrees)
QRS positive (predominately up)
Vector points to patient's Left
Correlates with right half of axis circle (12:00 to 6:00 on clockface)
QRS negative (predominately down)
Vector points to patient's Right (6:00 to 12:00 on clockface)
Correlates with left half of axis circle (always
Right Axis Deviation
)
Check lead aVF (90 degrees)
QRS positive (predominately up)
Vector points to bottom half of axis circle (3:00 to 9:00 on clockface)
QRS negative (predominately down)
Vector points to upper half of axis circle (
Left Axis Deviation
if -30 to -90 degrees, or 12:00 to 2:00)
Interpretation
Indeterminate:
Extreme Right Axis Deviation
Lead I: Negative QRS
Lead aVF: Negative QRS
Right Axis Deviation
Lead I: Negative QRS
Lead aVF: Positive QRS
Normal range
Lead I: Positive QRS
Lead aVF: Positive QRS
Left Axis Deviation
Lead I: Positive QRS
Lead aVF: Negative QRS (normal if -30 to 0 degrees, 2:00 to 3:00 on clockface)
Interpretation
Axis Determination (Method 2)
Select Isoelectric lead from limb and augmented leads
Isoelectric lead averages to baseline
Positive deflection equals negative deflection
Identify isoelectric lead on axis circle
Lead with most symmetric voltage (as much positive QRS voltage as negative QRS voltage)
Choose lead that is perpendicular to isoelectric lead
Use Lead I and aVF to determine quadrant
Read perpendicular lead's degrees off axis circle
Extreme Right Axis Deviation
(-90 to -180, negative in lead I and negative in lead avF)
Most Isoelectric I (avF is perpendicular): -90 (12:00)
Most Isoelectric avL (II is perpendicular): -120 (11:00)
Most Isoelectric III (avR is perpendicular): -150 (10:00)
Most Isoelectric avF (I is perpendicular): -180 (9:00)
Right Axis Deviation
(+180 to +90, negative in lead I and positive in lead avF)
Most Isoelectric avF (I is perpendicular): +180 (9:00)
Most Isoelectric II (avL is perpendicular): +150 (8:00)
Most Isoelectric avR (III is perpendicular): +120 (7:00)
Most Isoelectric I (avF is perpendicular): +90 (6:00)
Left Axis Deviation
(-90 to -30, positive in lead I and negative in lead avF)
Most Isoelectric I (avF is perpendicular): -90 (12:00)
Most Isoelectric avR (III is perpendicular): -60 (1:00)
Most Isoelectric II (avL is perpendicular): -30 (2:00)
Normal Axis (+90 to -30, positive in lead I and positive in lead avF)
Most Isoelectric avF (I is perpendicular): 0 (3:00)
Most Isoelectric III (avR is perpendicular): +30 (4:00)
Most Isoelectric avL (II is perpendicular): +60 (5:00)
Most Isoelectric I (avF is perpendicular): +90 (6:00)
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