
Class, Below is an example how to determine the QRS axis and degrees when Lead I is the Biphasic (close to isoelectic) Lead 

STEP 1: Is the QRS in Lead I mostly positive or negative? LEAD I is the Biphasic Lead (closest to isoelectric) 
STEP 2: Is the QRS in AVF mostly positive or negative? POSITIVE 
STEP 3: Which lead is the biphasic lead closest to isoelectric. Lead I 
REMINDER: THE MEAN QRS AXIS IS ALWAYS PERPENTICULAR TO THE BIPHASIC LEAD. AND, STEP 1 AND STEP 2 HAVE IDENTIFIED THE QUADRANT OF THE MEAN QRS 
STEP 4: Determine QRS Axis and degrees? Since Lead I is the biphasic lead and AVF is positive, the classification is Normal Axis +90 Degrees 

Class, Below is an example how to determine the QRS axis and degrees when AVF is the Biphasic (close to isoelectic) Lead 

STEP 1: Is the QRS in Lead I mostly positive or negative? LEAD I is mostly positive 
STEP 2: Is the QRS in AVF mostly positive or negative? AVF is the Biphasic lead closest to isoelectric 
STEP 3: Which lead is the biphasic lead closest to isoelectric. AVF 
REMINDER: THE MEAN QRS AXIS IS ALWAYS PERPENTICULAR TO THE BIPHASIC LEAD. AND, STEP 1 AND STEP 2 HAVE IDENTIFIED THE QUADRANT OF THE MEAN QRS 
STEP 4: Determine QRS Axis and degrees? Since AVF is the biphasic lead and Lead I is positive, the classification is Normal Axis 0 Degrees 

Review: Mean QRS Axis Classification Quadrants


Normal Axis: from 30 degrees to +100 degrees 
Right Axis Deviation: from +100 degrees to ±180 degrees 
Extreme Right Axis Deviation: from ±180 degrees to 90 degrees 
Left Axis Deviation: from 90 degrees to 30 degrees 

