A (+) aVF means the axis is
0 to 180
A (+) lead I means the axis is
90 to (-)90
Leads used to assess QRS axis
I and aVF
The tallest QRS in the frontal plane
The axis is in this direction
Frontal: I, II, III, aVR, aVF
An equiphasic QRS complex
The axis is perpendicular to that lead Find a (+) lead which is perpendicular, it points in that direction
Hexaxial reference
I=aVF
45
Hexaxial reference system
I>aVF
0 to 45
Hexaxial reference system
aVF>I
45 to 90
Normal p wave axis
0-75
Normal t wave axis
close to QRS axis
R wave in Lead II > R wave in aVF
The axis is
Normal
Strong left axis deviation
R wave in aVL>I
Strong right axis deviation
R wave in III>aVF
biphasic p wave in
V1
Assess atrial enlargement in leads
II and V1
RAE criteria
Amplitude >2.5 mm
Initial component of P wave in a biphasic V1 is larger t
LAE criteria
Duration >.10 secs
Terminal portion of P wave in V1 is negative with a duration of >.04 and depth >1 mm
Often associated with notched P wave on Lead II→ not sufficient for diagnosis alone
LVH criteria
- Sum of deepest S in V1/V2 plus tallest R V5/V6 = >35 mm
- R in aVL > 11 mm
- R in Lead I plus S in Lead II = >25 mm
RVH criteria
- Right axis deviation > +90
- R wave > S wave in V1
→ R wave usually > 7 mm - S wave > R wave in V6
