LAFB, a.k.a: L. ant. hemiblock:
QRS 90 - 100 msec or normal
Left axis deviation (r/o other causes - COPD, inf. MI, LVH) more neg than -45 degrees
rS complexes in II, III, aVF
q wave in I and/or aVL
LPFB, a.k.a - L. post. hemiblock:
RAD (r/o other causes: RVH, COPD, lat. MI, RBBB). Axis >110 degrees
narrow QRS <120 msec
rS wave in I, aVL
Leads II, III, aVF:
narrow QRS
qR wave
Pattern: rS in I, aVL; qR in II III, aVF.