Conduction abnormalities

Left anterior fascicular block

ECG criteria

Left axis deviation (-45 to -90), qR in I and aVL, rS in II/III/aVF.

Related: conduction abnormalities

1st degree AV block
PR interval >200 ms, every P followed by QRS.
2nd degree AV block Mobitz I (Wenckebach)
Progressive PR prolongation until a non-conducted P wave.
2nd degree AV block Mobitz II
Constant PR with intermittent non-conducted P waves; often wide QRS.
Complete AV block
Atrial and ventricular activity completely dissociated.
Right bundle branch block
QRS ≥120 ms, rsR' in V1-V2, wide S in I and V6.
Left bundle branch block
QRS ≥120 ms, broad monophasic R in I, V5-V6, deep S in V1-V2.