Normal activation of the<unk>  ventricle (LV) proceeds down the<unk>  bundle branch, which consist of three fascicles, the<unk><unk>  fascicle, the<unk>  posterior fascicle, and the septal fascicle. The posterior fascicle supplies the posterior and inferoposterior walls of the LV, the<unk>  fascicle supplies the upper and<unk>  parts of the LV and the septal fascicle supplies the septal wall with innervation.<unk>  — which is also known as<unk><unk>  hemiblock (LAHB) — occurs when a cardiac impulse spreads first through the<unk>  posterior fascicle, causing a delay in activation of the<unk>  and upper parts of the LV. Although there is a delay or block in activation of the<unk><unk>  fascicle there is still preservation of initial<unk>  to right septal activation as well as preservation of the inferior activation of the LV (preservation, on the EKG, of septal Q waves in I and aVL and predominantly negative QRS complex in leads II, III, and aVF). The delayed and unopposed activation of the remainder of the LV now results in a shift in the QRS axis<unk> ward and superiorly, causing marked<unk>  axis deviation. This delayed activation also results in a widening of the QRS complex, although not to the extent of a complete LBBB.
Left anterior fascicular block
Left posterior fascicular block
Bundle branch block
Intraventricular block
Left atrial appendage occlusion
Pre-excitation syndrome
Left bundle branch block
Sinoatrial arrest