IMI can also cause extreme left-axis deviation, but will manifest with Q-waves in the inferior leads II, III, and aVF. LAFB cannot be diagnosed when a prior inferior wall myocardial infarction (IMI) is evident on the ECG.

Delayed intrinsicoid deflection in lead aVL (> 0.045 s).

rS pattern (small r, deep S) in the inferior leads II, III, and aVF.

qR pattern (small q, tall R) in the lateral limb leads I and aVL.

Abnormal left axis deviation (usually between –45° and –60°).

This delayed activation also results in a widening of the QRS complex, although not to the extent of a complete LBBB. The delayed and unopposed activation of the remainder of the LV now results in a shift in the QRS axis leftward and superiorly, causing marked left axis deviation.

Although there is a delay or block in activation of the left anterior fascicle there is still preservation of initial left 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). LAFB - which is also known as left anterior hemiblock (LAHB) - occurs when a cardiac impulse spreads first through the left posterior fascicle, causing a delay in activation of the anterior and upper parts of the LV. The posterior fascicle supplies the posterior and inferoposterior walls of the LV, the anterior fascicle supplies the upper and anterior parts of the LV and the septal fascicle supplies the septal wall with innervation.

Normal activation of the left ventricle (LV) proceeds down the left bundle branch, which consist of three fascicles, the left anterior fascicle, the left posterior fascicle, and the septal fascicle. 2.1 Effects of LAFB on Diagnosing Infarctions and Left Ventricular Hypertrophy.

Ivcd with lad