This delayed activation also results in a widening of the QRS complex, although not to the extent of a complete LBBB.

[citation needed] LAFB cannot be diagnosed when a prior inferior wall myocardial infarction (IMI) is evident on the ECG.

IMI can also cause extreme left-axis deviation, but will manifest with Q-waves in the inferior leads II, III, and aVF.

By contrast, QRS complexes in the inferior leads should begin with r-waves in LAFB.

It also makes the electrocardiographic diagnosis of LVH more complicated, because both may cause a large R wave in lead aVL.