In left anterior fascicular block (LAFB), impulses are conducted to the left ventricle via the posterior fascicle, producing characteristic ECG changes
Trifascicular block (TFB) refers to the presence of conducting disease in all three fascicles: RBBB, LAFB, LPFB. LITFL ECG Library
Bifascicular block is the combination of RBBB with either LAFB or LPFB. Conduction to the ventricles is via the single remaining fascicle.