Graphical abstract image. Burden of scar in the basal septum assessed using late gadolinium enhancement (LGE) predicts failure of the lead to penetrate the septum deep enough to reach the left bundle area. Middle figure shows two cardiac MRI images of the basal septum with LGE left; no scar and right high scar burden (white color). Once the lead is advanced there is no correlation between the paced QRS duration and basal septal scar burden.