Figure 2 (A) Atrial fibrillation with ventricular aberration resulting from the Ashman phenomenon, and probably concealed transseptal conduction. After a long pause (*) the refractory period of the left bundle branch is prolonged which results in 10 RS complexes with left bundle branch block morphology. The aberration is probably perpetuated by concealed transseptal conduction (“linking phenomenon”) from the right into the left bundle with block of antegrade conduction of the subsequent impulses in the left bundle. (B) The solid line represents the His bundle; the dashes (dots) represent the left (right) bundle. The solid horizontal bars represent the refractory period.