Hemiblock of the LV human conduction system. (A) Knockout of the LV anterior branch resulted in the late activation of the LV basal free wall, moving the positive pole in body surface potentials from the left hip to the centre of the back, and recovering the clinical manifestations of left anterior fascicular block (LAFB). (B) Similarly, LV posterior wall stimulation knockout resulted in delayed LV basal paraseptal activation, affecting the time course and position of the negative pole in the front of the torso, with the associated clinical manifestations of left posterior fascicular block (LPFB). Representative ECGs of LAFB and LPFB are reproduced with permission from Elizari et al.9 ECG grid resolutions: 40 ms/0.1 mV (simulation); 200 ms/0.5 mV (clinical).
