Assessment of left ventricular dyssynchrony in pacing-induced left bundle branch block compared with intrinsic left bundle branch block

Right ventricular-pacing results in less early basal activation and more often early mid-septal and late lateral wall activation in comparison with intrinsic LBBB. Imaging techniques that only visualize the basal- or mid-part of the LV may result in a serious underestimation of dyssynchrony in patients with pacing-induced LBBB.