[Improvement and normalisation of the QRS complex by stimulation of the bundle of His in complete left branch block].

The asynchronism of ventricular activation resulting from a major degree of left bundle branch block (QRS greater than or equal to 0.12 s) may be suppressed by stimulation of the distal portion of the His Bundle, whether the block be intermittent (3 cases) or permanent (17 cases). The selective stimulation of the His Bundle normalises ventricular depolarisation whilst non-selective stimulation narrows the QRS complex by the fusion of the activation wave fronts from the His Bundle and the interventricular septum. The reestablishment of synchronous ventricular conduction by His Bundle stimulation is generally interpreted as a sign of longitudinal dissociation in the proximal portion of the His Bundle. This results does not, however, exclude the possibility of a very localised lesion at the origin of the left bundle, responsible for a conduction delay, and suppressed by stimulation carried out close to the zone of block (summation effect, electrotonic influence).