<div>Analysis by patient groups</div><div>NS-S Group:</div><div>Acute RBBB=6, Chronic RBBB=11.</div><div>These patients transitioned from NS-HBP to S-HBP at a mean pacing
voltage of 2.4±0.8V (capture threshold of NS-HBP). The capture threshold
of S-HBP was 1.0±0.7 V.</div><div>The baseline H-V interval was 53±8 ms. Following transition to S-HBP the
stim-q interval was 57±10 ms.</div><div>In patients who developed acute RBBB with active fixation, the RBBB was
completely reversed with NS-HBP phase (from 5.0V to &gt;
2.4±0.8V), however upon transition to S-HBP phase complete RBBB recurred
in all patients in this group (Fig. 1).</div><div>In patients with chronic RBBB, either partial (8/11) or complete
correction of RBBB (3/11 patients) occurred but only during the NS-HBP
phase at pacing voltage &gt; 2.4±0.8V. Like acute RBBB, in all
11 patients with chronic RBBB recurred on transition to S-HBP phase
(Figures 2,3).</div><div>Of the 9 patients with complete correction of RBBB, in 2 patients with
acute RBBB and 1 patient with chronic RBBB as pacing voltage was
lowered, a progressive increase in rightward delay was seen (Figs. 1,4).
This voltage effect was seen only with NS-HBP and not during S-HBP where
abrupt recurrence of complete RBBB was seen in all patients.</div><div>Figure1: Effect of NS-HBP and S-HBP in acute RBBB</div>