Background: His bundle pacing (HBP) has been shown to overcome right bundle branch block (RBBB). RBBB + left anterior fascicular block (LAFB) and RBBB + left posterior fascicular block (LPFB) correction with HBP remains unclear.
Objective: To demonstrate that conduction system capture can overcome RBBB & RBBB + fascicular block.
Methods: Nine patients with RBBB and fascicular block (7 pts RBBB + LAFB; 2 pts RBBB + LPFB) underwent electro-anatomical mapping (EAM) and/or permanent HBP. Pace mapping with a quadripolar catheter to achieve RBBB and LAFB/LPFB correction was performed. Sites resulting in normalization of RBBB and electrical axis were tagged.
Results: RBBB pattern and electrical axis were normalized in 2/9 with selective (S)-HBP and in 9/9 pts with nonselective (NS)-HBP. NS-HBP correction sites were distal, S-HBP were proximal. Both were proximal to RB signal and/or capture. Sites of S-HBP did not correct RBBB in 7/9 pts. H-QRS_end interval was 216 ± 25 ms at baseline. HBP and septal ventricular pacing shortened Stim-QRS_end. Catheter induced PVCs also corrected electrical axis, suggesting that septal depolarization rather than conduction system recruitment may be responsible. Figure A: twelve lead ECG shows S-HBP with (first 2 beats) and without (3rd, 4th beats) correction of RBBB/LAFB. Figure B: baseline RBBB/LAFB (inset) and distal NS-HBP with correction of RBBB/LAFB
Conclusion: 1. Distal NS-HBP can normalize RBBB pattern and electrical axis. Septal muscular capture may be responsible for this 2. S-HBP with inherent conduction system recruitment can also result in correction of RBBB and fascicular blocks 3. Definitive proof of fascicular recruitment will require further studies.