B-po01-022 exploring the optimal pacing modality in patients with high-grade atrioventricular block and right bundle branch block pattern: a pilot study

For patients with right bundle branch block (RBBB) pattern in ECG who need a high percentage of ventricular pacing, biventricular pacing showed limited benefits. To explore the optimal pacing modality in high-degree atrioventricular (AV) block and RBBB pattern. We assessed the feasibility and outcomes of different pacing approach in consecutive patients with high-degree AV block and RBBB pattern from July 2018 to Jan 2021. Trans-septal pacing was attempted in 51 patients (34 men, age 73±11 years) by capturing 1) His-bundle (HBP) (n=8); 2) left bundle branch (LBBP) (n=25); and 3) para-Hisian interventricular septum (IVS pacing) (n=18). The baseline QRS duration (QRSd) was 144±17ms, with no significant difference between groups. HBP could not correct the RBBB with an acceptable threshold and was abandoned for permanent pacing in 4 out of 8 cases. IVS pacing led to varied QRS configurations with the QRSd of 133±14 ms and the left ventricular activation time (LVAT) of 87±13 ms. Isolated LBBP (LBBPiso) produced an RBBB pattern with a QRSd of 124±13 ms (p<0.001 vs. the intrinsic, and p=0.049 vs. IVS pacing) and LVAT of 75±11 ms (p=0.004 vs. IVS pacing). When optimized with AV delay or bipolar setting, further reduced QRSd of 112±14 ms (p<0.001 vs. LBBPiso) and fading of RBBB was achieved. The pacing thresholds of LBBP decreased further during follow-up (0.6±0.2V/0.4ms vs. 0.8±0.2 V/0.4ms at implantation, p=0.009). In patients with high-degree AV block and RBBB pattern, LBBP combined with programmed optimization retained most electrical synchrony with satisfactory safety and might serve as a preferred pacing modality.