Barriers against left bundle branch area pacing, myocardial or electrical disease: what is the matter?
Authors: Briongos Figuero S , Estevez Paniagua A , Sanchez Hernandez A , Munoz-Aguilera RT 
Published: May 2022

Funding Acknowledgements

Type of funding sources: None.

Background

Conduction system pacing via left bundle branch area pacing (LBBAP) can provide physiologic pacing by capturing the LBB (LBBP) or the deep left ventricular septal (LVS) myocardium. Several criteria can distinguish between both types of LBBAP.

Methods

Prospective study of consecutive patients who received LBBAP device for bradycardia or heart failure indications (bailed-out strategy).

LBBP was defined if monopolar paced QRS had a right bundle branch conduction delay pattern, at least one of the following criteria:

(a) Demonstration of LB potential with LB-local ventricular electrogram interval of 20–35 ms.

(b) Demonstration of transition in QRS morphology from NSLBBP to SLBB P capture or NSLBBP to LVS capture (sudden decrease in LVAT of 10 ms) with decrementing output.

(c) Peak LV activation time as measured in leads V5–V6 &lt;80 ms.

We tried to determine the influence that QRS width and LVEF have on the final paced morphology (LBBP or LVS) achieved, during LBBAP.

Results

A total of 149 patients (77 males) were included at our institution. LBBAP was achieved in 145 patients (97.3%). Mean age was 79.2±9.2 years, QRS width was 119.3±19.5 ms, a narrow (&lt; 120 ms) QRS complex was present in 77 patients (51,7%) and LVEF ≤ 40% in 16 (10,7%). Indications for pacing were complete AV block (n=30), degree AV block (n=25), slow AF (n=21), bifascicular or trifascicular block (n=11), sinus node disease or bradi-tachy syndrome (n=55) and need for resynchronization therapy (n=6). A Medtronic 3830-69 lead was implanted using a C-315-His sheath in all procedures. His mapping was not perfomed to select the target delivery zone.

Overall, paced QRS duration after LBBAP was 115.6±14.8 ms. LBBP was achieved in 112 patients (NSLBBP in 63 and SLBBP in 49) while LVS was achieved in the remaining 30 patients. Left bundle potential was seen in 62 patients (41.6%) and mean LVAT (measured at V5/V6) was 80.1±11.3 ms.

As seen in table 1, LBBP was less often achieved among wide QRS patients compared to narrow QRS patients. Moreover, left bundle potential appeared less frequently and, paced QRS duration and LVAT were more prolonged, despite the significant reduction in QRS duration observed among wide QRS complex patients.

Paced QRS duration after LBBAP was longer among patients with LVEF≤40% compared to patients with LVEF&gt;40%, and LBBP was also more difficult to achieve (table 2).

We specifically analyzed the subgroup of patients with wide QRS complex (n=72). LBBP among those with LVEF≤40% (n=12) was only achieved in 54.5% compared to patients with LVEF&gt;40% (71.4%). Paced QRS duration (130.9±13.6 vs 119±15.1; p=0.002) and LVAT were also longer (92.3± 8.7 ± 81.3±11.1; p=0.020).

Conclusions

Electrical delay and myocardial disease represent two barriers to achieve LBBP. The combination of both conditions might select a subgroup of patients in which LBBAP supposes a challenge.