Automatic Threshold Function With Left Bundle Branch Area Versus Traditional Right Ventricular Lead Placement.

Introduction: Left bundle branch area pacing (LBBAP) leverages the strengths of His bundle pacing (HBP) and traditional myocardial pacing. While automatic threshold (AT) algorithms are often not suitable for HBP leads, their function in LBBAP remains uncertain.

Methods: Data from the LATITUDE remote monitoring system were evaluated retrospectively comparing LBBAP leads to a sample of right ventricular (RV) placed leads. AT accuracy was assessed comparing the nearest in-office (IO) pacing capture threshold (PCT) ± 7 days at 1 and/or 3 months at 0.4 ms pulse width. Methodology from a previous trial (CAPTIVATE, NCT02097290) used for regulatory approval of an AT algorithm for standard RV apical leads was employed, comparing percent of accurate tests, with an accurate test defined as: |AT - IO | ≤ 0.6 V (or ≤ 1 V if IO > 3.5 V). Secondary analysis assessed the percentage of devices with AT turned off during 6 mo follow-up. Statistical comparisons were made using Chi-square tests.

Results: Data from 1288 devices (798 LBBAP, 490 RV) were evaluated, limited by the in-office visit requirement for comparison. Among LBBAP patients, 677 had an INGEVITY+ lead, 121 FINELINE II. Generators were 668 PM, 128 CRT-D/P, 2 ICD; 694 in RV port, 96 LV, 8 RA. Compared to IO PCT, the AT algorithm accuracy was 96.9% in LBBAP leads and 97.6% in RV leads, (LBBAP vs. RV p = 0.47, Figure 1), both exceeding the 90% target. The median (IQR) difference between AT and IO PCTs for LBBAP leads was 0.1 V (0.0, 0.2 V); 59%, 81% and 91% of AT values were within 0.1, 0.2 and 0.3 V of IO, respectively (Figure 2). The AT feature was turned off at similar rates for LBBAP and RV leads in first 6 mo (LBBA 1.8%, RV 0.9%; p = 0.18; Figure 3).

Conclusion: AT algorithms' accuracy was high and similar for RV and LBBAP leads in this analysis. Future research is needed to determine if current algorithms are sufficient for achieving conduction system capture when the conduction system threshold is greater than the myocardial threshold.