Role of Peri-deployment Right Ventricular Paced-ECG in Left Bundle Area Pacing

Wen-De Tang¹Chiung-Ray Lu¹Mei-Yao Wu¹Ching-Fen Chang¹Yin-Huei Chen¹Hung-Pin Wu¹Hei-Tung Yip²Kuan-Cheng Chang¹Yen-Nien Lin^1*

• ¹China Medical University Hospital, Taichung, Taiwan
• ²China Medical University (Taiwan), Taichung, Taiwan

Background: Left bundle area pacing (LBBAP) has emerged as a promising physiological pacing modality. The current technique for LBBAP lead implantation predominantly relies on the anatomy of His bundle and right ventricular septum. While practical, this anatomical approach can lead to variations in lead polarities and QRS durations due to extensive target zone. Objectives: This study aims to investigate whether peri-deployment paced ECGs can guide LBBAP and enhance left ventricular activation. We conducted a retrospective analysis of 41 patients (54 attempts) who underwent LBBAP. QRS patterns were categorized into five types: R,Rs,rs,rS, and S, and were labeled from 1 to 5 for polarity analysis. Results: LBBAP was successfully achieved in 81.5% of the attempts. During the procedure, the paced QRS duration (QRSd) significantly decreased from 144.5 ± 22.6 ms to 128.8 ± 22.9 ms (p < 0.001). When comparing lead polarity scores before and after deployment, there was a significant increase in leads I and aVL (p = 0.002), while leads III and aVF showed a decrease (lead III: 3.9 ± 1.2 vs 3.4 ± 1.5, p = 0.001; lead aVF: 3.1 ± 1.2 vs 2.9 ± 1.3, p = 0.026).The polarity of leads II and aVR remained unchanged. The lead polarity scores were significantly higher in leads I and aVL and lower in leads III and aVF (p < 0.001). This group also had a significantly shorter left ventricular activation time (LVAT) (68.7 ± 13.0 ms vs 98.4 ± 14.0 ms, p < 0.001). Univariate analysis revealed that a shorter pre-deployment paced QRSd and LVAT were associated with a narrower post-deployment QRSd. Additionally, non-electrical factors such as female gender and LV dilation were associated with higher post-deployment QRSd. Our study demonstrated that peri-deployment ECG assessment is a practical adjunct to anatomy-based LBBAP, providing real-time markers for optimal lead positioning. Specifically, an unaltered lead II axis and anticipated changes in the lead I/aVL and lead III/aVF axes can help guide the selection of the left bundle branch. Lower pre-deployment paced QRSd and LVAT, as well as a more rightward inferior axis after deployment, are associated with a shorter post-deployment QRSd.