SPC365

Predictors of QRS narrowing and of electrical response after left bundle branch pacing

Session: Sessão de Posters 01 - Estimulação do sistema de condução: LBBAP na prática
Speaker: Fernando Nascimento Ferreira

Congress: CPC 2026
Topic: C. Arrhythmias and Device Therapy
Theme: 09. Device Therapy
Subtheme: 09.1 Antibradycardia Pacing
Session Type: Posters Eletrónicos
FP Number: ---
Authors: Fernando Nascimento Ferreira; Sofia Jacinto; Margarida Figueiredo; Cátia Guerra; Helder Santos; Guilherme Portugal; Bruno Valente; Ana Lousinha; Paulo Osório; Pedro Silva Cunha; Rui Cruz Ferreira; Mário Oliveira

<p style="text-align:justify"><span style="font-size:medium"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="color:#000000"><strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Background: </span></span></strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Left bundle branch area pacing (LBBAP) has emerged as a physiologic pacing strategy that preserves synchronous ventricular activation and may overcome the dyssynchrony associated with conventional pacing. However, predictors of electrical response, particularly QRS narrowing, remain insufficiently characterized in real-world populations.</span></span></span></span></span></p>

<p style="text-align:justify"><span style="font-size:medium"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="color:#000000"><strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Objective: </span></span></strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Describe clinical and procedural characteristics of patients undergoing LBBAP and identify predictors of QRS width variation following implantation<strong>.</strong></span></span></span></span></span></p>

<p style="text-align:justify"><span style="font-size:medium"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="color:#000000"><strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Methods: </span></span></strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">We conducted a retrospective cohort study including consecutive patients who underwent LBBAP between October 2021 and October 2025 at a tertiary centre. Demographic, procedural, and electrocardiographic parameters were collected at implantation and first interrogation (at 1<sup>st</sup> month). QRS variation (&Delta;QRS = paced &minus; intrinsic) was used as a continuous marker of electrical response. Between-group comparisons were performed using parametric and non-parametric tests, including Kruskal&ndash;Wallis analysis for type of pacing capture. Linear regression was applied to identify predictors of &Delta;QRS. </span></span></span></span></span></p>

<p style="text-align:justify"><span style="font-size:medium"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="color:#000000"><strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Results: </span></span></strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">A total of 120 patients (mean age 74 &plusmn; 15 years; 29% female) were included. The pacing indication was bradyarrhythmia in 92.5% and cardiac resynchronization in 7.5%. The most frequent capture types were left fascicular pacing (45.8%) and left bundle branch pacing (38.3%), while stylet-driven leads were used in 38% of procedures and the axillary approach in 51%. Baseline QRS duration was 135 &plusmn; 35 ms, decreasing to 115 &plusmn; 16 ms post-implant (mean &Delta;QRS = &ndash;17.5 &plusmn; 39 ms). In univariable linear regression, baseline QRS &ge; 120 ms (B = &ndash;47.9 &plusmn; 7.6 ms, p &lt; 0.001) and type of pacing capture (B = 5.7 &plusmn; 1.9 ms, p = 0.003) were associated with QRS narrowing, whereas transcatheter aortic valve replacement (TAVR), LVEF &lt; 50%, and type of lead were not significant predictors. The Kruskal&ndash;Wallis test confirmed differences in QRS narrowing across the types of pacing capture (p = 0.033), with LBBP and left fascicular pacing showing greater electrical improvement compared with deep or left septal pacing.</span></span></span></span></span></p>

<p style="text-align:justify"><span style="font-size:medium"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="color:#000000"><strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">Conclusion: </span></span></strong><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif">In patients undergoing LBBAP, QRS narrowing was frequent and influenced by both baseline QRS duration and type of pacing capture. Conduction system pacing (LBBP and fascicular pacing) achieved greater electrical synchronization compared to septal pacing. These findings support the physiologic advantage of conduction system capture.</span></span></span></span></span></p>