Feasibility and safety of left bundle branch-optimized cardiac resynchronization therapy (LOT-CRT): a single-center experience

Background: Left bundle branch-optimized cardiac resynchronization therapy (LOT-CRT), combining left bundle branch area pacing (LBBAP) with coronary sinus (CS) pacing, is a novel strategy for patients with heart failure and electrical dyssynchrony. It may offer superior electrical and clinical outcomes compared to conventional CRT or LBBAP alone. Despite promising early results, data remain limited.

Objective: We report our single-center experience as part of a non-randomized prospective registry study, focusing on the feasibility, safety, and short-term efficacy of LOT-CRT implantation.

Methods: A total of 40 non-consecutive patients, who were evaluated for de-novo CRT-implantation in the Heart and Vascular Center or Bad Segeberg in Germany over a 2-year period between March 2023 and April 2025, underwent LOT-CRT-implantation. 3 (7.5%) of our patients received an implanted cardioverter defibrillator (ICD).

A stylet-driven pacemaker lead (Biotronik Solia S60) was used for LBBAP implantation via a 3-dimensional delivery sheath (Biotronik Selectra 3D). Coronary sinus (CS) lead implantation was performed in a standard manner as for conventional biventricular CRT procedures.

All procedures were performed under deep sedation and under continuous 12-lead ECG monitoring and underwent post-operative device optimization to ensure the best ECG results. We report on the first LOT procedures performed in our center and by our operators.

Results: Our cohort consisted of 22 (55%) male and 18 (45%) female patients with a median age of 80 (Q1=74; Q3=83) years and a median left ventricular ejection fraction (LVEF) of 30% (Q1=25; Q3=40). 20 (50%) patients had a dilated cardiomyopathy (CMP), 18 (45%) had ischemic CMP, and one patient had a hypertrophic non-obstructive CMP, who underwent atrioventricular (AVN) ablation. One patient had symptomatic heart failure with a preserved LVEF and received LOT-CRT before atrioventricular (AVN) ablation. 9 (22,5%) of all of our patients underwent AVN ablation after the implantation (Table 1).

All LOT-CRT implantation procedures were successful. One major periprocedural complication (2.5%) occurred—an atrial lead dislocation, which was successfully revised three days postoperatively. Additionally, one minor complication was observed: a symptomatic arm vein thrombosis on the implantation side, which was treated with oral anticoagulation.

The mean procedure time was 83 (Q1=69; Q3=97) minutes, fluoroscopy time was 14.5 (Q1=12; Q3=23) minutes, and the mean dose area product was 934 (Q1=580; Q3=1907) cGy·cm²) all comparable to values reported for conventional biventricular CRT implantation. Following LOT-CRT implantation, a significant QRS duration reduction of 27% was observed—from a mean baseline of 155 ms to 113 ms—excluding patients without pre-existing bundle branch block in whom CRT was indicated due to high-grade AV block or planned AV node ablation.

Conclusion:  LOT-CRT implantation in our initial experience proved to be feasible and safe, showing significant QRS narrowing and promising clinical outcomes.

Table 1: