Optimizing Radiofrequency-Assisted Lead Penetration into Swine Interventricular Septum Using Pacing Leads: A Systematic In Vitro Assessment.

Background: Left bundle branch area pacing (LBBAP) is a promising physiological pacing modality, but fibrotic or calcified interventricular septal tissue can prevent lead advancement. Radiofrequency (RF) energy has been applied in transseptal puncture and lead extraction, but its optimal use for pacing lead penetration has not been systematically evaluated.

Objective: To assess the safety and efficacy of different RF energy settings for facilitating pacing lead penetration through the interventricular septum in an ex vivo swine model.

Methods: Freshly excised swine hearts (n=6) were immersed in a temperature-controlled (37°C) circulating saline bath. The SelectSecure 3830 lead was positioned manually against the septum under fluoroscopic guidance. RF energy was delivered using an ERBE VIO300S electrosurgical generator in cutting mode across 12 combinations: four energy levels (10, 20, 30, 55 W) and three durations (1, 2, 3 s). Additionally, spark mode(20,30W) was tested with 3 times and 5 times of sparking. Each combination was tested six times. Outcome metrics included penetration success (rupture of the RV septal endocardium), safety markers (significant bubble formation, tissue charring), and histological assessment of myocardial injury.

Results: At 10 W, penetration was not achieved in any trial. At 20 W, application for 1-2 seconds achieved an 88.9% success rate with minimal collateral injury. In contrast, power ≥30 W or durations >2 seconds significantly increased bubble formation (up to 94%) and deep myocardial necrosis. Histology confirmed that 20 W/1-2 seconds produced sharp cleavage of fibrotic tissue with preservation of deeper myocardial architecture. Spark mode was less stable and reproducible compared with optimized continuous settings.

Conclusions: RF-assisted pacing lead delivery using 20 W for 1∼2s represents an effective and safe strategy for overcoming superficial septal fibrosis in ex vivo settings. This technique may offer a viable rescue option during challenging LBBAP procedures.