Observations of interventricular septal behavior during left bundle branch pacing

IntroductionLeft bundle branch pacing (LBBP) involves the deployment of the lead deep inside the septum. Penetration of the septum by the lead depends on the texture of the septum, rapidity of rotations, operator experience, and implantation tools.ObjectivesThe aim of our study was to assess the behavior of the lumenless lead during rapid rotations and the physiological property of the interventricular septum(IVS) during LBBP.MethodsPatients undergoing LBBP between January 2021 and December 2022 were retrospectively included in the study.ResultsAmong 255 attempted patients, 20 (7.9%) had procedural failure(no LBB capture-four, inability to penetrate septum-seven, and dislodgements after sheath removal-nine). Septal penetration achieved in 248/255 patients (97.2%). Lead movement inside the IVS was assessed by lead traverse time. Based on the behavior of the IVS (n = 255), three different responses were noted. Type-I response(normal/firm septum) in 93.7% (n = 239) characterized by constant and progressive movement of lead. Neither perforation nor further change in premature-ventricular-complex morphology beyond M-beat were observed despite additional few unintentional rotations indicating the protective mechanism of LV-endocardium. Type-II response(soft/cheesy septum) in 3.5% (n = 9) characterized by hyper-movement of lead without resistance due to altered texture of septum and poor LV subendocardial barrier resulting in perforation. No patients in this group had LV dysfunction or associated coronary artery disease. In type-III response, seen in 2.8% (n = 7), lead could not be penetrated due to scar in IVS.ConclusionThree different patterns of responses were observed during LBBP. The most distinct type-ll response was associated with soft/cheesy septum with hyper-movement of the lead predisposing for future dislodgments in patients without structural heart disease. Septal penetration in left bundle branch pacing depends on its texture, rapidity of rotations, operator experience, and implantation-tools. Based on the septal behavior, three responses were noted. Type-I (normal/firm septum; 93.7%) characterized by constant and progressive lead movement, Type-II (soft/cheesy septum; 3.5%) hyper-movement resulting in perforation, and in Type-III (2.8%), lead could not be penetrated due to septal scar.image