Left bundle area pacing in hypertrophied hearts: An ex vivo ovine model to study deployment of pacing leads in thick septum

Background: Knowledge of lead biomechanics in a hypertrophied interventricular septum (IVS) may improve the success rate of left bundle branch area pacing (LBBAP) in these patients. Objectives: We sought to investigate the biomechanics of lead penetration in an ex vivo ovine model of a hypertrophied IVS and compare the behavior of lumenless leads (LLL) vs stylet-driven leads (SDL) in terms of torque transfer and penetrating capacity. Methods: Twenty fresh ex vivo ovine interventricular septae were excised to create a virtual hypertrophied IVS model by having 2 septae sandwiched together and placed in a custom-made clamp. Five different leads were driven into the hypertrophied IVS model with sheath support via a custom-engineered tool which allowed control of input rotation, forward movement, and measurement of torque transfer curves. Results: A total of 100 lead runs were completed which revealed the following 5 distinct patterns of lead behavior: (1) endocardial entanglement, (2) endocardial barrier, (3) drill, (4) myocardial barrier (only observed using LLL, P<.001), and (5) screwdriver (only observed using SDL, P<.001). The maximum torque during successful and deep penetration trended lower compared with when the lead failed to penetrate 2.78 ± 1.21 mN vs 3.6 mN ± 1.62 mN (P = .085). SDL was able to achieve a greater depth of penetration compared with the LLL (20.89 ± 6.46 mm vs 14.8 ± 2.39 mm; P<.001). Conclusion: Lead deployment patterns in hypertrophied septae vary between leads. SDL achieves deeper septal penetration at lower torque and faster forward motion than LLL.