In-vivo durability assessment of a stylet-driven CSP ICD lead for conduction system pacing using a human beating heart model
H Liu, R Shaw, W Alleman, B James, C Nycum, K VictorineAbstract
Background
Conduction system pacing (CSP) has emerged as a promising approach to cardiac physiologic pacing with a pacemaker lead. However, durability has not been fully studied for stylet-driven CSP ICD leads implanted in the left bundle branch area (LBBA). Some ICD leads are currently enrolled in clinical studies to evaluate their effectiveness for LBBA implant.
Purpose
The purpose of this study was to evaluate the long-term durability of a stylet-driven CSP ICD lead, using simulations and bench tests to confirm its safety for left bundle branch area (LBBA) implantation.
Methods
A high-resolution human beating heart model was utilized for simulating deformation of a lead in a cardiac cycle. The cyclic bending of a CSP ICD lead was analyzed in both diastolic and systolic states. The distal end of the CSP ICD lead was embedded into the interventricular septal tissue with a nominal length of 10 mm. Three variation groups have been established for evaluating the long-term durability of the lead: 1) implant variations including implant location, implant angle (guided by the recent publication), lead slack in the right atrium and implant depth in the septum ; 2) heart physiology: fiber orientation, tissue stiffness, contractile level of heart muscle, and electrical pattern (e.g. left bundle branch block); 3) heart size scaling from average size Asian population to average size Western population with a potential cardiomyopathy (Figure 1). Safety factor (SF) was determined using the bending curvature and mechanical properties of the conductor (Figure 2). A higher safety factor indicates less bending stress on the lead and higher conductor durability. A bench-top fatigue test was implemented at higher stress levels, thus at lower safety factors, than the modeling analysis cohort.
Results
A total of 29 scenarios have been included in the modeling cohort. The maximal bending curvature was observed between the ring electrode and the shock coil. The average safety factor across all 29 cases was determined to be 1.87 with a standard deviation of 0.30. The case with the lowest safety factor of 1.53 within the cohort corresponded to a relatively small heart (RV diameter of 31.6 mm). The durability of the lead conductor was verified through successful lead fatigue testing at a conservative safety factor compared with the simulation cohort.
Conclusions
A human heart modeling cohort has demonstrated chronic reliability of the conductor based on the bending curvature and material strength (SF>1). Successful bench testing at extreme conditions beyond expected in-vivo conditions from human heart modeling verifies the long-term durability of the ICD lead implanted in the LBBA.Variations of in-silico modleing casesPipeline of calculating safety factors