Effect of Contact Force on Local Electrical Impedance in Atrial Tissue - an in silico Evaluation

Carmen Martinez Anton1, Jorge Sánchez2, Andreas Heinkele3, Laura Anna Unger4, Annika Haas5, Kerstin Schmidt5, Armin Luik5, Axel Loewe6, Olaf Doessel3
1KIT, 2Institue of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), 3Institute of Biomedical Engineering, Karlsruhe Institute of Technology, 4Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), 5Medizinische Klinik IV, Städtisches Klinikum Karlsruhe, Academic Teaching Hospital of the University of Freiburg, 6Karlsruhe Institute of Technology (KIT)


Abstract

Regions with pathologically altered substrate have been identified as potential drivers for atrial fibrillation (AF) maintenance. Recently, local impedance (LI) measurements have gained attention as a voltage surrogate for atrial substrate assessment as it does not rely on electrical activity of the heart. However, an appropriate electrode-tissue contact force (CF) is needed and its effect on the LI measurements in the substrate has not yet been characterized in depth. In this study, several CF are applied to a catheter in direct contact with a tissue patch, model as healthy and scar atrial myocardium whose thickness was varied in anatomical ranges, to study the impact of the mechanical deformation on the LI measurements. The model was validated against clinically measured LI at different CF from AF patients. Simulation results applying identical CF in healthy and scar tissue yielded lower LI values in scar. Moreover, LI increased in both cases when tissue thickness and CF were increased. When applying CF between 0 and 6 g, in silico LI ranged from 160 Ω to 175 Ω in healthy myocardium, whereas 148 Ω and 151 Ω for scar tissue. Increasing CF in scar tissue up to 25 g, increased LI up to 156 Ω. Given the results of our study, we conclude that in silico experiments can not only distinguish between healthy and scar tissue by combining CF and LI, but also that our simulation environment faithfully represents clinical LI measurements with and without mechanical deformation in the tissue model.