Effect of Contact Force on Local Electrical Impedance in Atrial Tissue - an In Silico Evaluation.

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 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 has not yet been characterized in depth. In this study, we applied several CF to a catheter in contact with a tissue patch modeled as healthy and scar atrial myocardium whose thickness was varied in anatomical ranges to study the impact of the mechanical deformation the LI measurements. When applying CF between 0 and 6g, in silico LI ranged from 160 $\Omega$ to 175 $\Omega$ in healthy my-ocardium, whereas 148 $\Omega$ and 151 $\Omega$ for scar tissue. Increasing CF in scar tissue up to 25 g, increased LI up to 156 $\Omega$ . The model was validated against clinically measured LI at different CF from AF patients. Simulation results applying identical CF in both tissues yielded lower LI values in scar. Moreover, LI increased in healthy and scar tissue when the thickness and CF were increased. 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 represents clinical LI measurements with and without mechanical deformation in a tissue model.