A fully coupled modular finite element framework for investigating the impact of myocardial contraction on magnetocardiography magnetic field maps

Abstract More accurate mechanistic modeling of magnetocardiography is crucial for clinically guiding medical professionals in diagnosing heart diseases. The bioelectric current in the heart generates an electromagnetic field on the body surface. Although previous studies have highlighted the role of myocardial electromechanical feedback in electrophysiological output, its impact on magnetic fields remains underexplored. In this work, we first explore the effect of myocardial contraction on magnetic field maps (MFM) by proposing a fully coupled modular finite element framework. The solution of myocardial transmembrane potentials (TMPs) is primarily derived by considering the ion current activated by excitation in the static ventricle and the ion current induced by stretching during myocardial contraction. After defining the myocardial fiber orientation, the active stress, which varies with the TMPs, is decomposed additively along the fiber direction to simulate ventricular mechanical contraction. The TMPs are then used to calculate the impressed current density in the heart, and the volume conduction problem is solved via current conservation to determine the total current density in the torso. This total current density is subsequently used to solve the quasi-static magnetic problem. The accuracy of the calculation framework was assessed both qualitatively and quantitatively by comparing MFM under static ventricular and myocardial contraction conditions.