  Developing new methods for predicting electromagnetic instabilities in
cardiac activity is of primary importance. However, we still need a
comprehensive view of the heart's magnetic activity at the tissue scale. To
fill this gap, we present a model of soft active matter, including
thermo-electric coupling, suitably modified to reproduce cardiac magnetic
field. Our theoretical framework shows that periodic stimulations of cardiac
cells create an external magnetic field evidencing restitution features of
nonlinear cardiac dynamics and magnetic restitution curves better discriminate
instabilities and bifurcations in cardiac activity. This new framework lays the
foundation for innovative, non-invasive diagnostic tools for cardiac
arrhythmias.
