Series expansion of the defibrillating current in a spherical shells model

The electric field set up during a defibrillation shock can be investigated in a spherical shells model (SSM). Current is injected from defibrillation pads at the body surface, and the transmembrane potential can be calculated in the heart. The simplified geometry makes possible an analytical solution, which speeds up the simulations and provides good insight into the underlying physics. When the coefficients of the series expansion for the applied current are expressed in terms of Legendre polynomials, the computational speed of the SSM is boosted even further, and pad placement chosen much more freely