Magnetically induced myocardial electric fields: a finite element study

A moderately detailed three-dimensional finite element model (FEM) of the canine thorax is used to determine magnetically induced myocardial electric fields produced by x, y, z gradient coils and a pancake shaped coil. The coil positions and excitations used in our simulations correspond to experimental studies in which cardiac stimulation was observed. Threshold myocardial electric fields for magnetic stimulation are estimated from our results by assuming that the maximum myocardial electric field excites the heart. Computed electric field magnitudes for the respective coil configurations corresponding to these studies at similar pulse durations yield threshold values that are not all self-consistent, suggesting that the maximum induced electric field in the myocardium may not by itself be responsible for magnetically induced myocardial stimulation. These results highlight the importance of elucidating the appropriate activation function for magnetic stimulation of the heart