This paper compares several cellular-level models of cardiac activation according to the
sources that are generated and their macroscopic fields. Since macroscopic field patterns
and strengths are well documented, by comparing the models of cardiac activation, the more
controversial microscopic processes can be evaluated. The results show that it is most likely
that both macroscopic and microscopic activation of cardiac tissue are uniform processes,
and in a direction that is transverse to the fiber axis.