Figure 4.7.

Conduction speed along different models of a linear strand of myocytes without ephaptic coupling (R_c = 0) as a function of the gap-junctional coupling strength g_GJ. The multiscale model reproduces the dynamics of the underlying microscale model across the entire range of values of g_GJ surveyed. In particular, notice that the multiscale model captures the level of gap-junctional coupling that yields propagation failure in the microscale model. By contrast, the macroscale model predicts substantially different values of g_GJ that lead to propagation failure for different numerical grid spacings. In particular, coarse macroscale grid spacings yield a model that predicts propagation failure at substantially higher levels of gap-junctional coupling than the micro- and multiscale models, and fine macroscopic grid spacings yield propagation success for substantially smaller values of g_GJ. It is interesting to note that if the macroscopic grid spacing is equal to the cell size (100 μm), then the macroscopic model is in perfect agreement with the micro- and multiscale models. Figure from Hand and Griffith [29].