gms | German Medical Science

Question: The bidomain model is the most realistic mathematical expression for macroscopic simulation of cardiac muscle. However, it is computationally much more demanding than the less realistic monodomain model. A bidomain model of the human heart depends on expensive supercomputers to run, while a monodomain model can work on a standard PC. We have investigated if a monodomain model suffices for propagation studies.

Method Used: We developed a bidomain reaction-diffusion model of the electrical activity of the human heart, incorporating a realistic cardiac anatomy, anisotropic ventricles with transmural fiber rotation, ventricular blood, and a recent ionic model for the human ventricular myocyte. A 0.2-mm grid was used to discretize the equations, leading to 50 million nodes. The model can also operate in monodomain mode, and as a separate forward model to compute extracellular potentials (Ve) from given membrane potentials (Vm). This allows a fair comparison of monodomain and bidomain results.

Results: The differences between the monodomain and bidomain models in propagating Vm and Ve were very small. Propagation was 5% faster in a bidomain model. Simulated Vm were not significantly different. Differences in Ve were very small compared to differences due to the inclusion of intracavitary blood.

Conclusion: Monodomain models can be used to compute propagating action potentials in simulations that do not involve applied currents. A separate forward model can be used to compute highly realistic Ve from the simulated Vm. Although the Ve distribution implicit to the monodomain formulation differs much from that produced by a bidomain model, the difference is a smooth function that contributes little to the dynamics of Vm. Consequently, the monodomain model produces an appropriate distribution of membrane currents to calculate Ve afterward.