Reentrant arrhythmias and their control in models of mammalian cardiac tissue

We use detailed biophysical and simplified models of excitation propagation in heart muscle to study the properties of reentrant arrhythmias. Using a detailed model of excitation combined with a bidomain description of propagation and action of electric current, we have obtained a theoretical estimation for the defibrillation threshold consistent with experimental data. Reentry acts as a spiral wave, propagating around a region of block, the core. A series of properly timed low-voltage stimuli can cause directed "resonant" drift of this block and act as a low-voltage defibrillation strategy. Experimentally observed activation patterns in fibrillating tissue are more complicated than the simplest spiral wave patterns. This is due to complicated geometry, the 3-dimensional nature of the tissue, and its anisotropy and inhomogeneity. However, some fibrillation patterns can be produced by a single reentrant wave, modulated by inhomogeneous tissue properties and Wenckebach frequency division.