Mechanisms underlying the propagation of activation in cardiac tissue

Local circuit current flow governs the propagation of activation in cardiac tissue. The anisotropie conductivity of cardiac muscle can explain the more efficient charging of the membrane capacitance and the higher safety factor of propagation in the direction transverse to the long axis of cardiac cells, without invoking spatial nonuniformities of membrane properties. While the underlying mechanisms of major arrhythmias may involve perturbations in both intercellular coupling and membrane properties, reentrant tachyarrhythmias can probably be explained solely in terms of the anisotropie conductivity of cardiac muscle.