The Role of Myocardial Anisotropy in Arrhythmogenesis Associated with Myocardial Ischemia and Infarction

Myocardial Anisotropy in Ischemia and Infarction . Anisotropy is defined as any property of a system that differs depending on the direction in which it is measured. In the heart, the structure of the cardiac myocytes and their electrical coupling via gap junctions confer an anisotropy in the intracellular resistance to current flow in myocardial tissue. This in turn is responsible for anisotropy in conduction in which the velocity and uniformity of impulse conduction is dependent on its direction relative to the normal myocardial fiber orientation and any underlying pathological nonuniformities in cell orientation and coupling. How cells are coupled also influences refractoriness and excitability. Recent experimental evidence has implicated uniform and nonuniform myocardial anisotropy as important substrates that play a role in the initiation and maintenance of arrhythmias in the setting of ischemia and infarction. These studies may provide a focus for the development of new antiarrhythmic modalities that depend on the modulation of cell electrical coupling.