Rotors and Spiral Waves in Two Dimensions

Reentrant arrhythmias are the most common and potentially life-threatening of the cardiac arrhythmias and can be anatomically or functionally based. Anatomic reentry involves pathways that encircle a large anatomic obstacle (a region that is unexcitable under any conditions, occupies a fixed area, and has a border that is structurally defined) and is generally conceptualized in terms of a tissue ring. 1 Examples involve reentry in Purkinje bundles, bundle branches, the atrioventricular node, and muscle around the tricuspid valve. 2 On the other hand, functional reentry does not require a central anatomic obstacle and underlies many ventricular and atrial tachycardias and fibrillation. Mechanisms of functional reentry have been described in terms of leading circle, spiral wave, figure-of-eight, and anisotropic reentry. 3 All of these forms of reentry may be viewed as variants of rotating waves (rotors) that exhibit a repetitive, self-sustained, circulating spread of activation in which different behaviors emerge, depending on the particular combination of cellular excitatory/refractory properties and tissue structure.