Review

The term “rotor ” is becoming a household name in cardiac electrophysiology. It applies to the organizing source of func-tional reentrant activity, particularly in the context of tachy-cardia and fibrillation. Emerging evidence clearly supports a major role for rotors as the drivers of cardiac fibrillation in animal models and in humans. Remarkably, much of what we have learned about the dynamics of rotors and the spiral waves generated by them derives from the field of compu-tational biology and from the study of wave propagation in excitable media. In the heart, the atria and ventricles share similar dynamics of electric wave propagation despite their vastly different geometry, global structure, and ionic mecha-nisms. More importantly, the behaviors of the electric rotors and spiral waves that form in their respective walls are also similar and may be analyzed using tools derived from the study of nonlinear systems. Thus, we make an attempt to rec-oncile such concepts with the more traditional ideas about mechanisms of cardiac fibrillation. First we set our current knowledge of reentry in a historical context, and then briefly define the basic notions and the terminology used through-out the article. Subsequently, we review our current under-standing of how rotors are initiated and the technologies that are used to localize them in the atria or ventricles, as well as to quantify their properties, including their dynamics and frequency of activation. We then present evidence demon-strating the similarities in the dynamics of rotors and thei