Basic Science for the Clinical Electrophysiologist Emergence of Complex Behavior An Interactive Model of Cardiac Excitation Provides a Powerful Tool for Understanding Electric Propagation

We have developed a straightforward, physiologicallybased mathematical in silico model of cardiac electric activity to facilitate understanding of the fundamental prin-ciples that determine how excitation propagates through the heart. Despite its simplicity, the model provides a very powerful teaching tool. In fact, its simplicity is integral to the model’s utility. The contrast between the minimal set of rules that govern the model’s function and the widely varied complex behaviors it can manifest offers insight into the nature of emergent behavior in wave propagation. Emergence in this context refers to the richness of the tissue activation patterns that arise from the aggregate behavior of the simple cells that comprise the tissue. Each cell can be active, inactive, or refractory and interacts only with its immediate neighbors. From these simple building blocks, very elaborate global behaviors emerge