Pacing-induced multiple wave reentry

Atrial flutter can be caused through the formation of double-wave reentry. Our previous one-dimensional ring model of cardiac tissue had provided the insight into the mechanisms of multiple wave reentry. The object of the study is to demonstrate how to maintain numerous wavelets circulating around an excitable core simultaneously in a two-dimensional anisotropic atrial sheet. The sheet is composed of 100×100 atrial cells, and each cell is coupled by gap junctions. External current stimuli, S1-S5, are applied on the site of the membrane to induce multiple wave reentry. Results indicated that (1) a second sustained spiral wave can be generated by repeated spawning of wave fragment caused by wave-wave collisions; (2) transient three spiral waves can coexist by repeated cycles of wave-wave collisions; and (3) continuous spawning wavelets can be promoted during head-to-side wave collisions in the tissue with shorter refractoriness. In conclusion, the model simulations indicated that certain types of wave-wave collisions can cause electrical fragmentation patterns and suggested that multiple reentrant waves experience collisions with each other, which could lead to chaotic waves, considered as the possible pathway to fibrillation.