Complex dynamics in a three-dimensional realistic anatomical structure of the human atria, with scroll waves initiated on the left atrium free wall. The views show the left atrium on the left and the right atrium on the right. A–C. The CM meanders throughout both atria and quickly establishes multiple reentrant waves. Transient breakup and recombination occurs in the right atrium near the crista terminalis and caval veins. Transient pinning to the right pulmonary veins also occurs, as shown in C, but because the period of the reentrant wave is longer than the time it takes to circulate around the vein ostia, the wave cannot remain pinned. Times are (A) 10.47 s, (B) 10.64 s, and (C) 12.48 s. D–F. The scroll wave initiated using the NMf-X terminates at the left pulmonary veins, where it becomes largely pinned. Transient unpinning occurs because the period of the reentrant wave is slightly longer than the time to travel around the ostia, but the wave soon re-pins to the veins and the process repeats. Times are (D) 3.09 s, (E) 3.12 s, and (F) 3.15 s. Grayscale indicates membrane potential in mV as in Fig. 8.