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Figure 2 "Orderly transition" from stable rhythm, via T-wave alternans (TWA), to ventricular fibrillation (VF). Electrocardiograms (ECGs) of canine hearts after the onset of ischemia (times in min:s) show period doubling to TWA, i.e., two clusters in the Poincarré plot (T-wave amplitude of each beat against its successor). Further multupling causes higher-order oscillations, complex forms, and then VF. Reprinted with permission from reference 28.