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Figure 1 T-wave alternans (TWA) of increasing subtlety detected through the years. (A) Gross alternans of elevated ST/T-segments in a patient with angina pectoris preceding ventricular tachycardia (VT); (B) Visible alternans of T-wave polarity in a woman without angina, heralding polymorphic VT; (C)Subtle but visible TWA after tachycardia termination, without arterial pressure alternans (bottom); (D)Visually inapparent microvolt-level TWA, uncovered by digital signal processing (8,23). *The more positive T-wave of each alternating pair. Panel A was reprinted with permission from reference 11. Panel B was reprinted with permission from reference 22, Copyright ^©2006 Massachusetts Medical Society. Panel C was reprinted with permission from reference 21.