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Figure 1 A representative case of a trend graph of alternans (left side) and the T-wave spectrum (right side) during exercise testing. An alternans voltage 1.9 µV with an alternans ratio 3 is found at a 0.5-cycle/beat frequency with a heart rate (HR) of >105 beats/min. VT = ventricular tachycardia; y.o. = year old.