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Figure 1 A typical episode of T-wave alternans (Case 1). (A) R(–) refers to the 10 cycles immediately preceding the alternans episode (from R–10 to R–1). R refers to the alternans cycles (R0, onset, and R14, the last measured alternans cycle). R(+) refers to the 10 cycles immediately succeeding alternans episode (R+1, the first, and R+10 the last cycle measured). (B) Graph showing the sequence of these cardiac cycles. Note that the alternans cycles (from R0 to R14) are expressively shorter than the preceding and succeeding cycles. At the bottom (asterisk), a nice demonstration is shown of concomitant great variability of QT intervals, while TWPA is depicted. The transition of the last cycle of alternans and the first cycle after alternans is not continuous.
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