Electrical behavior of T-Wave polarity alternans in patients with congenital long QT syndrome
Fernando E. S. Cruz Filho, MD, FACCa,
Ivan G. Maia, MD, FACCa,
M.árcio L. A. Fagundes, MDa,
Rosa Celia P. Barbosa, MDa,
Paulo A. G. Alves, MDa,
Roberto M. S. Sá, MDa,
Silvia H. Boghossian, MDa and
Jose Carlos Ribeiro, MDa
a Hospital Pró-Cardíaco, Rio de Janeiro, Brazil
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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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Figure 2 Mean CL and QT intervals before, during, and after alternans. It becomes obvious from the graph that the CL remains fairly constant during the 3 min preceding the alternans and that a very sharp transient shortening of CL is associated with T-wave alternans.
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Figure 3 Graphic depiction of the mean values of R-R cycles and QT intervals from R–10 to R–1, from R0 to R14, and from R+1 to R+10. The discontinued line between R14 and R+1 refers to the transition of the last cycle of alternans and the first cycle after alternans. These cycles are not always necessarily continuous.
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Figure 4 Graph of hourly distribution of TWPA in a 24-h period. Note that the incidence of such episodes is higher during the daytime period (from 8 AM to 8 PM), with an impressive distribution during the morning (8 AM to noon).
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