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. Author manuscript; available in PMC: 2018 Nov 1.
Published in final edited form as: J Electrocardiol. 2017 Aug 10;50(6):717–724. doi: 10.1016/j.jelectrocard.2017.08.002

Figure 1. Calculating Alternans and Non-Alternans Time-Domain T Wave Variability.

Figure 1

This simplified diagram illustrates the differences between computing alternans (A) and non-alternans (B) variability of the T wave. In alternans variability (A), odd and even beats are streamed into two separate bins (green and black bins). An averaged beat is created for each bin, and the averaged bins were then superimposed. The root-mean-square (RMS) of the differences between these two averaged beats is computed over the entire T wave period. The average RMS over this window is reported as the time-domain TWA. In non-alternans variability (B), consecutive pairs are averaged first, then the RMS of the differences between averaged pairs is computed. We selected and reported the TWA and NARV from the ECG lead with largest liability values with least noise level.