T-Wave Alternans Quantification: Which Information from Different Methods?

T-wave alternans, qualitatively defined as every-otherbeat alternations of the T-wave morphology, has no standardized quantitative definition yet. Differences in quantitative information provided by the fast-Fouriertransform spectral method (FFTSM), the modifiedmoving- average method (MMAM), and our heart-rate adaptive match filter method (AMFM) were analyzed here making use of two synthetic ECG tracings with stationary TWA: triangular the first (TRI_TWA), with Twaves maximum-amplitude difference (AMAX) of 100 mu V and mean-amplitude difference (AMEAN) of 50 mu V; and uniform the second (UNI_TWA), with A(MAX)= A(MEAN)= 100 mu V. Application of FFTSM, MMAM, and AMFM to TRI_TWA yielded 57 mu V, 100 mu V, and 50 mu V TWA amplitude estimation, respectively. Instead, 100 mu V TWA amplitude was provided by each method after their application to UNI_TWA. Thus, FFTSM and AMFM provide estimates of AMEAN, while MMAM of AMAX.