T-wave alternans quantification: which information from different methods?

T-wave alternans, qualitatively defined as every-other-beat alternations of the T-wave morphology, has no standardized quantitative definition yet. Differences in quantitative information provided by the fast-Fourier-transform spectral method (FFTSM), the modified-moving-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 T-waves maximum-amplitude difference (A_MAX) of 100 μV and mean-amplitude difference (A_MEAN) of 50 μV; and uniform the second (UNI_TWA), with A_MAX= A_MEAN=100 μV. Application of FFTSM, MMAM, and AMFM to TRI_TWA yielded 57 μV, 100 μV, and 50 μV TWA amplitude estimation, respectively. Instead, 100 μV TWA amplitude was provided by each method after their application to UNI_TWA. Thus, FFTSM and AMFM provide estimates of A_MEAN, while MMAM of A_MAX.