Is T-wave alternans T-wave amplitude dependent?

The possible dependence of T-wave alternans (TWA) on T-wave amplitude was investigated in 3 orthogonal leads (X, Y, Z) 20-min resting ECG recordings and in the derived vector magnitude (VM) from 176 healthy (H) subjects and 200 coronary-artery-disease (CAD) patients. After application of our adaptive-match-filter based method for parameterization of TWA in terms of its amplitude (TWA_A) and product-magnitude (TWA_PM, defined as the product of TWA_A times TWA duration), and once a TW_A parameter was defined for T-wave amplitude quantification, the existence of intra- and inter-subjects relationships of TWA_A and TWA_PM vs. TWA was tested. Compared to the H-population, the CAD-population showed a significant (P<0.05) increase of TWA_A (62 +/- 38 mu V vs. 54 +/- 25 mu V) and TWA_PM (4029 +/- 2974 beat mu V vs. 3107 +/- 1976 beat mu V) and a significant decrease of TW_A (298 +/- 194 mu V vs. 467 +/- 246 mu V). These repolarization changes, however, occurred with no significant intra- or inter-subjects relationships of TWA_A and TWA_PM vs. TW_A. Thus, in our CAD and H populations there was no evidence of TWA dependence on T-wave amplitude. (C) 2011 Elsevier Ltd. All rights reserved.