Visible T-wave alternans (TWA) has been reported since 1909, being, thus, not a recent finding. However, non-visible and far less rare microvolt TWA has gained importance because of its association with electrical disorders and the high risk for sudden cardiac death (SCD) or arrhythmic events,^– being assessed in several clinical trials and population studies, such as TWA in HF, ALPHA Study, REFINE Study, FINCAVAS, the collaborative study by Ikeda et al. and the MADIT-II-type research by Bloomfield et al. All those studies have in common the fact that they evidence the high negative predictive value of TWA regarding SCD or arrhythmic events, with low to intermediate positive predictive value.

A specialized software is used to analyze the microvolt TWA, the beat-to-beat variability that occurs in ventricular repolarization (ST segment and T wave) and that cannot be seen by the naked eye.^– The TWA allows indirect access to the increase in the dispersion to the action potentials of cardiac cells, a primordial factor in a sequence of events that will lead to reentry mechanisms and ventricular fibrillation, which will culminate with SCD. A fundamental property of its analysis is the high negative predictive power for the SCD risk that a normal TWA test has.

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