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T wave (repolarization) alternans: Clinical aspects

Sanjiv M Narayan, MD, PhD
Section Editor
Ary L Goldberger, MD
Deputy Editor
Brian C Downey, MD, FACC


T-wave alternans (TWA) refers to periodic beat-to-beat variability in the timing, shape, and/or amplitude of T-waves on the surface electrocardiogram (ECG) [1,2]. TWA therefore reflects sudden changes in temporal heterogeneity in ventricular repolarization, which is an important mechanism underlying reentrant arrhythmias [3,4].

Despite the term "T-wave" alternans, alternating behavior may also involve the ST segment and U wave (figure 1) [2,5-8]. As a result, the term ventricular repolarization alternans may be more accurate, but is rarely used.

TWA of sufficient magnitude to be seen with visual inspection is uncommon. With the development of computerized filtering and spectral analysis tools, TWA on the order of microvolts can be detected (figure 2), and microvolt TWA (MTWA, now often used synonymously with TWA) is both sensitive and specific for predicting ventricular arrhythmias in a number of clinical scenarios [1,2,7,9-16].

Clinical risk stratification for sudden cardiac death typically focuses on the presence of a reduced left ventricular ejection fraction and the presence of heart failure. However, these parameters identify only a minority of individuals who will die suddenly, and also identify others who will not suffer lethal ventricular arrhythmias [1,2]. As a result, there is continued interest in additional electrophysiologic indices for risk prediction, of which one of the most promising remains TWA [2].

The clinical utility of TWA will be reviewed here. The technical aspects and methods for analyzing TWA are discussed separately. (See "T wave (repolarization) alternans: Technical aspects".)

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Literature review current through: Nov 2017. | This topic last updated: Aug 09, 2017.
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