Clinical applications of T-wave alternans assessed during exercise stress testing and ambulatory ECG monitoring

Analytical methods to measure T-wave alternans (TWA), a beat-to-beat fluctuation in the morphology of the ST-segment and T wave in the electrocardiogram (ECG), have been developed to address the unmet challenge of identifying individuals at increased risk for sudden cardiac death. Conventional noninvasive markers including left ventricular ejection fraction have significant limitations as many individuals who die suddenly have relatively preserved ventricular mechanical function. TWA is an attractive marker as it is closely linked to ECG heterogeneity and abnormalities in calcium handling, key factors in arrhythmogenesis. The objectives of this review are to summarize the clinical evidence supporting use of TWA in risk stratification and to discuss its current and potential applications in guiding device and medical therapy.