[T-wave alternation: a new method for identifying patients at risk of malignant ventricular tachyarrhythmia].

T wave alternans (TWA) is a change, in the microvolt range, of T wave amplitude on ABABAB sequence. TWA depends on heart rate, being optimally analyzed at a target frequency of 110 b/min. Initial studies used atrial pacing to reach the target frequency and reported a sensitivity and specificity of 89% for TWA in predicting tachyarrhythmic events. Subsequently, similar results were obtained using ergometric test to reach the target frequency, a less invasive and more "physiologic" approach to increase heart rate. This method became therefore the elective system to increase heart rate in order to evaluate the presence of TWA by means of spectral analysis. At present, various groups of high arrhythmic risk patients have been evaluated, including those with a recent myocardial infarction, congestive heart failure, implantable cardiac defibrillator and clinical indication to programmed ventricular stimulation. In all clinical conditions analyzed, TWA analysis demonstrated a good diagnostic accuracy, suggesting a possible clinical use of the test in these settings.