Microvolt T-Wave Alternans and the MASTER Trial

Topic(s):  Arrhythmias
Date Posted: 1/27/2009

Expert: Melanie T. Gura, RN, MSN, CNS 1. What is T-wave alternans? T-wave alternans refers to a beat-to-beat alteration in the amplitude of the T-wave portion of the electrocardiogram tracing. These changes are small and are imperceptible to the naked eye. 2. What is microvolt T-wave alternans (MTWA) testing? MTWA is a noninvasive technique used measure T-wave alternans, and is a risk stratification tool to predict the likelihood of fatal arrhythmias and sudden cardiac death in patients with a history of myocardial infarction or cardiomyopathy. 3. What is the clinical utility of TWA testing? Prior trials have suggested that a negative T-wave alternans test indicates there is minimal risk of the patient developing ventricular tachyarrhythmias (VTA) and can therefore influence the treatment plan by sparing the risk and expense of surgery for implantation of an implantable cardioverter-defibrillator (ICD). Conversely, a positive test result will allow more aggressive treatment of patients at high risk for sudden cardiac death. 4. What was the purpose of the MASTER Trial? The purpose of the MASTER trial was to evaluate use of MTWA testing for risk stratification for life-threatening ventricular tachyarrhythmic events among post-myocardial infarction (MI) patients with impaired ejection fraction undergoing ICD implantation. The hypothesis was that MTWA would predict ventricular tachyarrhythmias among patients with impaired ventricular function after MI. 5. What were the findings of the MASTER trial? The MTWA test was non-negative in 63% of patients and negative in 37%. There was no significant difference in the annual rate of VTAs between patients with non-negative and negative tests (6.3% and 5.0%, respectively). MTWA was not a predictor of VTEs. Total mortality was twice as high in non-negative patients than in the patients with a negative MTWA test. 6. What was the conclusion of the MASTER Trial? MTWA does not accurately identify post-infarction patients with ischemic cardiomyopathy who are at low risk of life-threatening arrhythmias. 7. What is the clinical significance of the trial? The patients in this study met the MADIT-II criteria for ICD implantation (CAD, EF <>