September 13, 2012 - 1:00pm EDT
Presented by:
Richard L. Verrier, Ph.D.,
Associate Professor of Medicine,
Harvard Medical School, Division of Cardiovascular Medicine,
Beth Israel Deaconess Medical Center, Boston MA
Title: "Microvolt T-Wave Alternans: Guideline Statement for Clinical Practice"
View: (Archived Webinar Recording)
Abstract:
The presentation will review our recent consensus guideline that was published in the Journal of the American College of Cardiology (2011;58:1309–24). The electrocardiographic bases of microvolt T-wave alternans (TWA) (i.e., a beat-to-beat alternation in the morphology and amplitude of the ST- segment or T-wave) will be briefly reviewed. The main focus will be on TWA’s physiological basis and measurement technologies and its clinical utility in stratifying risk for life-threatening ventricular arrhythmias.
Signal processing techniques including the frequency-domain Spectral Method and the time-domain Modified Moving Average method have demonstrated the utility of TWA in arrhythmia risk stratification in prospective studies in >12,000 patients. The majority of exercise-based studies using both methods have reported high relative risks for cardiovascular mortality and for sudden cardiac death in patients with preserved as well as depressed left ventricular ejection fraction. Studies with ambulatory electrocardiogram-based TWA analysis with Modified Moving Average method have yielded significant predictive capacity. However, negative studies with the Spectral Method have also appeared, including 2 interventional studies in patients with implantable defibrillators. Meta-analyses have been performed to gain insights into this issue. Frontiers of TWA research include use in arrhythmia risk stratification of individuals with preserved ejection fraction, improvements in predictivity with quantitative analysis, and utility in guiding medical as well as device-based therapy.
Overall, it was concluded that it is reasonable to consider TWA evaluation whenever there is suspicion of vulnerability to lethal cardiac arrhythmias.
Speaker Bio:
Dr. Verrier’s research program focuses on sudden cardiac death, which claims >325,000 lives annually in the United States alone. His studies emphasize elucidation of pathophysiologic mechanisms and development of novel approaches for identifying individuals at risk for this mode of demise, which occurs without prodromes in at least 30% of cases. He has a longstanding interest in electrophysiologic markers of arrhythmia risk and in use of T-wave alternans as a therapeutic target.
He and his colleagues discovered and published in Science in 1991 evidence that a fundamental electrophysiologic phenomenon, “T-wave alternans,” a beat-to-beat fluctuation in the magnitude of this waveform, is capable of stratifying risk for life-threatening arrhythmia. Extensive series of experiments revealed that T-wave alternans is able to track effects of neural factors, myocardial ischemia, and other proarrhythmic influences. Conversely, physiologic and pharmacologic interventions that reduce the magnitude of alternans were found to be antiarrhythmic. These findings provided essential scientific underpinnings for utilizing alternans as a clinical marker of arrhythmic risk. Methodologies for quantifying alternans compatible with routine ambulatory ECG monitoring and exercise stress testing were developed, patented, and implemented and employed to demonstrate that this phenomenon is capable of assessing risk for arrhythmic events in post-myocardial infarction patients and in over 4,000 consecutive patients referred for routine exercise testing. This FDA-approved diagnostic risk assessment technology is now in use in clinics and hospitals worldwide. In May 2012, the Ministry of Health, Education, and Welfare approved its reimbursement in Japan.