[SCD-FORUM] 149E Mechanisms of T Wave Alternans Dr. Verrier

[SCD Symposium]

Comment on Mechanisms of T Wave Alternans 
Whereas T-wave alternans (TWA) is a unitary phenomenon, namely a repeating ABAB pattern in the amplitude and morphology of the T wave, it is likely that the underlying mechanisms differ as a function of pathophysiologic state.  This inference is supported by the fact that the clinical presentation of TWA varies markedly.  For example, in the classic presentation of the long QT syndrome, the entire T wave may alternate, even bidirectionally, above and below the isoelectric line.  In the Brugada syndrome, the terminal portion of the T wave alternates.  In the prevalent condition of ischemic heart disease, alternation is concentrated in the ST segment and first half of the T wave.  Experimental studies with fluorescent dyes suggest that derangements in intracellular calcium cycling underlie ischemia-induced TWA.  
Overall, these observations emphasize the need to consider the particular pathophysiologic state in the effort to uncover the pathophysiologic bases for TWA.  Increased understanding of this marker of cardiac electrical instability could help to tailor therapeutic interventions aimed at reducing the magnitude of TWA.  This is especially important that TWA is not only a marker of arrhythmic risk but also a potential arrhythmic trigger.  
Dr. Verrier 

Dr. Richard L. Verrier, F.A.C.C. 
Associate Professor of Medicine, Harvard Medical School 
Beth Israel Deaconess Medical Center 
Harvard-Thorndike Electrophysiology Institute 
Harvard Institutes of Medicine 
77 Avenue Louis Pasteur, Room 223 
Boston MA 02115 
Phone: 617-667-0730/FAX: 617-975-5270 
Email: rverrier at bidmc.harvard.edu