A. Microvolt T-wave Alternans
Cambridge Heart, Inc. has provided an interesting instru¬ment that measures T-wave alternans. This test measures extremely subtle beat-to-beat fluctuations in a person’s heartbeat called T-wave alternans. These tiny heartbeat variations are measured at one millionth of a volt.
B. Clinical Study: NIH Study
This study was undertaken to determine the value of microvolt T-wave alternans testing.
Study question: T-wave alternans would be associated with increased risk of arrhythmic events in patients with left ventricular dysfunction; the association would be independent of the etiology of congestive heart failure (ischemic vs. nonischemic).
Method: The study enrolled 590 patients with congestive heart failure who had an ejection fraction of less than 40% and had no prior history of arrhythmia. Patients were excluded if they had arrhythmia, particularly atrial fibrillation or flutter, unstable coronary artery disease, and heart failure New York Heart Association class IV.
Results: T-wave alternans was a strong predictor of mortality in patients with left ventricular dysfunction independent of ejection fraction and etiology. In this study 34% of the patients tested negative and 66% positive or indeterminate. Patients with a negative T-wave alternans had an extremely low degree of mortality rate, 1%; patients with a negative T-wave alternans had an extremely low 2-year mortality rate (1%). Figure 13 shows sustained alternans with onset of less than 110 beats per minute. This is consistent with a positive tracing.

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