T wave alternans

Sudden cardiac death remains a preeminent public health problem. Despite advances in preventative treatment for patients known to be at risk, to date we have been able to identify, and thus treat, only a small minority of these patients. Therefore, there is a major need to develop noninvasive diagnostic technologies to identify patients at risk.

Although electrical alternans (alternating amplitude from beat to beat on the electrocardiogram) has remained an electrocardiographic curiosity for more than three quarters of a century, we have only recently recognized that it can be a harbinger of sudden cardiac death. Using methods for analyzing the statistical properties of beat-to-beat fluctuations in the morphologic features of the electrocardiogram, we and others have confirmed that alternans affecting the T wave (i.e., T-wave or repolarization alternans) may be closely associated with the genesis of ventricular arrhythmias.

Moreover, repolarization alternans in vivo that may be physiologically important can be subtle enough to preclude visual detection on the electrocardiogram yet readily measurable with appropriate techniques. We have developed a technique with the capacity to detect visually inapparent beat-to-beat oscillations of the surface electrocardiogram electrical alternans measured from the surface electrocardiogram may ultimately serve as a noninvasive marker of susceptibility to life-threatening ventricular arrhythmias. Studies have found that repolarization alternans is as effective as invasive electrophysiologic testing in predicting arrhythmic events.