T wave alternans

Those who are found to be at high risk would therefore benefit from the placement of a defibrillator device which can stop an arrhythmia and save the patient's life.

The amount of variation is small, on the order of microvolts, so sensitive digital signal processing techniques are required to detect TWA.

First recognized nearly a century ago, visually discernible alternans were linked to the rapid onset of ventricular tachyarrhythmias.

[citation needed] Research conducted in the early 1980s by Dr. Richard Cohen and his colleagues at MIT explored the idea that visually indiscernible alternans may be equally significant.

In addition, Dr. Joseph Smith, working with Dr. Cohen developed a methodology known as the Spectral Method which allowed measurement of alternans at the level of one microvolt.

[4] Patients who test MTWA positive or indeterminate for heart rate or dense ectopy (abnormal) should be referred to an electrophysiologist for further evaluation.

The Spectral Method requires a specialized exercise protocol and proprietary electrodes and washout of beta-adrenergic blocking agents to allow the patient to achieve a target heart rate of 105-110 beats/min.

The MMA method uses routine, symptom-limited exercise stress testing or ambulatory ECG monitoring and standard electrodes and requires that chronic medications be retained.

Quantification of TWA levels allows physicians to track patients' responses to medications and cardiac rehabilitation.

A head-to-head comparison of the Spectral and MMA methods revealed similar hazard ratios, kappa statistics, and areas under the receiver-operator characteristic curve.

[15] Use of the spectral method for measuring Microvolt T-wave Alternans has been approved for reimbursement by Medicare, as well as major insurers such as Aetna, Cigna, and Humana.