T-Wave Alternans (TWA)

Microvolt T-wave alternans (MTWA) is a non-invasive heart test that can identify patients who are at increased risk of sudden cardiac death. It is most often used in patients who have had myocardial infarctions (heart attacks) or other heart damage to see if they are at high risk of developing a potentially lethal cardiac arrhythmia. Those who are found to be at high risk may benefit from the placement of a defibrillator device which can stop an arrhythmia and save the patient's life.

The TWA test uses an electrocardiogram (ECG) measurement of the heart's electrical conduction. The test looks for the presence of repolarization alternans (T-wave alternans), which is variation in the vector and amplitude of the T-wave component of the EKG. The amount of variation is small, on the order of microvolts, so sensitive digital signal processing techniques are required to detect TWA. It requires a low level exercise to increase the heart rate slightly so the test may be more accurate.