T-wave Alternans
Why is the doctor performing this test?
Like Signal Averaged ECG described in the previous section, T-wave alternans is another way to evaluate the heart's functioning by viewing its electrical activity. It is similar to a standard Electrocardiogram (ECG), but provides greater in-depth information by collecting many heart beats and analyzing them for specific changes that can occur in diseased heart muscle.
What is the test?
Similar to an ECG (See ECG for information on a standard electrocardiogram), the T-wave Alternans test is a painless, non-invasive test, with electrodes placed on the skin. Electrical activity is recorded while the patient gently exercises, typically either while walking on a treadmill, riding a stationary bicycle, or by simulation of exercise with a medication in patients who cannot exercise. The objective is to get the patient's heart rate up to approximately 110 beats per minute. The electrical activity is processed by a T-wave Alternans computer with the software evaluating beat-to-beat changes that occur at a level too subtle to be seen by the human eye alone. The presence of this alternating pattern identifies patients at a higher risk for having life-threatening arrhythmias in which case the patient would require further evaluation, typically with an EP Study.
A T-wave alternans test is sometimes used in the following settings:
- To determine risk for ventricular arrhythmia following heart surgery or a heart attack.
- To determine risk for ventricular arrhythmia in patients with weakening of the heart muscle ("cardiomyopathy")
- To determine the cause of fainting (called syncope).
Where is the test performed?
A T-wave Alternans test is typically done in the Non-Invasive Cardiology Testing Center.
How long does this test take?
A standard ECG takes about 5 minutes; a T-wave Alternans test takes a bit longer, usually about 20 minutes.
