Microvolt T-Wave Alternans (MTWA) refers to a subtle alternating pattern in the ECG. Extensive clinical studies have demonstrated that this pattern is associated with increased risk of sudden cardiac arrest. When the MTWA test is normal or negative, this indicates a very low risk.

MTWA tests may be administered in a physician’s office, hospital or outpatient clinic setting, in much the same way as a stress test. MTWA testing requires elevation of the heart rate for a short time. Patients typically walk on a treadmill for several minutes with a set of 14 electrodes on the torso: seven standard and seven high-resolution electrodes. Unlike stress testing, the heart rate is increased gradually and patients are not required to exercise until exhaustion. MTWA testing can also be conducted using pharmacologic agents or pacing to elevate the heart rate.