What is Microvolt T-Wave Alternans (MTWA)?
What is the MTWA test?
Why should I risk stratify my patients?
What does the clinical validation say about the reliability of MTWA testing?
Which patients should be MTWA tested?
Is the test reimbursed?
How do we measure Microvolt T-Wave Alternans?
What role does MTWA testing play in MADIT II and SCD-Heft patients?
What equipment do I need to perform a Microvolt T-Wave Alternans Test?
How is the test performed?
How long does an average test take?
How do I see the test results?
What do I do if my patient tests MTWA negative/normal?
What do I do with patients who test positive?
What do I do with patients who are indeterminate?

What is Microvolt T-Wave Alternans (MTWA)?
Microvolt T-Wave Alternans is a beat-to-beat fluctuation in the amplitude of the T-wave at a microvolt level. When detected this indicates the presence of a type of cellular metabolic activity that frequently leads to tachyarrhythmias. Microvolt T-Wave Alternans testing was cleared by the FDA for its ability to predict ventricular tachyarrhythmias and sudden cardiac death.
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What is the MTWA test?
The Microvolt T-Wave Alternans test is a risk stratification tool to help you determine your patient's risk of Sudden Cardiac Death. It is non-invasive, easy to perform diagnostic test clinically proven to identify patients at risk of Sudden Cardiac Death. The proprietary Analytic Spectral Method algorithm measures alternans to as small as a millionth of a volt and processes the data to determine each patient's risk profile. . Multiple prospective clinical trials demonstrate that a majority of patients from broad groups of at risk populations who test MTWA negative will likely live event-free for 12 to 24 months after their initial test.
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Why should I risk stratify my patients?
The CMS decision that now makes over 1,000,000 patients eligible for ICD therapy is one very good reason to risk stratify. Current studies^1,2 demonstrate that most patients who receive ICD therapy will not derive any benefit from their implant. With the proven negative predictive value of the MTWA testing, you have a tool that helps determine which patients have the lowest risk of Sudden Cardiac Death and are not likely to benefit from ICD therapy.
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What does the clinical validation say about the reliability of MTWA testing?
There is a compelling body of evidence that Microvolt T-Wave Alternans provides accurate negative prediction of VT and sudden cardiac death. Studies also show that the positive predictive value of MTWA testing is at least equivalent to that of an EP study. For a summary of the key clinical results, click here.
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Which patients should be MTWA tested?
Any patient eligible for ICD implant in primary or secondary prevention of Sudden Cardiac Death.
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Is the test reimbursed?
The procedure is reimbursed by Medicare and by some private insurers. For specific information about reimbursement in your area, click here.
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How do we measure Microvolt T-Wave Alternans?
Our technology measures Microvolt T-Wave Alternans non-invasively during routine exercise, pharmacological, or pacing using proprietary algorithms and signal processing techniques. The MTWA testing system includes a computer with proprietary software that can be configured for both hospital and office settings.
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What role does MTWA testing play in MADIT II and SCD-Heft patients?
In both MADIT II and SCD-Heft patient groups are now eligible for ICD therapy as a primary prevention treatment and are ideal candidates to be risk stratified by MTWA testing prior to referral to electrophysiologist. Patients in these groups who have a normal MTWA test are not likely to experience a sudden cardiac event for 1-2 years and therefore not likely to benefit from ICD therapy.
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What equipment do I need to perform a Microvolt T-Wave Alternans Test?
You need a product that measures T-wave alternans using the Analytic Spectral Method. The systems available from Cambridge Heart include CH2000 and the HearTwave® II System.
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How is the test performed?
Preparation for a Microvolt T-Wave Alternans test is the same as it is for an exercise stress test.
Fourteen Sensors - 7 Micro-V Alternans sensors and 7 standard electrodes are placed in the Frank-lead configuration. These electrodes are connected to the digital ECG amplifier that leads back to the Microvolt T-Wave Alternans enabled system.

At the beginning of the test, the patient is directed to begin walking on a treadmill to raise the heart rate. The exercise portion of the test will be approximately 8-10 minutes. Information will be collected for the Microvolt T-Wave Alternans Test while at rest, during exercise and at rest again.
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How long does an average test take?
Including electrode prep, an average test takes less than 30 minutes.
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How do I see the test results?
An automatic report is printed after the data have been processed by the MTWA proprietary algorithm. The report includes an interpretation of your patient's results which is classified as negative, positive, or indeterminate.
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What do I do if my patient tests MTWA negative/normal?
Studies demonstrate that in patients who have a normal MTWA test the risk of sudden cardiac death is very low. In fact, the negative predictive value of MTWA testing has been shown to be 98% accurate for follow-up periods of 12 -24 months in various clinical studies. Negative patients should be retested every 12 months as cardiac function can change over time.
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What do I do with patients who test positive?
Patients who test MTWA positive are at higher risk for Sudden Cardiac Death than those testing negative and should be referred to an electrophysiologist for further evaluation.
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What do I do with patients who are indeterminate?
Patients who have an indeterminate test result should be retested immediately. Studies indicate that over 50% of patients who initially test as indeterminate, become determinate if retested during the same session. If the indeterminacy is to due to an inability to achieve heart rate or dense ectopy, the patient should be considered at risk for SCD and referred on to an electrophysiologist.
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References