Frequently Asked Questions

About Sudden Cardiac Arrest

What is Sudden Cardiac Arrest?

Sudden cardiac arrest (SCA) occurs abruptly and without warning when the heart’s electrical system malfunctions and blood cannot be pumped to the rest of the body. SCA is a leading cause of death in the United States, accounting for an estimated 325,000 deaths each year – more than stroke, lung cancer and breast cancer combined.
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How is sudden cardiac arrest different from a heart attack?

A heart attack, or myocardial infarction, occurs when a blockage in a blood vessel interrupts the flow of oxygen-rich blood to the heart, causing the heart muscle to be damaged. Symptoms of a heart attack may include chest discomfort, shortness of breath, light-headedness or a cold sweat.

Sudden cardiac arrest refers to an abrupt malfunction in the heart’s electrical system which is often the result of an abnormal heart rhythm (arrhythmia) called ventricular fibrillation. During cardiac arrest a victim suddenly loses consciousness, stops normal breathing and loses pulse and blood pressure.
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Who is at risk for sudden cardiac arrest?

Risk factors for SCA include prior heart attack, coronary artery disease, a weak heart muscle (low ejection fraction), congestive heart failure, fainting (syncope) and family history of SCA.
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What tests can I have to find out if I am at risk for sudden cardiac arrest?

Patients at risk for SCA may undergo non-invasive diagnostic testing including electrocardiogram (ECG), Holter monitoring or cardiac ultrasound. An electrophysiology study (EPS) is an invasive test that may be used to assess arrhythmic vulnerability in some patients.

Microvolt T-Wave Alternans (MTWA) testing is a non-invasive test that detects a subtle electrical abnormality in the heart that is associated with SCA risk. The MTWA test is similar to a stress test and is often conducted with low-level exercise on a treadmill.
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About the Microvolt T-Wave
Alternans Test

What is Microvolt T-Wave Alternans?

T-wave alternans is an electrical abnormality in the heart that is associated with SCA risk. Microvolt T-Wave Alternans (MTWA) refers to a subtle alternating pattern in the T-wave portion of the surface electrocardiogram that is not visible to the human eye and is not detectable on a standard ECG.
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What is a Microvolt T-Wave Alternans Test?

MTWA tests may be administered in a physician’s office, hospital or outpatient clinic setting, in much the same way as a stress test. Patients typically walk on a treadmill for 5-10 minutes with a set of 14 electrodes on the torso. 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.
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Why is Microvolt T-Wave Alternans testing necessary?

If you are scheduled for a MTWA test, your doctor has determined that you might be at risk for a sudden cardiac episode. Microvolt T-Wave Alternans Testing helps identify which people are at highest and lowest risk for SCA.
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How is the MTWA test performed?

MTWA tests may be administered in a physician’s office, hospital or outpatient clinic setting, in much the same way as a stress test. Electrodes are applied to the patient’s torso which are connected to wires that lead back to the MTWA system. Patients are then asked to walk on a treadmill for 5-10 minutes in order to gradually elevate the heart rate. Once the required data is collected, the patient will be asked to rest for several minutes after which the electrodes are removed and the test is complete.
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What should I do to prepare for an MTWA test?

Generally, you should wear comfortable clothing for walking on treadmill. Your physician may ask you to withhold certain medications on the day or morning prior to the test. Consult your physician for any pre-test instructions.
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What happens to my test results?

Your doctor will interpret the test results and let you know if you may need further evaluation.
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Where can I get a Microvolt T-Wave Alternans Test?

Click here to request information about testing facilities near you.
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