February 1 , 2009
FVCC Introduces T-Wave Alternans Testing for Evaluation of Risk for Sudden Cardiac Death
What is sudden cardiac arrest?
Sudden cardiac arrest (SCA) is a failure in the heart's electrical system in which the heart stops suddenly and without warning. In the US, over 400,000 adults die each year from sudden cardiac arrest.
How is sudden cardiac arrest different from a heart attack?
Sudden cardiac arrest is a malfunction of the heart's electrical system while a heart attack, also called a myocardial infarction, results when a part of the heart is starved of oxygen - called ischemia. This happens when a clot or blockage obstructs one of the arteries that supply blood to the heart. What causes sudden cardiac arrest? Sudden cardiac arrest is caused by life-threatening arrhythmias. One of the most common arrhythmias is called ventricular fibrillation. This is when the lower chambers of the heart quiver and are incapable of pumping blood out to the rest of the body. A victim of sudden cardiac arrest immediately stops breathing, has little or no detectable pulse and, with no intervention, will die within minutes. Most people who suffer from a ventricular arrhythmia have an underlying electrical disorder of the heart that can usually be detected by the Microvolt T-Wave Alternans Test.
Who is at risk for sudden cardiac arrest?
Any one can be a victim of sudden cardiac arrest but some people are more at risk. These are people with a previous history of cardiac arrest or life threatening ventricular arrhythmias, documented heart disease and symptoms of possible arrhythmias such as fainting. Others at elevated risk include patients with congestive heart failure, prior heart attack, and a family history of sudden death and coronary artery disease.
What tests can I have to find out if I am at risk for sudden cardiac arrest?
Prior to the Cambridge Heart Microvolt T-Wave Alternans (MTWA) Test, there was no accurate, non-invasive way to predict a patient's risk for life-threatening arrhythmia. Other non-invasive tests such as the conventional exercise stress test and echocardiography do not specifically identify risk of ventricular arrhythmia. Studies have shown that the MTWA test has comparable accuracy to the electrophysiology (EP) test - an invasive procedure performed in the hospital.
About the Microvolt T-Wave Alternans Test
What is Microvolt T-Wave Alternans?
A T-wave is part of your heart's ECG wave. Microvolt T-wave alternans are slight differences from one beat to the next in that T-wave. When visible on the ECG, these alternations or alternans are associated with an increased likelihood of ventricular arrhythmia (abnormal heartbeats). Unfortunately, the T-wave alternations are not normally visible to the naked eye when a routine ECG is performed.
What is a Microvolt T-Wave Alternans Test?
The Microvolt T-Wave Alternans test permits measurement of the T-waves at a millionth of a volt level, allowing your doctor to evaluate alternations of the T-wave that may have otherwise been missed by a less sophisticated test. The MTWA test is a non-invasive procedure usually done in your physician's office to help your doctor identify if you are at risk of life threatening heart rhythm disturbances that could lead to sudden cardiac death.
Why is Microvolt T-Wave Alternans testing necessary?
If you are scheduled for a MTWA test, your doctor has determined you might be at risk for a sudden cardiac episode. Most people who suffer a cardiac arrest episode have an underlying, pre-identifiable, electrical disorder that puts them at risk. Microvolt T-Wave Alternans Testing helps identify which people are at risk for sudden cardiac death.
How is the test performed?
Preparation for a Microvolt T-Wave Alternans test is the same as it is for an exercise stress test. A nurse or technologist will apply sensors to multiple spots on your chest and back. These electrodes are connected to a wire that leads back to the Microvolt T-Wave Alternans equipment.
At the beginning of the test, the nurse or technologist will ask you to begin walking on a treadmill to raise your 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 you are at rest, as you walk on the treadmill and at rest again.
What happens during the test?
In order to collect Microvolt T-Wave Alternans information, your heart rate must be raised, although not to the extent of a stress test, for several minutes. The heart rate increase is achieved by walking on a treadmill. If you are unable to walk the treadmill, your physician may use certain drugs to increase your heart rate to complete the MTWA test.
What happens to my test results?
Your doctor will interpret the test results and let you know if your risk is low or if you may need to see a specialist for further evaluation.
T-Wave Alternans Testing is available at our FVCC-Highland location.