Originally Released: October 25, 1999
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The University of Maryland Medical Center is using a non-invasive diagnostic tool to help identify patients at risk of life threatening arrhythmia (rapid heartbeat) and sudden cardiac death. The tool, called the Alternans Test, works like a "super stress test" by measuring subtle beat-to-beat fluctuations in a person's heartbeat called T-wave alternans. Patients who test positive for T-wave alternans are at a significant risk of sudden cardiac death.
"Sudden cardiac death kills more than 300,000 people each year," says Michael Gold, M.D., Ph.D., director of cardiac electrophysiology at the University of Maryland Medical Center and associate professor at the University of Maryland School of Medicine. "The Alternans Test is a very simple, non-invasive technique that can quickly identify patients at risk of sudden cardiac death. That information helps us to more easily determine which patients will benefit from an implanted defibrillator to regulate heartbeats."
A regular exercise stress test can identify patients at risk of heart disease but is not able to detect patients with arrhythmic heart disease or "electrical problems" that can lead to sudden cardiac death. Patients at risk of sudden cardiac death are those who have had a previous heart attack or some form of heart damage.
The Alternans Test measures tiny heartbeat variations -- as small as one millionth of a volt -- by using specially designed, high-resolution electrodes placed on the patient's chest during a typical treadmill or bicycle exercise stress test. The information is fed into a cart-mounted computer with specific software and output devices.
Currently, the risk of arrhythmia is evaluated through an electrophysiology (EP) test. That procedure takes up to three hours and is invasive. Catheters are threaded into a major vein, typically through the groin, and then into the heart. Because of the risks and costs associated with invasive testing, only a small fraction of people at high risk are referred for the diagnostic EP test each year.
"The availability of this non-invasive test to predict life-threatening arrhythmia in high-risk patients will lead to earlier intervention and prevention of sudden cardiac death in more patients," says Dr. Gold who was one of the first doctors to test the new diagnostic tool. "The traditional EP test is still being used but the Alternans Test is a good tool to screen all high risk patients."
The treatment option for people who are found to be at risk of sudden cardiac death is to have a defibrillator implanted that will automatically shock the heart back into normal rhythm.
The T-wave Alternans Test is made by Cambridge Heart in Bedford, Massachusetts.
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