New Stress Test Predicts Heart Attack Risk

	April 14, 1999 - A new way to quickly predict 
which patients are at risk of heart attack has been 
approved. It is a non-surgical exam that is essentially 
a super stress test. The FDA ruled Tuesday that the 
"Alternans" test is the diagnostic equivalent of an EPS.
	It works by enhancing an electrocardiogram. 
Patients taking a standard EKG-monitored treadmill test 
have special electrodes placed on their chests. The 
Alternans system then measures subtle, unusual heartbeats
that indicate patients may be at risk of ventricular 
fibrillation, a lethal irregular heartbeat.
	About 350,000 Americans each year have heart 
attacks caused by this type arrhythmia. By finding who is 
at high risk, the patient might receive an ICD, a device 
that automatically jump-starts a heart going into 
arrhythmia. Most patients identified as needing ICDs 
were those revived by paramedics after heart attack - 
about 10-15% of arrhythmia victims.
	The Alternans test "has extraordinary 
potential for impacting the problem of sudden death," 
said Dr. David Rosenbaum, who helped discover that 
T-wave alternans signals may predict future heart 
attack.
	About 9 million people a year take treadmill-
style stress tests to diagnose their risk for clogged 
arteries, which cause most heart disease. But irregular 
heartbeats aren't caused by clogged arteries - they 
happen when the heart's electrical system doesn't work 
right.
	A regular stress test doesn't diagnose that risk.
The new device enhances the stress test to do so. The 
signals reflect abnormalities in how individual heart 
cells recover after relaying a heartbeat's electrical 
impulse, Rosenbaum says in the journal, Circulation. If 
the cells' voltage oscillates, a chain reaction can be 
started that ends in a deadly irregular heartbeat.
	Studies suggest that only 18% of heart patients 
who have T-wave alternans are alive 20 months later, 
while 95% of heart patients without the abnormality live 
that long. Electrophysiology testing, where electrodes 
are surgically put onto the heart, can detect high-risk 
patients but that is expensive.
	The Alternans test is equivalent to the surgical 
test but DOES NOT AUTOMATICALLY IDENTIFY AT-RISK PATIENTS, 
cautioned FDA's Dr. Dan Spyker. Specially trained 
cardiologists must read the machine's T-wave measurements 
to decide each patient's risk.
	Patients must be healthy enough to exercise at 
70% of their maximum heart rate during the treadmill test.
The Alternans test itself poses no risk to patients. The 
hope is that a non-invasive test will help doctors detect 
more of the people at risk in time to protect them. The 
big question is who should be tested.
	Half of heart attack victims have no previous 
history of irregular heartbeat or heart disease, yet 
testing everyone who gets a treadmill exam would be 
exorbitant. Those tested first will probably be heart 
attack survivors who have additional serious heart problems
like heart failure.
	The test should add about $100 to a conventional 
treadmill test, says the manufacturer of the device.

JON'S NOTE: An EPS allows anti-arrhyhtmia drug testing and
other treatments at the time of the test, which the new 
test does not, so it is not the equivalent of an EPS, 
only the DIAGNOSTIC equivalent.