Studies Confirm T-wave Alternans Test as Predictor
of Sudden Cardiac Arrest

	May 12, 1999 - Cambridge Heart Inc, today 
announced that several studies prove that T-wave 
alternans testing is a very good tool for diagnosing 
patients at risk of sudden cardiac arrest (SCA).
	These studies identify patient groups for 
which the Alternans Test is good. The Alternans Test
was cleared by the FDA on April 13, 1999. It is the 
only NON-INVASIVE test approved to identify patients
at risk of heart rhythm problems that may cause 
sudden cardiac arrest.
	One study shows that the Alternans Test can 
predict arrhythmias that cause sudden cardiac arrest
in patients with non-ischemic dilated cardiomyopathy 
(DCM). No other test has proved effective in 
predicting sudden cardiac death in these patients. 
	Another study shows promising results in a 
rare congenital disease called arrhythmogenic right 
ventricular cardiomyopathy.
	 A third study shows that the new test is a
better predictor of a positive EPS and of cardiac 
events than signal-averaged ECG. These tests are 
described at the end of this article.

About Sudden Cardiac Arrest and the Alternans Test

	SCA is caused by ventricular arrhythmia, an 
abnormality in the beating pattern of the heart, 
resulting in changes in the rate and frequency of
electrical impulses in the ventricles. SCA kills
about 300,000 people a year in the USA.
	The Alternans Test works like a "super stress
test." It measures extremely subtle beat-to-beat 
changes in a person's heartbeat called T-wave 
alternans. T-wave alternans is not visible on the
electrocardiograms used with ordinary exercise stress 
tests. These tiny heartbeat changes are detected 
during a treadmill or bicycle stress test by specially
designed, high-resolution electrodes on a patient's 
chest. Cambridge Heart Inc is based in Bedford, Mass.

The studies presented at the Electrophysiology
conference include:

1) Exercise Induced Microvolt Level T-wave Alternans 
Identifies Patients with Non-Ischemic Dilated 
Cardiomyopathy at High Risk of Ventricular 
Tachyarrhythmic Events, by Thomas Klingenheben, MD.
	It studied 56 patients with non-ischemic DCM.
Other tests have not been able to predict the risk of 
ventricular arrhythmic events very well. This 
concludes that the T-wave Alternans Test seems to 
identify DCM patients at high risk of VTE.

2) T-wave Alternans Predicts Arrhythmia Vulnerability
in Patients with Ischemic Cardiomyopathy, by Karen 
MacMurdy, MD.
	The researchers studied 87 patients with 
ischemic heart disease who had low EF and were 
referred for EP testing. Data show that T-wave 
alternans testing is an accurate predictor of risk of
Sudden Cardiac Arrest in patients with ischemic heart
disease and poor heart function. One implication of 
this study is that T-wave alternans testing may help 
identify patients who need an ICD.

3) Microvolt T-wave Alternans in Patients with 
Arrhythmogenic Right Ventricular Cardiomyopathy and 
Dilated Cardiomyopathy, by Yee Guan Yap, MRCP.
	The researchers did T-wave alternans testing on
48 patients with DCM and 13 patients with a rare 
congenital disease called ARVC. The study found that 
patients with DCM or ARVC have higher rates of positive
T-wave alternans results. The implication is that a 
positive T-wave alternans result may help cardiologists
identify patients with undiagnosed DCM or ARVC.

4) A Comparison of T-wave Alternans and Signal Averaged
Electrocardiography in Predicting Outcome of 
Electrophysiology Testing, by Daniel Bloomfield, MD.
	The researchers examined results from 103 
patients who had T-wave Alternans, ECG and EP tests. 
They found that T-wave alternans is a non-invasive 
predictor of a positive EP test, which in turn is a 
predictor of Sudden Cardiac Arrest. Further, a 
positive T-wave alternans result predicts a positive 
EP test better than signal-averaged ECG.