Test identifies people at cardiac risk.

Measurement of an electrical abnormality in the heart aids doctors in determining who is most at risk for cardiac arrest, according to a new study.

Computers can detect the abnormality, called T-wave alternans, during an electrocardiogram, a recording of the heart's electrical activity. Since T-wave alternans often precedes sudden cardiac arrest, researchers have suggested that it could be used to decide which patients need implanted defibrillators (SN: 9/23/06, p. 202). Those devices sit inside the chest and deliver a therapeutic shock when the heart needs it. However, many patients get defibrillators unnecessarily.

Now, doctors have completed the first systematic test of using T-wave alternans for making decisions about implanting defibrillators. David S. Rosenbaum of Case Western Reserve University's MetroHealth Campus in Cleveland and his collaborators made the measurement on 566 heart patients. The doctors implanted defibrillators in all 401 volunteers who had abnormal T-wave patterns, but they opted not to use devices in the remaining volunteers unless other tests overwhelmingly indicated the need.

Over 1 year, patients with the abnormal T-wave patterns were about twice as likely as other patients to have a cardiac event that necessitated a defibrillator.

T-wave testing combined with other tests could reduce unnecessary use of defibrillators by as much as 40 percent, Rosenbaum says.--B.H.