The study is based on data from 768 patients who were candidates for Implantable cardioverter defibrillators (ICDs) at Christ Hospital and the Ohio Heart and Vascular Center in Cincinnati. Each patient received a test called microvolt T-wave alternans or MTWA, along with a battery of other tests, during their evaluation. Half of the patients went on to receive ICDs, although the MTWA test results were not used in the decision-making process. The patients' health and the causes of any deaths were tracked for up to three years.

In all, 67 percent of patients had positive or inconclusive MTWA test results. Of them, the patients who went on to receive an ICD were 55 percent less likely to die in the follow-up period than those who hadn't gotten an ICD. They were also 70 percent less likely to die suddenly due to a heart-rhythm disruption. But at the same time, the one-third of patients who had negative MTWA tests and then received ICDs were no less likely to die than those with similar test results who did not receive ICDs.

"This is the first study to demonstrate that a subset of patients who meet current criteria for defibrillator placement may not benefit at all from ICDs," says Paul Chan, M.D., M.Sc., senior author and a fellow in cardiovascular medicine at the U-M Medical School. "Use of the MTWA test could truly help us tell which ICD candidates will benefit most."

In all, the authors calculate, one life could be saved every two years for every nine ICDs implanted in people with positive or inconclusive MTWA results. But it would take 76 ICD implantations in people with negative MTWA tests to save one life every two years. The reductions in death risk were present even after the authors corrected for many other variables and differences between the two MTWA-positive and MTWA-negative groups.; Source: University of Michigan Health System