Test identifies best candidates for implanted cardiac defibrillator, screens out those not helped

Study shows one third of candidates are unlikely to benefit from ICD

Last year, about 170,000 people in North America had devices surgically implanted to stop potentially fatal arrhythmias. For many, these were life-saving, but for others they were unnecessary, uncomfortable, and sometimes dangerous. Now a new, noninvasive test may help determine which patients are most likely to benefit from the device, known as implantable cardiac defibrillator (ICD). A large, multicenter, NIH-sponsored study coordinated by Columbia University Medical Center researchers reported on the accuracy of the test was and was published in the latest issue of the Journal of the American College of Cardiology.

The test, known as the Microvolt T-wave Alternans (MTWA) test, measures the electrical activity in the heart while the patient is performing light exercise on a stationary bicycle or treadmill. It can detect an electrical signal that can identify a heart likely to generate a life-threatening rhythm disturbance, a signal too slight to be detected by the traditional electrocardiogram (ECG). The MWTA test will be most helpful for patients who are at risk but have not yet had a cardiac arrest. If an arrhythmia occurred in a patient who had an ICD, the device would deliver a pulse of electrical current through the heart in order to stop the potentially fatal arrhythmia.

“Until now, it’s been difficult to determine which patients need prophylactic ICDs and which are unlikely to be helped by them, but this noninvasive and inexpensive office-based test can identify up to a third of candidates for the devices who are not likely to benefit from them,” said J. Thomas Bigger, MD, professor of medicine and of pharmacology at Columbia University Medical Center, who conducted the research.

The study followed 549 patients from 11 North American clinical centers for two years following an MWTA test.

The MTWA test might also reduce healthcare expenses, since ICD implantation costs roughly $50,000 and the test costs about $400. But as doctors become more confident about accurately targeting which patients would be helped by the devices, the number of prophylactic implantations may increase.

The test does not have national coverage by Medicare intermediaries, but the Centers for Medicare and Medicaid Services (CMS) is currently reviewing its coverage policy for the MTWA test and is expected to make a decision on coverage in March.