A test that may better target those who will need ICDs

An Eden Prairie-based start-up has developed a test that it says can more accurately predict whether a patient might die of a sudden heart attack and thus needs an implantable cardioverter defibrillator (ICD).

In a study presented to the Heart Rhythm Society conference in San Francisco last month, Harbinger Medical Inc. said the test, called the Wedensky Modulation Index, predicted 80 percent of the life-threatening irregular heartbeats experienced by 300 patients who had previously suffered heart attacks. The study was performed by Dr. Peter Brady, a cardiologist at the Mayo Clinic in Rochester.

The test could allow doctors to better determine who needs an ICD, a stopwatch-size device implanted under the collarbone that shocks an errantly beating heart back into rhythm. Medtronic Inc. of Fridley, St. Jude Medical Inc. of Little Canada and Boston Scientific Inc., which has major operations in Arden Hills, are all major ICD manufacturers.

"People are looking for more accurate ID of patients who need an ICD," according to Harbinger CEO Harold Hoium.

"You give the physicians more tools to make a good decision."

Harbinger hopes to sell the test, which has yet to receive Medicare reimbursement, by early 2009. It will cost about $200 to $300. The company is backed by NeoMed Management Ltd., a $200 million European venture capital firm that invests in health care and life sciences companies.

Mark Kroll, a former top executive at St. Jude Medical's cardiac rhythm management division; Marshall Stanton, a Medtronic vice president; and Jim Knoblach, a former chairman of the Minnesota House Committee on Ways and Means, sit on the board of directors. But one expert says that the Harbinger study, while "intriguing," was too small to reach any definite conclusions about the technology.

"To tell you the truth, I thought the data was kind of underwhelming," said Dr. Mike Peterson, a cardiologist at St. Paul Heart Clinic. Still, the study "was a necessary first step" for the company, he said.

Heart attacks can permanently damage hearts, leaving scar tissue. Such damage can cause irregular heartbeats and subsequent fatal heart attacks. While ICDs are highly effective in thwarting sudden cardiac death -- which kills about 300,000 to 400,000 people a year in the United States -- knowing which patients should receive the expensive devices has long vexed doctors. According to industry estimates, 30 percent of patients who qualify for an ICD never get the implant. Conversely, a high number of patients who have ICDs don't need them and sometimes receive painful electric shocks.

Identifying the right patients

"There's a struggle to identify the right patient population," said Dr. Quan Pham, an interventional electrophysiologist at Fairview Southdale Hospital. "We cast a wide net to catch a few fish. It's hard to predict which people will die suddenly."

Ross Meisner, managing partner at Dymedex Consulting, said that effective testing could reduce overall ICD sales. The tradeoff is that "doctors will feel more confident that a patient really needs an ICD," said Meisner, who is advising Harbinger.

To screen patients for an ICD, most doctors calculate what's called the ejection fraction (EF) -- the heart's ability to pump blood. A patient with an EF rate of less than 35 percent is considered at high risk for serious arrhythmia. But EF alone is far from a perfect indicator, Pham said.

Some companies believe that arrhythmia is the result of an electrical flaw in a person's heart. Cambridge Heart Inc., based in Bedford, Mass., developed a test called the Microvolt T-Wave Alternans, which measures electrical activity in the heart while the patient is exercising. The system can detect an electrical signal in the heart that might generate a rhythm disturbance invisible to a routine electrocardiogram. St. Jude Medical, a major investor in Cambridge Health, is selling the technology to cardiologists and electrophysiologists in North America.

Harbinger's system operates on similar principles, although company officials say it covers more of the heart, takes only 20 minutes and patients can lie still. Kroll, who helped invent the Harbinger technology, said he wanted to create a device that could measure the "electric echo" of the heart in the same way an electrocardiogram uses ultrasound to detect abnormalities such as heart murmurs.

How it works

Here's how the Wedensky Modulation (named for late Russian neurophysiologist Nikolai Wedensky) works: The system stimulates a diseased heart using low-voltage electricity and then compares the resulting heartbeat to that of a healthy heart. A heart suffering from dangerous arrhythmia shows little reaction to the stimulation, while a healthy heart demonstrates a dramatic change.

Harbinger tested the system on 300 patients around the world who had suffered heart attacks and were implanted with ICDs. The company then predicted which patients would suffer a serious irregular heartbeat that would trigger the device. After six and 12 months, Harbinger said it correctly predicted 80 percent of those cases.

Moreover, "it turns out that using EF to identify patients of risk was quite poor," Hoium said.

Pham, the electrophysiologist, is skeptical. Although he was not familiar with Harbinger's system, Pham said that there is still no evidence that proves a direct correlation between a heart's electrical signals and arrhythmia. A number of factors can cause disruptions in the signal, he said.

Indeed, even Harbinger officials say they cannot explain why Wedensky Modulation works, only that it seems to be an excellent predictor of sudden cardiac death.

Peterson of St. Paul Heart Clinic says that understanding the link between irregular heartbeats and electricity would help persuade doctors to adopt technology such as Wedensky and use it more accurately. Although Cambridge Heart's T-Wave test has been around for years (Medicare reimburses the procedure), many doctors don't use it because the test is cumbersome and patients are responding to better drug treatments, he said.

"The jury is still out," Pham said. The technology may "add some value, but I would not base my clinical decisions on it."

Thomas Lee • 612-673-7744