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A medical game changer

Marie Guion Johnson, Ph.D., founder of AUM Cardiovascular, also works as an adjunct assistant professor of biomedical engineering at the University. (Photo: Scott Streble)

New device shows early promise for detecting heart disease

It’s taken personal tragedy, years of research, and a mysterious late-night epiphany for Marie Guion Johnson, Ph.D., to develop a promising new medical device that can detect coronary-artery blockage. Her invention, called the CADence™, is a noninvasive handheld tool that she hopes eventually will be used as a functional test for people at high risk of developing heart disease, the leading cause of death in the United States.

The story of the CADence stretches back more than a decade, when Johnson, a doctoral student at the University of Minnesota, was working with a powerful electronic stethoscope to develop a computer model for enhancing auscultation (listening to heart sounds). Her husband, Robert Guion, was a convenient, good-natured test subject, but when Johnson listened to his heart, she heard an anomaly. Concerned, Guion followed up with a standard stress test. When the results showed nothing out of the ordinary, Johnson chalked it up to her lack of medical training, and the couple thought nothing more about it.

Just nine months later, however, Guion, 41, was dead of a “widow-maker” heart attack—the result of a sudden and complete blockage in his left anterior descending artery.

Johnson, mother of a 4-year-old daughter and newborn son, was devastated. But she was also determined to discover what had happened to her seemingly healthy husband, and she pored over his recorded heart signals looking for clues.

“I was sitting at my computer at three o’clock in the morning,” she says of her eureka moment, “and I’m looking at this data, and it was like I heard a whisper: ‘There it is. That’s it.’”

It turned out that the sound she’d detected in Guion’s heart was a little-known Dock’s murmur. The cause: blockage in the left anterior descending coronary artery.

Battling heart disease became Johnson’s mission. After finishing three postdoctoral fellowships, she returned to the University of Minnesota to create and lead the Medical Devices Fellows Program until 2010, when she left to start her own company, AUM Cardiovascular. It was there that she developed the CADence, which picks up subsonic turbulence in heart sounds and converts it into digital data that can be analyzed using a mathematical algorithm designed to identify blockages.

Chief of clinical cardiology Robert F. Wilson, M.D., lauds the CADence device as both risk-free and cost-effective. (Photo: Richard Anderson)

Robert F. Wilson, M.D., chief of clinical cardiology at the University of Minnesota and principal investigator for the initial CADence study, has called the device “a game changer.” According to Wilson, the results of his pilot study—which were presented in August 2012 at the European Society of Cardiology in Munich—show the CADence to be as accurate as a standard EKG stress test but potentially more useful.

“You can see the obvious benefits,” he says. “There’s absolutely no risk, and the cost is substantially less than a stress test both to the health-care system and to the patient.”

For the patient, a CADence test is painless and brief. The sleek, palm-sized device is placed on the chest to monitor each of the four main coronary arteries, which takes about two minutes. A Wi-Fi chip in the device sends the information via the Internet to AUM, where it’s analyzed; the report is then sent directly to the doctor’s computer or tablet.

The next step for the device is an FDA market-clearance study, which could take place as soon as this December. Wilson will be one of the primary investigators for that trial as well.

Johnson, also an adjunct assistant professor of biomedical engineering at the University of Minnesota, is thrilled with the early promise of the CADence, but definitely not ready to rest on her laurels.

“My goal is to eradicate needless death due to coronary artery disease,” she says firmly, “and to reduce the number of widows and widowers, and kids who have to grow up without their mom or dad.”

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