AUM Cardiovascular, based in Northfield, announced Tuesday that it received approval from the U.S. Food and Drug Administration to start selling its handheld digital stethoscope.

The non-invasive CADence device can detect markers associated with congestive heart failure and obstructive coronary artery disease. It also detects physiological and pathological heart murmurs.

It’s been six years in the making for company founder Marie Johnson, who began her work on the device following the death of her first husband in 2002. Her husband died of a heart attack as Johnson worked with 3M scientists to develop a computerized stethoscope at the time.

In 2009, Johnson left the academic world — where she completed her engineering degree and then went on to study in Italy and at Stanford University before ending up at the University of Minnesota with a Ph.D. — to start AUM Cardiovascular.

Two months into her third year of heading a think tank at the University of Minnesota, similar to the one she was a part of at Stanford, Johnson took the patent for her CADence device and started the virtual company in an outbuilding on her land just south of Northfield.

Johnson found out the device received approval from the FDA last Friday night while on vacation with her family in Idaho.

“I almost didn’t open [the email],” she said.

The device is already available to use in Europe, Canada, Australia, Japan and the Philippines and records sounds from a patient’s heart. A proprietary algorithm and software presents the data recorded in a physician’s report that becomes available in about 15 minutes after the device has been placed at four sites around the heart for 20 seconds each time.

The report allows physicians to determine a patient’s cardiovascular health, which is helpful because stenosis is difficult to detect for primary care doctors since patients typically don’t exhibit symptoms.

Johnson discovered a frequency signature with an electronic stethoscope that captured evidence of arterial blockages. The frequency signature linked to heart disease is caused by turbulence in the artery, as the blood flows around obstructions. The flow through a healthy blood vessel has little to no turbulence.

The CADence device is a disruptive technology that performs just as well as a nuclear stress test at a significantly lower cost and can be used by a certified medical assistant. A nuclear stress test typically measures blood flow to the heart at periods of rest and exertion. It also may involve an injection of radioactive dye into the bloodstream to detect any blockages.

Cardiovascular diseases are the leading cause of global mortality, accounting 30 percent of all deaths, according to the World Health Organization.

The CADence device has been used on 1,807 patients to date, according to the company. It costs around $100 to use the device for testing and the low cost makes it an attractive option for patients who may have to pay out of pocket. A nuclear stress test can range between $1,000 to $13,000, Johnson said, and can be tough for patients to find a specialist in their area to perform the test.

The device costs $4,999 and AUM Cardiovascular will use an original equipment manufacturer to produce the device.

“The CADence system has the potential to dramatically enhance our ability to rule-out significant coronary artery disease and efficiently triage patients needing additional testing,” said Dr. Jay Thomas, an interventional cardiologist at Harbor-UCLA Medical Center in Los Angeles, who oversaw the study in a press release.

Johnson started the company in 2011 and moved to Northfield in 2013. Two years later she moved the company to its location at 1405 Heritage Dr., Suite 100.

“CADence is an exciting example of how novel technology will revolutionize patient care,” Thomas said in a press release. “It is a rapid, cost-effective, radiation-free way to evaluate selected patients with chest pain. The need for something like CADence is quite obvious considering how we have managed chest pain testing for the last 20 years.”

MPR contributed to this report. You can listen to MPR News at 91.1 FM or online at

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