MINNEAPOLIS, Minnesota — Eight years ago, Marie Johnson was on her way to meet her husband Rob at a local community center. As Johnson pulled into the building, she noticed a body covered in a sheet — somebody had died.
That somebody was her husband.
The former Lockheed Martin vibrations engineer, who was studying to be a minister, suffered a fatal heart attack despite showing no obvious symptoms of coronary artery disease (CAD).
“It seemed incredible to me that there was no way to tell,” Johnson said.
Haunted by his death, Johnson, an engineer who now directs the University of Minnesota Medical Devices Fellowship program, is developing a low-cost acoustic device that primary care doctors can use to spot potential trouble.
The egg-shaped stethoscope system, which resembles a travel iron, records acoustic data originating from the fourth left intercostal space in the patient’s heart. Powered by a proprietary algorithm, special software crunches the information to determine whether the patient’s arteries are clogged with plaque. Such a condition, called stenosis, can lead to the kind of heart attack that killed Johnson’s husband.
Experts say Johnson, who founded AUM Cardiovascular, is on to something. LifeScience Alley recently named AUM Cardiovascular one of the state’s top medical device start-ups for 2009. The company, which received $1 million in seed funding from an undisclosed angel investor, hopes to begin clinical trials this year.
Despite its status as the top killer of Americans, coronary heart disease (CHD) is hard to predict, especially for patients who are asymptomatic. CHD caused one in five deaths in the United States in 2005, according to the American Heart Association. Among adults 20 years or older, people who suffer from CHD made up 21 percent (16.8 million) of all cardiovascular disease cases in 2006.
Normal screening methods at a primary care facility — measuring blood pressure and low-density liptoids (LDL) — are not good predictors of stenosis, said Mark Kroll, a former chief technology officer and senior vice president of the cardiac rhythm management division at St. Jude Medical Inc.
Studies show that scanning technologies like computer topography, magnetic resonance imaging and ultrasound can detect stenosis by measuring everything from thickness of artery walls to calcium deposits. But such technologies are expensive and payers in recent years have demanded stronger evidence of clinical benefits before they approve reimbursement. Besides, a primary care doctor is unlikely to refer asymptomatic patients to specialty clinics that offer these devices, Kroll said.
“So what is critically needed is something to screen for CAD that is as simple and inexpensive to use as a blood pressure unit so every clinic gets one,” said Kroll, an engineer whose work on shrinking implantable cardioverter defibrillators (ICDs) helped give birth to a $5 billion industry. “This is the promise of AUM. They appear to have the closest thing to the ideal primary clinic screening test for CAD. Compact, easy to operate, painless and requiring no injections.”
Johnson took her husband’s death particularly hard because she insists it was preventable. Nine months before he died, Johnson, an expert in auscultation, listened to Rob’s heart with a stethoscope and heard a “weird sound.” He went to a doctor, who assured them it was nothing.
As a post-doctoral fellow at 3M Cos., Johnson helped develop a digital stethoscope system that could detect heart murmurs. She decided to apply the same principles to artery blockage.
Johnson created an algorithm that could identify a specific acoustic signature associated with ischemia, or a lack of blood flow, in the proximal left anterior descending coronary artery (LAD). The LAD artery is commonly known as “The Widow Maker,” because if blocked, a patient will likely die of a massive heart attack.
Creating a robust sensor that could filter out excess noise proved tricky, Johnson said. She also had to design pattern recognition/data mining software that could quantify a patient’s risk of stenosis in a meaningful way. Based on the device’s reading, a primary care doctor can recommend lifestyle changes and/or refer patients to a cardiologist for further testing. Johnson’s device can easily upload the data to a widely available PDA like an iPhone.
In a 2006 study presented to the American Heart Association, Johnson and her team used the system on 57 patients who later underwent angiograms (X-rays of the arteries) at the University of Minnesota. All displayed signs of coronary artery disease. She then compared the data: Her system identified 100 percent of the patients with normal arteries and 66 percent of the patients the angiograms revealed to have LAD stenosis.
Some experts worry that patients could undergo too many tests, which could lead to false positives and emotional distress. For example a federal task force recently recommended that women should get mammograms beginning at age 50 instead of 40. The task force said women in their 40s are less likely to have breast cancer but could harm themselves both physically and emotionally through over-treatment.
But after what happened to her husband, Johnson says more testing is better than less.
“I’m okay with that,” she said.