The Ohio State University Wexner Medical Center employs eight nurses whose only job is to read the electronic transmissions flowing from thousands of implanted heart devices living in their patients' chests.
Like health-data workers across the U.S., the nurses at the Columbus, Ohio medical center scan the transmissions every day for signs of problems, like atrial fibrillation. Lately, though, the team was drowning in bad data thrown off by a popular implantable heart monitor, Medtronic's industry-leading Reveal Linq implantable loop recorder.
According to study results published online last month in the peer-reviewed Heart Rhythm journal, the team analyzed data on 559 consecutive Ohio State patients and found that between 46% and 86% of the health alerts sent by their implantable Medtronic heart monitors were false. Each false positive required between 30 and 45 minutes of clinicians' time, and created a risk that patients would get the wrong treatment, like blood thinners they don't need -- especially during periods when physicians who support the data nurses were deluged with other cases.
Dr. Muhammad Afzal, corresponding author of the Heart Rhythm paper, said the number of false-positives using devices with factory settings was "significant." Medtronic, which is run from offices in Fridley, stressed that the minimally invasive Linq device can be programmed by a doctor to tone down the detection of certain heart signals that may not be relevant to a particular patient, reducing time spent on false-positive transmissions.
Implantable heart monitors accounted for nearly $1 billion in U.S. sales last year and continue to grow, with Medtronic's Reveal Linq leading by a wide margin a market that includes monitors made by Abbott Laboratories and Biotronik, said Sean Messenger, a med-tech industry analyst with Decision Resources Group.
Smaller than a AAA battery, the Linq retails for slightly less than $5,000 to hospitals, analysts say, which can double that price or more in its bills to insurers.
The battery-powered devices can monitor for irregular heartbeats continuously for at least three years, making them more comprehensive than other forms of temporary heart monitors, like Holter monitors and temporary cardiac patches, which can read and record data for 24 hours to 14 days.
The Linq is considered a single-lead electrocardiogram device, like the AliveCor Kardia mobile device, and it generates a single electrocardiogram "tracing" of heart activity, like the ECG app on the Apple Watch Series 4. Doctors say that implantable cardiac monitors are considered more accurate than non-implantable devices since they take their readings closer to the source and don't need recharging, among other factors.
Medtronic said the Linq is effective at diagnosing problems that would have been undiagnosed otherwise. A 2017 report in JAMA Cardiology found that 40% of 385 patients who received the device at one of 57 different hospitals had episodes of atrial fibrillation detected after 30 months, with a median time-to-detection of 123 days.
Kentucky cardiologist Dr. John Mandrola, a frequent industry commentator who did not take part in the Ohio State study, said the false-positive rates reported in the recent Heart Rhythm article appeared to be "super high," especially for a device bearing a medical-grade price tag.