FDA letter to medical device maker iRhythm is warning for industry

Jan 15, 2024

By Lizzy Lawrence June 9, 2023

Heart monitoring company iRhythm is in hot water with the Food and Drug Administration, which issued a stern warning letter to the device maker this week for marketing its product for "high risk" patients and changing its algorithm without seeking the FDA's permission.

The letter highlights FDA's growing scrutiny of digital health and patient monitoring tools — as well as the grave impacts even small device glitches can have on patients.

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"Many developers consider the ease with which they can make changes to their software as a free pass, if you will," said Jason Brooke, a medical device attorney and quality adviser. "This is a reminder that that's not a free pass."

iRhythm sells a wearable monitor, called the Zio AT system, that detects irregular heartbeats for up to two weeks. Its monitors do not present this data in real-time, so they are not intended for patients in critical care. But according to the FDA, iRhythm told customers that its devices provided "near real-time monitoring" and can be used for "high-risk patients."

Brooke said this type of transgression is common in the medical device space. He calls it "intended use creep," in which companies exaggerate their use cases in promotional materials.

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"You get market authorization from the FDA, and everyone gets really excited," Brooke said. "And then of course, the marketing and sales people go gangbusters in trying to promote the product."

iRhythm also made changes to its hardware and to the algorithm it uses to detect cardiac abnormalities without running them by the FDA. The FDA first raised its concerns after an agency investigation in August 2022. The company responded to the FDA's various concerns with seven separate letters. The FDA wasn't satisfied and instead issued the warning letter.

"Changes to the [redacted] algorithm can impact the accuracy of the detected arrhythmias, and testing would be needed to support that the algorithm's performance is unaffected by the change," the FDA wrote in its letter.

The FDA also slammed the company for not adequately informing doctors and patients about its device's transmission limit. iRhythm's monitor can automatically detect up to 500 arrhythmias. After that, the device must be replaced. The FDA said iRhythm did not make this limitation clear — with serious consequences.

"Our inspection found a significant number of complaints regarding this issue, which revealed two deaths as well as significant [arrhythmias] that were not reported to physicians," the FDA said.

Regulators also noted that if patients didn't register their device properly, physicians were unable to access their data.

"iRhythm takes these matters very seriously and intends to respond within the specified time period and work diligently to address the FDA's comments," an iRhythm spokesperson wrote in an email to STAT.

The FDA requires a response from iRhythm within 15 days, but does not mandate iRhythm take its devices off the market.

The letter has hurt iRhythm's stock prices, but Margaret Kaczor, a William Blair analyst following iRhythm, expects them to bounce back once the company has responded to the FDA. The company may need to submit another application for the updates to its device through the 510(k) pathway requiring that companies prove substantial equivalence to another device on the market.

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"We do think this is going to be something that is manageable and that there won't be a significant change in usage, especially longer-term," Kaczor said.

The FDA routinely issues warning letters to enforce patient safety, but regulators holding a digital health company accountable for making unapproved claims and changes remains rare. The FDA has only recently begun seriously regulating digital health technology, particularly in the artificial intelligence space. Multiple investigations by STAT have found that software tools can deliver inaccurate results that advise doctors poorly, send false alarms, and add bias into health care.

"The warning letter is a clear message to industry that FDA will enforce against manufacturers when changes are made to software that could impact safety and efficacy of the device," said Kyle Faget, a health care and life sciences lawyer with Foley & Lardner LLP.

It's burdensome to submit every algorithm change to the FDA, however, especially when it comes to AI, which learns and improves itself from real-world use. The FDA proposed a new pathway, called the "predetermined change control plan," earlier this year. The program would allow developers to submit all their planned algorithm modifications upfront.

Waqaas Al-Siddiq, CEO and founder of heart monitoring company Biotricity, said the warning letter is a wake-up call for companies in the space to be overly cautious when submitting to the FDA. He's also hoping that, as a competitor of iRhythm, the enforcement action will create opportunities for other players, particularly those with rechargeable batteries that don't have a transmission limit.

"There's going to be a lot more conversation around what is the right product and technology to support the patient," Al-Siddiq said.

Medical Devices Reporter

Lizzy Lawrence is a medical devices reporter at STAT.

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