The Apple Watch Series 4 Announcement

Last Tuesday, Apple announced the latest model of their wildly popular Apple Watch. Called the Series 4, the new device has the usual range of tweaks and upgrades, like a better processor and new display. But it’s the health-related features that have us (along with a big chunk of the tech and healthcare industries) really interested. Indeed, in a typically slick display of marketing savvy an showmanship, Apple COO Jeff Williams called the device “an intelligent guardian for your health.”

The announcement has implications for the healthcare industry as a whole, as yet another step forward for a tech company that’s made no secret about its health-related aspirations. The Series 4 could also be considered emblematic of the move towards a consumerized healthcare experience.

New features

Apple added several intriguing health features into the Series 4. In particular, the watch will now send an alert if the wearer’s heart rate is too low (it previously only did this when the heart was beating too fast). In addition, the same sensor that reads heart rate is now used to detect atrial fibrillation, again alerting the wearer if a potential problem is detected and suggesting a call to the doctor.

Finally, the engineers added yet another sensor to the watch, this one electrical, giving it the ability to generate an electrocardiogram. Now, anyone can track their heart rhythm and get a lead on potential cardiac problems without leaving the couch.

The first, sorta

Williams touted the Series 4 as the first-ever FDA-cleared, over-the-counter, direct-to-consumer ECG. It’s true. Partly. In fact, as numerous outlets have reported, AliveCor already released the FDA approved KardiaBand that works with the Apple Watch. However, as CNBC reporter Christina Farr noted on Twitter (HT to AppleInsider for the link), the KardiaBand requires a physician to check the ECG reading before making it accessible to the user. And, according to William’s comments during the keynote, the Series 4 went through the de novo approval pathway, which the FDA uses for devices that are considered first of their kind.

Having a built-in feature rather than an accessory matters for a couple of fairly obvious reasons. First, because it’s available to anyone with the device, not just a few people willing to shell out the extra $199 for KardiaBand (on top of the $399-$499 price of the watch itself). Second, it’s a feature that one of the world’s largest companies feels is important enough to go in on and work with regulators to clear. This is serious, indicating CEO Tim Cook and Co’s increasing focus on healthcare.

According to Brennen Hodge, Founder of Citizen Health, it’s a signal to the rest of the market:

“While there are many smartwatches/wearables already on the market claiming to measure ECG, the Apple Watch announcement is huge for the wearable industry. Having a company as prominent as Apple enter this market is a signal to all device manufacturers that wearables aren’t just simply “fitness/activity trackers” anymore. These devices are becoming medical tools that have the potential to save lives.”

How it works

Key to the new Apple Watch is that addition of an electrical sensor noted above. Most wearables, including the Apple Watch, use an optical sensor and a technique called photoplethysmography (PPG) to measure tiny changes in blood volume through the skin. Changes in blood volume in capillaries indicate heart rate. PPG can also be used to look at heart rhythm. A recent review in the Canadian Journal of Cardiology stated that

“several studies have suggested a role in using PPG in arrhythmia detection. In a proof-of-concept study, PPG can be used to identify potentially life-threatening arrhythmias with a true positive rate of 93% and true negative rate of 54% […]”

The same review mentioned the use of the (older) Apple Watch to detect sinus (normal) rhythms vs atrial fibrillation. Now, the Series 4 formalizes that functionality to alert the wearer they might be experiencing a-fib.

With the new sensor, though, the watch can run an actual ECG. That provides a different level of detail to look at cardiac function. As the American Heart Association puts it, an ECG can determine” if the electrical activity is normal or slow, fast or irregular.” In addition, the test can indicate “if parts of the heart are too large or are overworked.”

The technology underlying consumer-based ECG devices has – obviously, based on the FDA clearance – reached a point where it’s accuracy is quite impressive. The CJC review notes that AliveCor’s devices “interpreted atrial fibrillation with 93% sensitivity [e.g., true positives] and 83% specificity [e.g., true negatives].” Kate Sheridan at STAT News got her hands on an overview of the numbers from Apple’s FDA application. In a study of people, half with a-fib and half without, “the app was very accurate: It caught more than 98 percent of people with atrial fibrillation, and correctly told people that they didn’t have the condition 99.6 percent of the time.” In other words, aside from the roughly 10% of rhythms the app couldn’t interpret, it works really well.

Still, Sheridan points out that the app’s “positive predictive value,” which suggests the odds that a “problematic reading” is real, is 45%. In other words, “More than half the time the app flags a problem, then, the app will be wrong.” This is attributed to the fact that, despite being the most common arrhythmia, atrial fibrillation is relatively uncommon in the general population and in those situations, “even a very accurate test” will frequently return a false positive. Therefore, as with anything medical, someone receiving an alert from their Apple Watch or any other wearable should speak with their physician.

That’s what Apple came up with and a little bit about how it works. In the next post, we’ll look at what it means for the people involved – the clinicians and the patients/consumers.

Next up, Part 2: What the new Apple Watch means for patients and clinicians

Part 3: What the new Apple Watch says about the consumerization of healthcare

Photo by rawpixel on Unsplash

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