The newest version of the Apple Watch will feature a heart monitor app that can do a form of an electrocardiogram. Many have greeted this announcement as a great leap forward for health. The president of the American Heart Association even took part in the product launch. For a more measured response, it's worth looking at potential downsides, and it turns out there are a few. That's the topic of this week's Healthcare Triage.

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The upside potential is twofold. First, doctors could monitor at a distance how patients with known health problems are functioning outside the office. Second, the device could diagnose heart problems in people who don't know they have them, picking up abnormal heart rhythms earlier than would otherwise be possible.

But, with respect to monitoring from a doctor, the Food and Drug Administrations "cleared" the app, an easier hurdle to surmount that "approval." But, it specifically said people with diagnosed atrial fibrillation, one of the most common heart arrhythmias, should not be using the app.

If that's the case, the major potential for the device is to pick up arrhythmias in otherwise healthy people. That's still a big selling point. Picking up abnormal function earlier could theoretically lead to improvements in health, such as reductions in strokes. 

But, just because something seems like a good idea, it doesn't mean it is. No screening test is perfect, as we've covered in many episodes of Healthcare Triage. In the simplest sense, whenever we consider the results of a medical test, they can be positive or negative. In general, we would like people who are sick to have a positive screening result, and people who are well to have a negative result. Unfortunately, people who are sick sometimes have a negative result. Those are false negatives. People who are well sometimes have a positive result. Those are false positives.

Both of these outcomes are worrisome. A false negative might leave someone who needs medical help with a mistaken sense of assurance. Given that relatively few people have serious, undiagnosed arrhythmias with no symptoms (if people did, we would be screen for this more often), this isn't a major concern. False positives are because they cost us time and money, as well as cause emotional distress. 

The healthcare system is already busy, if not overloaded. No physician wants to field calls from patients that have no problems. Such patients will require visits and further testing, and will potentially receive interventions. They'll generate bills and harms without benefits.

The watch will have an "irregular rhythm" notification feature, which alerts people to potential problems. There's every reason to believe it will generate many false positives.

Before granting clearance, the F.D.A. reviewed data collected by the Stanford Heart study for 266 people who got such a notification, and most of the notifications were wrong. The study wasn't peer reviewed, so we don't know for sure, but this was also a population for whom atrial fibrillation might be more common than in those who might use the watches. People who buy the latest Apple Watch will most likely be younger, healthier, wealthier, and more plugged into the healthcare system, and less likely to remain undiagnosed.

This is one of the major problems with such a device: the people most in need of it, those who might benefit from test and distance monitoring, are the least likely to get it. If we truly believe that this was a medical test beneficial to the general population, insurance should pay for it. And, no one is suggesting that should happen.

In fact, many experts don't think it makes sense to have universal cardiac monitoring of the general public. The United States Preventive Services Task Force has issued a "D" recommendation for screening asymptomatic adults at low risk. The group doesn't think there's enough evidence to recommend screening of adults at intermediate or high risk. It doesn't even think there's enough evidence to recommend screening adults 65 or older, who are at higher risk, for atrial fibrillation.

The task force bases these recommendations on good research. A large randomized controlled trial of echocardiographic screening for many heart problems did not demonstrate that such screening offered any benefits in reducing death or the risk of heart attacks or strokes in middle-aged people. And these are scans much more robust than will be available with the new Apple Watch.

None of this prevented the American Heart Association from heralding this new function. Although, it's not clear where the groups enthusiasm comes from. Doctor Ivor Benjamin, the association president, appeared at the official announcement of the watch and praised the advancement for tools that, and I'm quoting, "help fight heart disease." The AHA does not officially endorse the watch or any specific products.

I happen to own an Apple Watch. I find the other functions useful and fun. I even enjoy aspects of the activity monitoring, but I'm under no illusion that they will help me lose weight or exercise more or improve my heart health. I own one because I want it, not because I need it. That's the same criterion you should use, too.

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