technology

Apple watch has a finger on pulse, but can’t replace a doctor


The Apple Watch has been quite successful as a smart watch. The company would also like it to succeed as a medical device. The recently published results of the Apple Heart Study in the New England Journal of Medicine show there’s still a long way to go.

An estimated six million people in the United States – nearly 2% – have atrial fibrillation, a type of irregular heartbeat that brings increased risk of events like clots, heart attacks and strokes.

A selling point of the watch is a sensor that can monitor a wearer’s pulse and potentially detect atrial fibrillation.

A group of researchers enrolled almost 420,000 Apple Watch wearers in a study. (Some of the researchers were Apple employees, and Apple sponsored the research.) Over that time, 2,161 of the study participants were notified of an irregular pulse, representing just over 0.5% of the sample.

But only 450 of the 2,161 people who were notified about having an irregular pulse returned their sensor patches for evaluation.

Of the 450, atrial fibrillation was confirmed in 34%, or 153 people. Those 153 are about 0.04% of the 420,000 participants.

Many news outlets reporting on the study mentioned a topline result: a “positive predictive value” of 84%. But this result wasn’t calculated from any of the numbers above. It specifically refers to the subset of patients who had an irregular pulse notification while wearing their confirmatory patch. That’s a very small minority of participants. Of the 86 who got a notification while wearing a patch, 72 had confirmed evidence of atrial fibrillation.

Here’s the thing, though. Experts aren’t even sure if screening is a good idea to begin with.

After all, if we felt strongly enough about detecting asymptomatic people who might have atrial fibrillation, we could screen everyone with electrocardiograms.

Moreover, the task force was focusing on a population where we might intervene: older people. Patients at high risk of stroke who have atrial fibrillation (ie, older people) might be treated with anticoagulation. For younger ones at lower risk, it’s not immediately clear how we would treat them, or if we should.

And it’s younger people who are more likely to have a smart watch.

We should be clear that we’re focusing on atrial fibrillation that isn’t otherwise noticed by patients or doctors. Those who are already diagnosed and those who are symptomatic should absolutely be managed by physicians, and many will be treated with medications or procedures.





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