In September 2018, Apple released its Watch Series 4, which is equipped with FDA-cleared health features aimed at recognizing cardiac arrhythmias like atrial fibrillation (Afib). Click here to read 番茄社区's original coverage on the device release. In this article, we follow-up on what has happened with wearable devices and their health functionalities since then.
Apple's September announcement of the built-in ECG feature on its new Apple Watch Series 4 and FDA clearance for an app to detect Afib or sinus arrhythmias in adults without known arrhythmias spurred both and jeers.
The actual release of the app happened quietly on December 6.
"We are confident in the ability of these features to help users have more informed conversations with their physicians," said Sumbul Desai, MD, Apple's vice president of Health in a . "With the ECG app and irregular rhythm notification feature, customers can now better understand aspects of their heart health in a more meaningful way."
Perhaps as many as with the ECG feature reached the wrists of consumers this year, according to an analysis from the International Data Corporation (IDC), a provider of market intelligence.
While not much real-world experience with the Apple ECG app has accrued yet, the hubbub surrounding it is justified, said Anthony Pearson, MD, of St. Luke's Hospital in St. Louis, Missouri. "It now monitors your EKG, which is really quite a step forward."
Clinical Utility
Pearson has written about his clinical experience since 2013 using AliveCor's ECG add-ons for smart devices, including past iterations of the Apple Watch, for his Afib patients.
While the FDA's indication for the Series 4 Watch ECG app specifically excluded individuals with existing arrhythmia and was for informational purposes only, AliveCor's Kardia devices are for detecting Afib, including in adults with known or suspected heart conditions, when prescribed or used under care of a physician.
Having such ECG information available for long-term cardiac monitoring has helped in triaging patients, monitoring rate control after cardioversion, and avoiding pointless appointments, Pearson wrote in a blog post for 番茄社区. "We now have an instantaneous patient-controlled method for knowing what his cardiac rhythm is doing and whether he is having symptoms. This knowledge allows me to make more informed treatment decisions."
The Series 4 Watch also allows for emailing rhythm readings to a physician, but not many of Pearson's patients have sprung for the more expensive, albeit less clunky setup, he told 番茄社区.
Screening Questions
Most people who do get the $399 to $499 Series 4 Watch are in a relatively healthy population with low prevalence of Afib.
"Apple is sort of promoting this as something that can be used in the general population," noted Ethan Weiss, MD, of the University of California, San Francisco.
However, that prospect has raised real concerns about false positives and unintended harm.
There isn't much published evidence concerning how accurate the Series 4 Watch is, Pearson pointed out in an interview with 番茄社区. "How it's going to work in the overall population is very worrisome because there's likely to be -- unless it is incredibly specific -- a lot of false positives that trigger hospital visits or trigger office visits or calls to the cardiologists or the primary care physicians," he said.
One study found that an app designed to passively monitor heart rate information from an earlier generation Apple Watch was nearly as accurate as standard ECG in detecting Afib. However, when tested in a sample representative of the real world, the app did not fair as well.
A study characterizing how often an irregular pulse detected by the software is diagnosed as Afib on subsequent ambulatory ECG patch monitoring is expected to be completed in mid-2019.
But even the value of true positive notification of arrhythmia by a wearable device in the general population is not entirely clear, Weiss told 番茄社区. "Most of us are concerned that it might lead to excess anxiety and/or overtreatment with medicine such as anticoagulants if you are just screening in the general population," he said.
When it comes to his clinical practical, Weiss said, "I'm not recommending it to just every person out there as a screening tool for Afib because I'm not sure we have any evidence that we need to know that we have Afib, especially if you are really young and don't have any risk factors."
The U.S. Preventive Services Task Force (USPSTF) cited insufficient evidence in its decision not to back ECG screening for Afib in asymptomatic seniors or for cardiovascular disease in healthy, low-risk individuals. The Task Force listed among the top priorities that need to be further explored in the coming year.
"Great uncertainty exists about what [Afib] duration or burden is sufficient to treat and this has colored discussion of ECG screening," wrote Hugh Calkins, MD, of Johns Hopkins University in Baltimore, and colleagues in a recent viewpoint article in .
They argued for a middle ground of opportunistic screening with handheld ECG devices, perhaps once a year for seniors, rather than systematic population screening. This approach would largely catch persistent or high-burden paroxysmal Afib, which have a prognosis similar to that of symptomatic Afib and which few would hesitate to treat if incidentally detected at an office visit, they wrote.
Clinical Trials
So far, there has been no proof that starting anticoagulation for Afib detected by screening devices improves hard endpoints like stroke and mortality.
"The only way to convincingly settle the question about systematic screening is with a randomized clinical trial," Calkins's group concluded. "Such studies will be large and expensive. Some are under way, e.g., and studies. More are planned."
STROKESTOP involves twice daily ECG screening of elderly people with the handheld Zenicor ECG device and looks at the composite of ischemic and hemorrhagic stroke, systemic embolism, major bleeding requiring hospitalization, and all-cause mortality. The trial should be completed in March 2019.
The Danish Loop study looks at prevention of stroke and systemic emboli in higher-risk older adults by heart rhythm monitoring with an implanted loop recorder, with oral anticoagulation started for any episode of Afib detected that lasts more than 6 minutes. The data aren't expected until early 2020.
Also coming in 2019 are further results from the (mSToPS) study looking at the ZIO XT single-lead ECG patch monitor in higher-risk adults. The primary outcomes were published in early 2018 showing a higher rate of Afib diagnosis with the wearable device.
The secondary composite endpoint of stroke, systemic emboli, or MI is expected after 3-year follow-up. "We'll be able to at least have an idea of the magnitude of benefit of recognizing atrial fibrillation early," said mSToPS primary investigator Steven Steinhubl, MD, of Scripps Research in La Jolla, California.
"Even at 1 year, we know that for people who had Afib, those who are clinically diagnosed surprisingly have a much higher rate of stroke and myocardial infarction," he added. "That's a little bit artificial based on the nature of the study. So I and no one else should think that's definitive information about the proof for the benefit of screening, but it's at least consistent with the idea that if you find Afib and then do something about it, that you can improve the outcomes."
The massive, ambitious , which will delve into why people suddenly suffer from cardiac events by examining information provided by wearable devices like the Apple Watch, is ongoing.
"We have a variety of Health eHeart Study analyses ongoing that look at wearable device data and atrial fibrillation, and for other conditions including diabetes and hypertension," Mark Pletcher, MD, MPH, of the University of California, San Francisco, told 番茄社区. "Expect some results in 2019."
"Hard endpoint data will be quite important, especially as we get into prospective validation of predictive algorithms and intervention effectiveness studies; we are currently upgrading Health eHeart's ability to ascertain clinical events, which should enable us to start doing these important studies in the future," Pletcher said.