Smartwatch Shows Promise in Detecting Heart Problem
March 21 2018 - 12:32PM
Dow Jones News
By Peter Loftus
Smartwatches could detect a common heart-rhythm disorder with
relatively high accuracy when people were at rest, but less so when
participants were physically active, a new study found.
The study, led by researchers at the University of California,
San Francisco, tested the use of the heart-rate sensor and step
counter built into Apple Inc.'s Apple Watch, to try to detect
atrial fibrillation, a type of irregular heartbeat that can cause
blood clots and strokes if left untreated. Researchers used a
mobile application from Cardiogram Inc. -- which provided funding
for the study -- to access the watch data, and a machine-learning
network trained to analyze the data.
About 2.7 million Americans and 34 million people world-wide are
estimated to have atrial fibrillation. Many patients don't
experience symptoms, and it can go undetected until a complication
occurs. Researchers say earlier detection could get patients on
treatments like blood thinners to reduce risk of complications.
The study is part of a growing body of research testing mobile
devices such as smartphones and watches as tools to monitor users'
health and potentially intervene to improve outcomes. But the
approach has limitations, including patient demographics that don't
always represent the broader population -- partly because of the
high cost of some devices. The Apple Watch costs between $249 and
$399.
The new UCSF study is part of a broader project it started in
2013 called Health eHeart, which is trying to harness mobile
technologies to develop new strategies for preventing and managing
heart disease. It has enrolled about 160,000 study participants and
is aiming for up to one million people.
For the new analysis, researchers developed a type of machine
learning known as a "deep neural network" to analyze the heart-rate
and step-count data collected from about 6,680 of the study
participants who had Apple Watches. The researchers used step-count
data to assess whether increases in heart rates were normal due to
physical activity or irregular.
Researchers provided Apple Watches to about 50 patients with
atrial fibrillation while undergoing procedures at UCSF known as
cardioversions to restore normal heart rhythms. Patients were flat
on their backs and the watches collected heart-rate data while they
were still experiencing irregular heartbeats, and then when normal
heart rhythm was restored.
The algorithm was able to distinguish between atrial
fibrillation and normal heartbeats with about 97% accuracy when
compared with gold-standard electrocardiograms, according to
results published online Wednesday by JAMA Cardiology.
"We've shown a proof of concept that it's very likely that these
commonly worn devices will ultimately be very useful in helping to
screen for atrial fibrillation," Dr. Gregory M. Marcus, a UCSF
Health cardiologist and senior author of the study, said in an
interview.
But the results were less impressive in a test of the algorithm
in about 1,620 people using Apple Watch outside of the hospital in
their everyday lives. The watch distinguished between atrial
fibrillation and normal heart rhythm with about 72% accuracy,
compared with participants' reports to the researchers of whether
they had atrial fibrillation. That means there were a significant
number of false positives and false negatives.
Researchers said it was more difficult to detect atrial
fibrillation in active people because activities can vary heart
rates, and the watch measured heart rates less frequently than in
the hospital setting.
"The result is indeed humbling, indicating far more
misclassification and lower positive predictive value compared with
gold-standard" ECG's, Mintu P. Turakhia, director of the Cardiac
Electrophysiology program at the Palo Alto VA Health Care System,
wrote in a JAMA Cardiology editorial accompanying the study.
Consumers can't now use the Cardiogram app to detect whether
they have atrial fibrillation, said Brandon Ballinger, co-founder
of Cardiogram. He said the company hopes to begin adding features
later this year to identify people at risk of atrial
fibrillation.
Apple didn't participate in the UCSF study. The company
announced last year the start of its own study with Stanford
University researchers to assess the ability of Apple Watch to
detect atrial fibrillation.
--Tripp Mickle contributed to this article.
Write to Peter Loftus at peter.loftus@wsj.com
(END) Dow Jones Newswires
March 21, 2018 12:17 ET (16:17 GMT)
Copyright (c) 2018 Dow Jones & Company, Inc.
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