The Apple Watch ECG/EKG detected something strange about my heart rhythm, cNet
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M. Taylor
2018-12-07 05:28:27 UTC
The Apple Watch EKG detected something strange about my heart rhythm

The latest update, WatchOS 5.1.2, rolled out two new heart features that
could help warn users of life-threatening conditions.
By Vanessa Hand Orellana, December 6, 2018 6:01 AM PST

When I first started testing out the new EKG feature on the Apple Watch
Series 4 -- available Thursday via the free Watch OS 5.1.2 software upgrade
-- the last thing I expected was to find something abnormal with my heart
rhythm. But that's exactly what happened when I was cross-referencing the
Watch's readings with medical-grade EKG equipment at the doctor's office.
"We see on your Apple Watch the same early heartbeat that we see on the
EKG," said Dr. Gregory Marcus, professor of medicine and a cardiac
electrophysiologist at UCSF Medical Center as I sat on the hospital bed with
cables attached to my body and an Apple Watch Series 4 on my wrist.

The results from the Apple Watch EKG showed the same irregular beat as the
doctor's EKG.

"These early beats are very common . but they can lead to problems in the
long term. So we should talk a little bit more about that," he added.
Heart-rate tracking has always been a big part of the Apple Watch and
fitness trackers in general. But until now, it's mainly been used for
activity tracking and calorie counting.
With the update to Watch OS 5.1.2, heart rate will play a more important
role on the Apple Watch as we get access to the two new FDA-cleared features
that Apple announced at its September keynote. There's an abnormal heart
rhythm alert for all Apple Watches, except for the first-generation model,
and an electrocardiogram (EKG or ECG) exclusive to the Series 4. Both of
which could help warn of potentially life threatening heart conditions.

Video: We tested the Apple Watch EKG against a hospital EKG
Measuring heart rate
Heart-rate tracking isn't new to wearables. Smartwatches and fitness
trackers have for years used LEDs and optical sensors on the back to measure
the changes in blood flow under the surface of the skin, aka your pulse.
When the heart beats, more blood gets pumped into the blood vessels
absorbing more light. Between beats when there's less blood, more light gets
reflected back into the receivers of the watch.

In 2017, the Apple Watch became proactive about how it used heart rate
information by adding the high heart rate notifications to the watch which
let users know when their heart spiked above a certain level and later added
the low heart rate notifications. These notifications had already been
helping users detect serious conditions.
But the heart rate only measures beats per minute, or the frequency of the
heart beat over time and not the patterns between each beat known as heart
"You can have a regular rhythm that is very fast or too slow . And
similarly, one can have an irregular rhythm that is of a normal rate, that
is too fast or too slow," said Dr. Marcus.
With the new Irregular rhythm notification, the Apple Watch uses the optical
sensor to measure heart rhythm and alert users when it detects an irregular
pattern that may be atrial fibrillation (aFib), a type of arrhythmia that
can increase your risk of stroke and other serious heart complications. This
feature will only work for adults over the age of 22 and won't help if
you've already been diagnosed with aFib.
EKG on the Apple Watch
To make a definitive diagnosis, a doctor needs more information than what
the pulse can provide.

"Sometimes those beats are so early that the heart hasn't had adequate time
to fill, even though electrically there may be an early beat that's
happening," said Dr. Marcus. "We would want to have an electrical
confirmation of a diagnosis of atrial fibrillation before we decide on
acting on that and not base it in general, on the pulse recording alone," he

That's where the EKG comes in. An EKG uses electrodes to measure the
electrical activity that results from each expansion and contraction of the
heart. A hospital grade EKG generally consists of 10 electrodes placed on
different parts of your body. While the Apple Watch Series 4 has two: One
electrode on the back crystal and one electrode on the digital crown.

"This 12 lead EKG shows what's happening electrically in the heart from 12
different perspectives, or 12 different directions, whereas the Apple Watch
gives you that same electrical activity, but really in just one direction,"
Dr. Marcus explained.

As he was looking at his monitor, I opened the new EKG app on the Apple
Watch Series 4 to take my first EKG. I put my finger on the digital crown
and waited while the screen counted down 30 seconds. The Apple Watch
classifies your heart rhythm as either AFib, sinus rhythm or inconclusive.
My result: inconclusive.
The notification on the Apple Watch also said I should contact to my doctor
if I didn't feel well or if I continue to get the same result. Users can
share these results as a pdf with their doctors, but luckily my doctor
happened to be standing next to me.
The EKG on the Apple Watch directly coincided with the results of the
hospital EKG Dr. Marcus had printed out. There were intermittent early beats
coming from the upper right ventricle of my heart.
"This would be really useful to screen for this or to have the first
understanding that you have these early heart beats," said Dr. Marcus.
"What's missing in the single lead Apple Watch is the information that tells
us more specifically where exactly this is coming from."

More information equals faster results
Dr. Marcus says I probably won't die because of what he found on my EKG, but
he does want to see me to follow up about my early heart beat, something I
likely wouldn't have caught without this kind of test. And for people with
more serious heart conditions, this could help doctors make a faster a
diagnosis and allow them to treat the problem sooner.
"Some people feel it when they have atrial fibrillation, but a lot of people
don't. So there's this hope that we might detect those people who otherwise
didn't know they had atrial fibrillation," said Dr. Marcus.
The Apple Watch is the only direct to consumer device with a built in EKG.
But there are other devices like Alivecor's FDA cleared KardiaMobile and
KardiaBand for the Apple Watch that give users access to an EKG outside of
the doctors office. Apple watch competitors like Garmin and Fitbit are also
working to improve their heart rate monitoring as more tech companies focus
on healthcare as a way to breathe new life into wearables.
"The flip side is that we recognize there's a risk of false positive results
which could lead to undue anxiety," said Dr. Marcus.
The irregular heart rhythm notification is already available on all Apple
Watches starting with the Series 1 and can be set up in the Heart section of
the Watch app. The EKG app is only available on the Apple Watch Series 4 and
is only available in the US, although Apple expects to get regulatory
approval for this feature in other countries later on.

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