
What normal and abnormal heart rhythms look like on an Apple watch - brandonb
https://blog.cardiogr.am/what-do-normal-and-abnormal-heart-rhythms-look-like-on-apple-watch-7b33b4a8ecfa
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brandonb
OP here.

Many of you have helped out with the mRhythm Study we launched a couple of
months ago:

[https://itunes.apple.com/us/app/cardiogram/id1000017994?ls=1...](https://itunes.apple.com/us/app/cardiogram/id1000017994?ls=1&mt=8)

[https://mRhythmstudy.org](https://mRhythmstudy.org)

We're planning to start publishing some of the insights we're learning from
the study, and we thought we'd kick off with a post on the foundations:

* How normal rhythm varies and why an "irregular pulse" is actually normal 

* What optical heart rate sensors measure, and how they're different from the ECGs commonly used in hospitals. 

* An example of an "irregularly irregular" abnormal heart rhythm. 

* An example of a regular abnormal heart rhythm (atrial flutter) 

* An answer to one of the most common questions we hear, "Could Apple Watch detect heart attacks?" (Short answer: not yet.) 

If you have questions or things you're curious about for the next few posts...
we'd love to hear your thoughts!

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Mahn
I know this is probably not the feedback you are looking for, but: your page
at [http://www.mrhythmstudy.org/](http://www.mrhythmstudy.org/) uses a non-
standard font (Avenir Next) which doesn't show up in Windows; instead what I
see is an ugly Times New Roman everywhere that makes the page look like it
comes straight from the Geocities era. Use something like Google Fonts to
embed a custom font to fix it so that every client downloads a copy of the
font before displaying it.

~~~
brandonb
Thank you! That is helpful feedback.

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kendallpark
As a med student/programmer, I thoroughly appreciate this write up. Excellent
job, OP.

A funny aside: many of my classmates own Apple watches/Fitbit HRs. I've heard
of at least one student looking back at her heart rate data from finals week
and saw spike to 120 bps that was maintained throughout one of our more
stressful 8-hour exams. Her fitness tracker registered it as "exercise."

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danjayh
Having been in A-fib several times in my life, if you ever feel like your
heart rate isn't steady and isn't changing in the usual way as a result of
exertion, GO TO A DOCTOR IMMEDIATELY. Lesson learned. If anyone ever releases
a watch that can identify conditions like this with a great deal of
specificity and sensitivity, I would consider that far more of a killer app
than email notifications on my wrist :).

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mattlutze
You might even call it an anti-killer app...

Health monitoring is going to be incredibly helpful. Beyond just pulse
monitoring, I'm looking forward to analyzing trace materials in sweat and the
like to notice deficiencies or issues.

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sundvor
That looks like a very interesting write-up about ECG, and I'll read it
properly tonight when out of the office - thanks for writing!

I'm a Garmin Edge user of many years, always interested in HRM during
activities. But that's not something I wear all the time. Hopefully when my
Pebble Time 2 arrives something similar can be done on that platform.

I'm intrigued to see what sort of details may be captured from such a
seemingly simple device.

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tunesmith
I've got all kinds of gaps in my cardiogram which could apparently mean atrial
fibrillation, but I suspect it more means that my watch is just crappy at
measuring my heartbeat. Sometimes when I'm out on a walk it says 60-70 when I
know I'm at 130-140. Not sure how to make my watch more accurate, it's already
strapped on pretty tight.

~~~
brandonb
That's part of what we're trying to quantify with the mRhythm Study--both the
accuracy of heart rate sensors on average, but more importantly, how to
predict in which situations and for which people the sensor is likely to work
accurately enough for clinical use.

One tip I've found: if you wear the watch slightly higher up your forearm, it
often gets a better reading than if you wear it directly on your wrist.

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simonfl
I sullied my apple watch by wearing it while playing hockey for science. AMA.

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sundvor
Does the HR graph reveal stages of grief, I mean spikes, as you realised the
damage?

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Klathmon
We have looked at my wife's data when she had a panic attack a while back. You
could almost see the exact point it started as well as when it tapered off.

It was interesting in her case to see that her heart rate jumped well before
she thought it did, and that the actual "trigger" to her attack may not have
been what she thought it was.

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sundvor
That's very interesting about physical triggers happening before the perceived
start of the incident.

Agoraphobia? Best wishes for working through that, it certainly takes a lot of
time but you can get there (or at least to a state where it doesn't happen as
often).

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googleapple1
Looking forward monitoring via Apple Watch not just user’s iPhone battery with
the app like this:
[https://itunes.apple.com/us/app/watchmybattery/id1024068907](https://itunes.apple.com/us/app/watchmybattery/id1024068907)
, but the gas-tank

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steaminghacker
i thought you needed three electrical connections for ECG?

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brandonb
Any circuit through the heart is enough for (at least a single-lead) ECG. For
example, the AliveCor is a hand-held mobile phone case—when your left hand and
right hand are both touching it, you can get an ECG.

Chest ECGs done at the hospital are often 12-lead, and those give different
"angles" through the heart, which gives cardiologists more clues on exactly
which parts of cardiac tissue are causing a problem.

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robbiep
Well the 12 lead is more finnessed than that - essentially without a 12 lead
your ability to definitively rule out an acute heart attack is completely
impaired. 5 lead ECGs will still miss (some high percentage, above 10% and
below 50%) of heart attacks.

A one (two?) lead ecg as you describe is not going to tell anyone what is
going on with ST segments, particularly as you would be only looking at your
aVR or aVL(depending on which way you sum the currents).

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JshWright
The augmented leads (aVR, aVL, and aVF) require a minimum of three electrodes
(multiple electrodes are connected to ground).

An electrode on each arm gives you Lead I.

Lead I is not as useful as Lead II, but it's still plenty useful for
diagnosing all sorts of cardiac issues (there's a lot more that can go wrong
with your heart than just an MI).

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forgotpwagain
Presumably a single lead would still be able to detect certain arrhythmias?
I.e. if there are no QRS complexes, then there may be something wrong with the
person wearing the device. There are benign explanations for why the signal
might be weak but also lethal causes like Vfib -- with a few additional, I
don't think it's implausible for a device to be able to make the decision to
ask the user "hey, are you okay?" and then potentially seek help if the user
doesn't confirm that they are OK within some set period.

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JshWright
Absolutely. Consider the fact that an AED only has one lead to work with, and
it is able to recognize a couple different lethal arrhythmias in order to
deliver a shock (and more importantly, _not_ deliver a shock at any other
time).

To be clear, by "lead" here, I mean a pair of electrodes. A single electrode
(like you might put on a watch) is useless.

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meeper16
Apple does not save lives. Neither does their watch.

