Apple Says Devices May Disrupt Pacemakers: A Lesson on the Importance of EMI | Hacker News Reader

Apple Says Devices May Disrupt Pacemakers: A Lesson on the Importance of EMI

allaboutcircuits.com

33 pointsWaitWaitWha29 comments

The premise of this article is completely wrong. The assertion is that EMI (electromagnetic interference, which is caused by radio waves) is causing problems with pacemakers, when in reality the issue is simply magnetism. Pacemakers are designed to be disabled when a magnet is placed at a certain location, and the magnets in the iPhone happen to be in that spot when placed in a shirt pocket.

The article only vaguely hints at this, while instead trying to falsely link regular magnetism created by fixed magnets to the idea of EMI resulting from wireless charging. This is either intentional on the part of the author, or so poorly researched that it should be removed.

> This is either intentional on the part of the author, or so poorly researched that it should be removed.

It's rather worrisome that it's so difficult to tell the difference in 2021. I'd 100% believe you if you said that this was some conspiracy theorist looking for more ways to peddle their EMI/EMF scare stories.

With that said, I suspect this was a misinterpretation of the Apple KB [0]. From the KB:

> Magnetic interference and medical devices

> Under certain conditions, magnets and electromagnetic fields might interfere with medical devices.

I suspect the author made an accidental leap from "interference caused by an electromagnetic field" to EMI.

- [0] https://support.apple.com/en-us/HT211900

I can possibly see this as a misunderstanding of the Apple KB from a lay-person who happens to be reading it, but it’s unacceptable from someone who is publishing an article about it, especially on a site seemingly dedicated to electronics.

The more I think about it, the more this seems like some kind of content stuffing for spam, SEO, or maybe some other nefarious purpose.

I did find it interesting that the author has a significant number of posts on the site but only 3 followers. That might say more about the site’s community than the author, but something does seem odd/off.

Magnet in Apple devices is not EMI. How do I know? I had to certify one device for EMI.

Magnets cause no harm to pacemakers, though a large enough magnet could disable it permanently (that would have to be a really strong, large magnet, though).

Pacemakers are designed so that they are disabled by magnet. This is used in case the device malfunctions. Rather than cut up the person in a hurry, you can just use a magnet to stop the pacemaker from causing damage.

Any person that wears pacemaker will know how it works and will not put any electronics in their shirt pocket.

Here you can see pacemaker teardown on EEVblog, showing the reed switch that responds to magnet to cut power to the device: https://youtu.be/sNW3Xqtgkus?t=696

Magnets were chosen for this because they are universally available and if you wear a pacemaker that misbehaves it is easy to find magnet or ask somebody else to find a magnet and bring it to your chest.

A magnet does not always switch the pacemaker off. For pacemakers that are vital, the magnet usually switches to a safe mode, e.g. some fixed non-adaptive frequency and voltage. Frequency and voltage are chosen in a way that the patient will not suffer injury from it and have sufficient circulation to survive. However, due to the necessary higher frequency and pressure when standing up, walking, those things will lead to weakness, fainting, dizzyness and all the other symptoms of low blood pressure. Safe mode will keep you alive, but it definitely won't be fun.

I have to use simplified language sometimes to get the point across.

I could write all day how I work with electronics, have my own laboratory, what the EMI is and why exactly magnet is not one, but by the time I would get to the point most readers would already either fall asleep or would just look at the huge article and skip to another post.

Yes, pacemakers became more complex devices but at least the older ones work as I described and for the newer ones it is enough approximation. It is not like you can do anything else or anything different if one misbehaves.

This isn’t “EMI” at all - this is putting a magnet next to a magnetically sensitive device. Just because “EMI” has the substring “magnet” doesn’t mean they’re the same thing. This could happen with any kind of magnet.

EMI specifically means interference introduced by electromagnetic waves - not problems introduced by a static electric or magnetic field.

Further, it's not that the magnet 'hurts' the pacemaker or device in any way. The presence of a magnetic field is used as a control signal to change the operating parameters of the device.

This is critically important for a device that may not have any remote control functionality or easy way to reprogram it other than 'cut up the patient'.

(Keep in mind that these things were designed decades ago, and 'RF remote control of pacemaker' probably introduces more problems than it solves, even today.)

Has much changed in the pacemaker world since this article was published, warning of the potential for hackers controlling pacemakers remotely?

https://www.cbc.ca/news/world/cybersecurity-heart-devices-im...

There's now FDA guidance on cybersecurity risks, but in a nutshell, it says "you must consider cybersecurity risks in your risk management plan." Manufacturers were (usually) doing this anyway but the probability and impact have been reassessed since the various lawsuits.

I don't work on pacemakers, specifically, but I'm confident you can no longer say "it has RF remote and nobody can buy the programming interface, therefore it's secure", because that's what went wrong before.

Instead, the risk management plan will look something like:

1. "magnet only with big disclaimers" (because you need the emergency cut-out switch; 'patient died because malfunction' is a worse outcome than 'maybe someone put a big-ass magnet on someone's chest and they got mostly non-life-threatening symptoms')

2. optionally, some form of 'secured' RF interface. Don't presume SSL. This is risk management, remember, so it's probably enough to say "hold a magnet on and then we enable unencrypted unauthenticated comms". Or maybe they do use SSL and just put way bigger micros in there. I don't know.

(edit: someone below who knows more than I do says "use Bluetooth", possibly triggered by magnet taps. Makes sense to me.)

Regardless of the fact that this is not EMI, putting a strong passive magnet in a phone is just asking for trouble. Not only can it interfere with medical devices, but it will also gather up iron particles in the environment that will scratch up the back of your phone.

I use a wireless charging pad regularly and have no trouble aligning the phone. It's not like the alignment needs to be perfect, it can be an inch or more off-center and it will still charge fine. I think the solution is worse than the problem here.

> it will also gather up iron particles in the environment that will scratch up the back of your phone.

Interesting theory, but I haven’t seen any evidence of this actually happening in the wild.

Side note - qi charging is only one of the useful aspects of MagSafe phones. It makes a great car mount, and my PopSocket wallet holds on tight until I want to take it off.

There's already some popular evidence of this happening in the wild: https://www.reddit.com/r/mildlyinteresting/comments/nbru1d/t...

Do iron particles cause scratches at level 6 and deeper grooves at level 7?

> putting a strong passive magnet in a phone is just asking for trouble. Not only can it interfere with medical devices, but it will also gather up iron particles in the environment that will scratch up the back of your phone.

Not to mention the effects on the magnetic strips of credit cards, hotel keys, and other pocket-likely items one may be carrying with the phone. I'm shocked this hasn't caused more commonplace hassle if the magnet is strong enough to throw the reed switch in a pacemaker.

I don't think it's throwing the reed switch, it looks like these medical devices are using magnetic fields to control their operation.

I don't think this is so much an Apple problem as a medical device manufacturer problem. These devices disable themselves in the presence of magnetic fields. Maybe device manufacturers should consider a different disabling technology. Or alert users when their device is disabled.

I agree, the article is conflating issues. However I would not have been put off by a small pictogram in the iPhone box to not place it in your shirt pocket over your pacemaker. By remaining silent on the issue, confused grandparents are definitely going to be posting on “the facebooks” about run away the second you see an iphone

Not really sure what that pictogram would look like to convey that easily. There are safety instructions included though that mention medical device interference mitigation.

Maybe the easiest solution would be just put an NFC tag under the skin above the implant and have phones trigger an alert if they see it.

Is there a better non-connected alternative though?

I doubt an app would be set to the same standards as pacemaker hardware.

There are bluetooth enabled pacemakers and electrocardiologist can already wirelessly connect to pacemakers. I'm sure the industry can come up with something.

Pacemaker (and other medical devices, insulin pumps, neural stimulators, defibrilators) disabling or safe mode via magnet will not go away, even with more bluetooth-enabled devices. First, a magnet is easily available in any EMT's backpack for exactly that reason, and many households might also have one somewhere. Second, bluetooth control apps are extremely device-specific, so you have to find out which device you want to talk to first, then get the ultra-special, secret, expensive app from the manufacturer. Third, you need to pair your bluetooth pacemaker. How do you do that, you ask? You tap thrice with a magnet to get it into pairing mode... (or something, it depends on the device, but almost always you do something with a magnet).

Disabling is just putting the magnet permanently onto the reed contact, and that won't change because every EMT knows to do that. Other control functions are some tap-pattern.

A knocking-sequence using magnetic fields?

Apple never cared about EMI or self regulation.

When the entire industry agreed on max power to cellphone radios, apple said YOLO and used triple that.

If you were in a place where everyone had one bar, suddenly an iphone3G showed up and it would have 2 bars and everyone else dropped to zero. I mean, great for apple.

Like others said, this isn't EMI, it's induction. And almost all electronic devices are vulnerable to it. Magnetic fields cannot be blocked yet the path field lines can be redirected, this is called shielding. It's not a panacea.

https://en.wikipedia.org/wiki/Electromagnetic_shielding#Magn...

https://en.wikipedia.org/wiki/Faraday%27s_law_of_induction

This isn't a vulnerability of the pacemaker; it's a feature.

A feature can be a vulnerability...

Well... to a minor degree, it's also a vulnerability. In fact, it would make a good plot for a murder mystery - the murderer triggers conditions where the victim's heart would totally freak out (maybe high emotional stress) so that the victim is absolutely dependent on the pacemaker to keep them alive, and the murderer also has a magnet in the right place to stop the pacemaker. After the victim dies, the murderer walks away with the magnet, leaving no trace of what happened.

But, you know, that's not an easy vulnerability to exploit...

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