How do you get a decent ECG with a wearable that has a single point of contact with the skin. If you need to touch a contact on the device to get a two lead equivalent ECG then how can this be real time monitoring?
By krunck 5 days ago
Real-time monitoring and continuous monitoring are different goals. The use case for something like this is probably a wearer who is experiencing heart palpitations, and has the time and clarity of thought to actually find the correct app on their device and start recording.
Continuous monitoring is extremely challenging still because ECG data needs to be sampled at a relatively high frequency (~200 Hz) to accurately identify the QRS complex in the waveform. That uses a lot of power, and the batteries we have still aren't good enough to support those types of demands. 200 * 60 * 60 = 720,000 samples per hour to collect and process.
It's possible that algorithmic approaches may be able to reduce the sampling frequency required. Power-constraints were the main issue when I studied this topic 10 years ago during my master's degree. I had looked into non-frequency domain techniques (such as empirical mode analysis/Hilbert-Huang transform) as a possible way to reduce sampling frequency and thus power consumption.
There are audio recorders like TileRec by Attodigit that can record for 30 hours on a single charge and voice is recorded at 16khz and compressed live to mp3 and is super tiny at 0.5z. I’m thoroughly unconvinced that power or complexity of handling a 200hz signal is the bottleneck. 200hz is nothing probably even to a low end microcontroller these days.
By vlovich123 18 hours ago
This is out of my specific expertise, but the AFE1291 does 8k 24 bit samples per second and uses 495 μW when sampling. That's enough to run full rate for 10 straight days on an apple watch battery (1.189 Wh was the first google result).
Integrated frontends have had big impacts on efficiency and improving batteries have had basically the same increase in specific energy. I would be shocked if power was a limiting factor.
Fitbit supports detection of Afib and has FDA approval. It’s not entirely out of the realm of possibility that one day it could also receive approval to detect heart attacks. It probably already has the data that might lead a savvy user to infer it just by looking at elevated resting heart rate, SpO2 differences, and irregular heart rhythm alerts.
By firesteelrain a day ago
My Fitbit record showing heart rate spikes to 125 was one of the things that I noticed that suggested I was having a heart attack in 2020 (I was).
By lazyasciiart a day ago
Hm, why is 125 a heart attack? Isn't that a fairly normal heart rate for exertion? Or were you just at rest?
By stavros a day ago
GP could have been having a non STEMI heart attack.
By firesteelrain 21 hours ago
I was lying down at rest.
By lazyasciiart 15 hours ago
i would imagine you could take an ekg for 1-2 seconds every 30 seconds and run it through a much more simple model to determine if it should take a longer sample, no?
rather than reducing the frequency of the sampling, dynamically adjust the duty cycle of when sampling is happening?
this is probably a dumb suggestion, it seems pretty obvious. for example the apple watch doesn’t do o2 monitoring continuously, just for some fraction of the time.
do you need to sample every second to detect heart attacks? don’t they continue to show up on an ekg for more than 30 seconds?
By sneak a day ago
> apple watch doesn’t do o2 monitoring continuously, just for some fraction of the time
Making it effectively useless? Unless the fraction of the time is multiple times per minute? E.g. in sleep apnea it's not uncommon for some desaturation to occur, triggering an arousal and deeper breaths, restoring saturation, only for the cycle to repeat 2 minutes later.
My Garmin has a similarly useless feature. I have no idea what the supposed benefit is. Maybe they hope that if they sample multiple nights they can detect some desaturation anyway and can get the user in for polysomnography? Might be worth it.
By elric a day ago
I have mild sleep apnea and my Apple Watch is the reason I figured it out. If you wear it every night, you will catch it. I have on average 1-2 events an hour. Even with that few, the Apple Watch would catch the O2 drop enough times over a month that it worried me to see my O2 drop under 90%
By jml78 a day ago
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By 5 days ago
There’s a strong history of useful signals from single lead ecgs.
Detection of ecg anomalies(especially episodic ones with intermittent recording) was the subject of the physionet cardiac computing challenge almost 10years ago[0].
It’s amazing how far machine learning has come. I know teach a version of this challenge as a one day in class activity in my department’s physiology class. They actually get to train multiple models on a gpu cluster (and compare that to trying to train models on their laptops).
One thing we reinforce in the lesson is human vs. computer “interpretation”. They/clinicians can look at ecgs and make some sense of them. An LTSM is worse than random chance/a medical student. However moving to the frequency domain makes the LTSM more accurate than cardiologists, but neither they nor clinicians can “see” afib ina spectrograph. It’s a great way to talk about algorithmic versus human reasoning and illustrate that to students.
That then gets reinforced with other case studies of the ying and yang of human and machine decision making throughout our curriculum- like alpha fold working great until you ask it about a structure in the absence of oxygen, because that’s not in its training data.
> There’s a strong history of useful signals from single lead ecgs.
But to be clear, a single lead ECG requires two electrodes at a minimum and commonly a third as ground. So a single lead ECG will have minimum two cables attached to electrodes on the patient. The placement depends on which lead (eg lead I, lead II, etc) but there's always two minimum.
By closewith 20 hours ago
Article seems very light on details. Is this trying to detect ECG markers of heart attacks (like ST segment issues)? Is it somehow detecting troponin in the blood stream? How? And how are they going to prevent false positives if this is indeed a wrist-based device as I imagine it will be?
Can't read the full article. Abstract mentions 92% accuracy. That could be abysmal depending on how it's calculated? Correctly identifying 92% of heart attacks and missing 8% might be pretty good. But reporting false positives 8% of the time would be awful.
By elric a day ago
I suspect it's probably worse than that in reality. From a quick search on state of the art ECG results (the full system of leads attached all over your torso) it looks like around 90 percent specificity (True negative rate) and under 50 percent sensitivity (true positive rate). So it's only pretty good at ruling out heart attacks, but still misses them sometimes. But is pretty bad when it comes to false alarms. I think they use it along with multiple other tests and consideration of symptoms in triage at the hospital.
By absolutelastone 16 hours ago
Even 'return false' would best 92% accuracy.
By bobmcnamara 21 hours ago
Yes, global afib prevalence is about 1-2%, so return false would be 98-99% accurate, which is why accuracy is not a metric used to assess medical diagnostics.
However, the sensitivity of return false is 0%, which renders it useless (and why sensitivity and specificity are used in this context).
By closewith 19 hours ago
Is the ECG for a heart attack the same for women and men?
The symptoms aren’t.
By croes 17 hours ago
The most common heart attack symptoms are the same for men and women. The less common, less diagnostic symptoms are more common in women. Over time the medical opinion has swung back and forth (eg thinking women had less pain, until it was recognized that many men have heart attacks without pain) but the current consensus is that the important symptoms are pretty much the same between men and women. Women may be more likely to experience nausea during a heart attack, but you can't use nausea to diagnose a heart attack and men get nauseated a similar amount. These symptoms also don't take into account body types, which have a big impact on the type of attack and symptoms.
Men and women have slightly different ECGs and a doctor can usually tell your gender from an ECG. The appearance of a heart attack will be more similar than a normal heartbeat. Gender differences have a much smaller impact on an ECG than things like body mass and blood pressure. Overworked hearts will look more like overworked hearts.
By hwillis 16 hours ago
Awesome
By neiesc 19 hours ago
This kind of technology has been technologically viable for decades. The fact that we’re only now seeing prototypes, not mass adoption, is an indictment of the legal framework around medical devices.
The FDA classifies these devices as high-risk because they might give a false result but completely ignores the guaranteed harm of not having them at all. It’s a system that punishes action and rewards delay.
They allow a summary report. They don't require a clinical human trial. They barely care if you follow the FCC and safety requirements for electronics in general. This does not look burdensome.
By hwillis 15 hours ago
There’s no “might” here, in a device advertised as “92% accuracy”. This device _will_ give false results, almost certainly an overwhelmingly number of false results relative to the actual heart attacks it detects. And those false results have real, guaranteed harm and cost as well.
Both false positives and false negatives are harmful. False positives will send people to the hospital for no reason and divert resources from people with real emergencies - not to mention leaving them with a large ER bill to pay. False negatives will result in people with actual heart attacks dismissing their symptoms and dying.
By avalys 19 hours ago
The counter is that people can build their own informed intuition about whether these things are helpful, particularly in coordination with their doctor and experience of using it. And a product is easier to improve and will improve more quickly if the company can easily bring updates and find investment that improve quality to product they have revenue for.
I think the FDA safety margin for things like this should be more “this has no actual obvious harm to use, it has a plausible mechanism of action to help + isn’t fraudulently measuring what it claims to measure and its science backed.
Something like this hits all the targets already.
By vlovich123 18 hours ago
I agree the legal restrictions (and liability) should be looser. But other countries are pretty bad about this too in my experience. It's more of a medical establishment monopoly thing it seems.
Also you can already buy home ECG devices for a couple hundred bucks. Not sure if there is some history of being banned in the past or whatever, but otherwise I'd guess the main problem is just a lack of much interest in the market.
By absolutelastone 16 hours ago
>is an indictment of the legal framework around medical devices.
Well medical devices aside, the legal framework around anything, including business, manufacture etc. is more impeding while failing to address things like environmental destruction/pollution which causes real harm. ( notice, that I did not say climate change, a separate subject).
It all makes sense when one sees it either though the lens of either corruption of more likely human stupidity - where a bunch of rules give people the comfort of being protected.
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